Micropackaging via layer-by-layer assembly: microcapsules and microchamber arrays

FULL CRITICAL REVIEW

Micropackaging via layer-by-layer assembly:microcapsules and microchamber arrays

Maria N. Antipina1, Maxim V. Kiryukhin1, Andre G. Skirtach2 andGleb B. Sukhorukov*3

The micropackaging of chemical compounds in a small and precisely defined quantity, which can

be encased, stored, is essential for response to a specific chemical, biological or physical trigger

in a controllable manner is one of the premier challenges in the development of delivery systems.

In this review, the authors discuss the application of layer-by-layer (LbL) assemblies of

macromolecules for micropackaging and controlled release of various types of cargo. The LbL

assembly method provides unique opportunities by incorporation of different functional and

responsive layer constituents tailored into one entity. Micron and submicron sized capsules made

on colloidal templates are used for biomolecule encapsulation and enable time- and site-specific

release when triggered by pH, temperature, specific enzymes, mechanic load, light, ultrasound,

or magnetic field. In comparison to individual capsules, the authors discuss the recently

introduced micropackaging approach involving cargo loading into arrays of microchambers,

made by a combination of imprinting technology and LbL assembly. In conclusion, the authors

summarise advantages and fabrication obstacles for micropackaging in capsules and

microchambers and discuss already existing as well as potential future applications.

Keywords: Encapsulation, Controlled release, Polymers, Layer-by-layer, Macropackaging

Introduction to polyelectrolyte layer-by-layer assemblyIdeally, micropackaging and delivery systems forchemical and biomedical applications have to be easyto fabricate and possess multiple functionalities formore efficient transport of cargo to designated loca-tions in vivo and in vitro, i.e. high storage capacity,protection for encapsulated substances, targetteddelivery and controlled release mechanisms. On topof that, long-time blood circulation is of particularimportance for drug delivery in vivo. A variety oftechniques are under development to address theserequirements. They comprise liposomes, drug elutingcoatings, polymer-based systems with adhered activemolecules, block-co-polymer micelles or polymer-somes, degradable organic micro- and nanoparticles,and core/shell systems.1–3

Another promising example of a smart micropacka-ging and drug delivery system is provided by layer-by-layer (LbL) assemblies of macromolecules shaped asfilms or shells. Originating from works published byDecher, Mohwald, Lvov, Rubner, Hammond, et al.4–11

in the early nineties, LbL assemblies were utilised witha variety of macromolecules, including biological ma-terials, e.g. proteins and DNA (Fig. 1). Their formationis based on entropy-driven reactions of oppositelycharged polyelectrolytes or hydrogen bonding betweennon-ionogenic macromolecules, as well as short-rangehydrophobic interactions and specific recognition.Taking LbL assembly of polyelectrolytes as an exam-ple, the construction process starts with a polyanionlayer deposited on a positively charged surface followedby adsorption of a polycation reversing the surfacecharge. Consecutive adsorption of oppositely chargedpolymers results in formation of a stable polycation/polyanion complex in each cycle. Ultimately, a multi-layer film is achieved, whose thickness can range from afew nanometres to several microns depending on thepolyelectrolytes involved, the number of depositioncycles and the medium conditions. Multilayers posses-sing different surface charge and composition can beprepared by varying the charge density on each polyelec-trolyte. The most popular polyelectrolytes used in LbLassemblies as polycations include poly(ethylene imine)(PEI), poly(allyl amine hydrochloride) (PAH), poly(L-lysine) (PLL), chitosan, gelatin B, amino-dextran, andprotamine sulphate. They can be combined with avariety of polyanions such as those formed frompoly(4-styrene sulphonate), sodium salt (PSS), poly(acrylic acid) (PAA), dextran sulphate, carboxymethylcellulose, sodium alginate, hyaluronic acid, gelatin A,chondroitin, heparin.

1Institute of Materials Research and Engineering, A*STAR, Singapore2Department of Molecular Biotechnology & NB-Photonics, University ofGhent, 9000 Ghent, Belgium3School of Engineering and Materials Science, Queen Mary University ofLondon, London, E1 4NS, UK

*Corresponding author, email [email protected]

� 2014 Institute of Materials, Minerals and Mining and ASM InternationalPublished by Maney for the Institute and ASM InternationalDOI 10.1179/1743280414Y.0000000030 International Materials Reviews 2014 VOL 59 NO 4224

At present, LbL assembly is widely used to producefunctional biocompatible coatings and ultrathin free-standing films.

A drug delivery platform can be devised by incorpor-ating layers of drug particles into LbL assemblies. Drugrelease is then triggered upon decomposition of the filmby a specific stimulus, such as variation of pH,temperature or redox potential, illumination by light,or enzymatic degradation.9 Some of the assemblies mayincorporate pre-fabricated tiny containers with drugs,thus making hierarchical nanosystems. Layer-by-layerassemblies releasing an overall drug content of 1–5 wt-%over a span of 1–100 hours have already been applied ascoatings on bone implants or skin patches.9

In 1997–1998, an approach to fabricate nano-engi-neered capsules was introduced by a group at the MaxPlanck Institute of Colloids and Interfaces.7,8 Themethod is based on the LbL assembly of oppositelycharged macromolecules on colloidal particles. When

the template particles are dissolved or decomposed, themultilayer assembly remains as an ensemble of emptyshells. The shells’ diameter is pre-determined by that ofthe colloid template and can be chosen within the rangeof 50 nm to tens of microns. The shells’ thickness isdetermined by the number of deposited layers andusually lies within a size range of a few nanometres.These multilayer shells can be made of a variety ofdifferent macromolecules, such as synthetic and naturalpolyelectrolytes, lipids, and multivalent dyes. Hence, theconstruction is extremely modular with regards totailoring the composition of the shells. Each of theconstituents brings its own functionality to the multi-layer shells. For instance, by making the shell’s outer-most layer a polymer which contains reactive groups,such as amino groups or carboxylic groups, one can thenfurther modify its surface with specific ligands, reportergroups, or other moieties for targetted drug delivery.Weak polyelectrolytes are obvious candidates to formpH-sensitive capsules, which can be reversibly loadedand unloaded with drugs in response to pH changes.

Embedding inorganic particles within multilayer shellsenables additional functionality: clay sheets make themmore rigid; metal and metal oxide nanoparticles makethe shells susceptible to light and magnetic field.12,13 Acomparison between polymer multilayer capsules andalternative delivery systems14,15 reveals the most out-standing feature of the multilayer capsules: the ability totailor different properties in one entity thus creatingnovel multifunctional materials for in vivo and in vitromicropackaging applications (Fig. 2).

This review focuses on the fabrication of smart andversatile delivery systems by micropackaging bioactivemolecules inside LbL assemblies made in the form ofindividual shells, which are dispersed in a continuousphase or an array of microchambers sealed by the solid

2 Multifunctional capsules made upon Layer-by-layer (LbL) assembly and loaded with drugs show various functions tai-

lored into one entity. Magnetic nanoparticles and antibodies drive the capsule macroscopically into a specific region

both in vivo and in vitro. Light and ultrasound susceptible nanoparticles provide release in response to the corre-

sponding stimuli. Biodegradable shells are destroyed by enzymes

1 Layer-by-layer (LbL) assembly of charged polyelectrolytes

on surfaces

Antipina et al. Micropackaging via layer-by-layer assembly

International Materials Reviews 2014 VOL 59 NO 4 225

http://www.maneyonline.com/action/showImage?doi=10.1179/1743280414Y.0000000030&iName=master.img-000.jpg&w=429&h=257


support. The authors describe methods for tailoringdifferent functionalities within one entity, alteringcapsule mechanical properties, and controlling thedelivery and release of encapsulated molecules byvarious triggering events.16,17 The authors also discussscientific and industrial areas which can potentiallyemploy LbL assemblies as delivery microcontainers,microreactors, or sensing elements.18

Encapsulation of biologically activemolecules

Encapsulation strategiesThe unique features of LbL-assembled polymer shellssuch as: a flexible geometry, controlled dimensions, andselective, tunable permeability towards molecular pay-load enable the encapsulation of a variety of differentbiologically active molecules, among which are proteins,polysaccharides, nucleic acids, drugs, as well as largerspecies including cells and microorganisms. Significantadvances in the development of capsules of this typehave enabled the efficient loading of molecular cargo,capsule guidance, and a variety of release mechanisms,including: tunable spontaneous diffusion of cargo,responsiveness to pH and chemicals, and remote on-demand rupturing of the shells triggered by physicalstimuli such as light, magnetic field and ultrasound.19,20

The active development of LbL capsules for anticancertherapy, gene delivery, and delivery of vaccines has beencatalysed by the proven evidence of capsules’ endocy-tosis by living cells.21 The aim of this section is to give anoverview on polymer multilayer encapsulation and

delivery of the main classes of bioactive species,discussing the most favourable encapsulation routinesand additional measures undertaken to preserve activityof the biomolecules.

The ultimate goal of any encapsulation process is theeffective incorporation of a species and the provision of arelease mechanism without compromising bioactivity.Therefore, the encapsulation routine must be carefullydetermined for each particular bioactive compound,considering its physical and chemical properties, as wellas stability. The molecular payload can be incorporated ina number of ways: as a multilayer film building block,infiltrated inside capsules, pre-loaded in sacrificial poroustemplates, or used as a template for LbL assembly in aform of aggregates, or microparticles (Fig. 3). In agree-ment with the basic principle of multilayer film assembly,bioactive species can be introduced in a capsule shellduring a process of alternate complexation with comple-mentary macromolecules or species.8,22,23 In anotherapproach, alternation of medium conditions such aspH, ionic strength, temperature, solvent polarity, redoxpotential or the presence of specific chemicals cansignificantly increase permeability of the multilayer shellsto molecular payloads, enabling their infiltration throughthe polymer network driven by the concentration gradi-ent.24–33 The main concern of this loading method is thatpolymer multilayer assemblies often require drastic changesof medium conditions to become permeable, and that thesechanges can compromise the activity of the biomolecules.In a more gentle approach, bioactive molecules diffusethrough intact LbL shells towards an oppositely chargedmatrix pre-loaded into capsules. Such a matrix can be in theform of stable proteins and polymers,34 oligomer residues

3 Schematic representation of different approaches of capsule loading. Pre-loading of active species (top): assisted by a

porous inorganic template a, microparticle of cargo species is used as a template for LbL assembly b. Post-loading of

a microcapsule by changing of medium conditions (bottom)


226 International Materials Reviews 2014 VOL 59 NO 4


of melamine formaldehyde,35–37 or polystyrene38 sacrificialtemplates. A hydrogel network is a good alternative matrixfor subsequent encapsulation of bioactive species intopolymer multilayer shells.39–41

Porous micron- and submicron-sized CaCO342–46 and

mesoporous silica microparticles are widely used sacri-ficial templates in pre-loading the LbL-assembledcapsules with macromolecules. These templates, pre-saturated with active molecules of interest, are subse-quently subjected to polymer multilayer coating andlater template removal through dissolution by anappropriate solvent or chemical decomposition.

Encapsulation of polysaccharidesPolysaccharides possessing electrical charge are widelyapplied in LbL assembly of capsules designed forbiomedical, cosmetic and food applications. The mostpopular cationic polysaccharide, chitosan, is actively usedin alternation with various negatively charged polysacchar-ides, such as hyaluronic acid, alginic acid, carrageenan,47

dextrans, proteins at pH above their isoelectric point, andnegatively charged polyaminoacids.

Supported polysaccharide multilayer films are beingdesigned and extensively tested for applications related totissue engineering.48–50 LbL coatings made of polysacchar-ides have emerged as a powerful tool for the immobilisa-tion of biomolecular drugs with preserved bioactivity,enabling their use in surface-mediated drug delivery. Forinstance, hyaluronic acid/heparin LbL assemblies oncardiovascular stents made of stainless steel exhibitedanticoagulant activity and further improved haemocom-patibility of the stents by providing prolonged release ofincorporated model immunosuppressant.51 Hyaluronicacid/chitosan polyelectrolyte multilayer coatings on tita-nium bone implants demonstrated high antibacterialefficiency and promoted osteoblast functions by surface-immobilised cell-adhesive arginine–glycine–aspartic acid(RGD).52 Hyaluronic acid/chitosan polysaccharide LbLassemblies incorporating DNA can be successfully used insurface-mediated gene transfection.53 Hammond’s grouphas extensively investigated controlled delivery and releaseof various bioactive species directly incorporated intopolymer multilayer films, i.e. delivery of aminoglycosideantibiotic gentamicin by hydrolytically cleavable LbLassemblies on titanium bone implants.54

Biocompatible, biodegradable and low cytotoxic poly-saccharide multilayer capsules have been fabricatedfor delivery of secreting therapeutics (such as insulinand dopamine),36,55 anti-inflammatory56 and anticancerdrugs,34,57,58 as well as for cell encapsulation andculturing.59,60 Self-rupturing polymer multilayer capsulesassembled on dextran-based hydrogels for spontaneousencapsulation and controlled release of biomoleculeswere achieved by De Geest et al.41,61

Controlled release delivery has been demonstrated forcapsules with LbL shells assembled on the microbeads ofalginate gels pre-loaded with anti-inflammatory drugs,62

and proteins.63 The release rate from such kind of capsulescan be influenced by initial content of the activecompounds, the type of multilayer shell, and a combinationof different ratios of LbL-coated and uncoated microbeads.

In a series of publications, McShane and coworkersreported on the use of alginate hydrogels in thedevelopment of glucose enzymatic optical biosensors.Enzymatic activity of glucose oxidase encapsulated inLbL-coated microbeads of calcium alginate by an

emulsion–conjugation technique did not drop signifi-cantly over 4 weeks.64 In the most recent developments,mesoporous alginate–silica particles were used instead ofcalcium alginate hydrogel.65,66

The examples mentioned above show the role ofvarious polysaccharides as multilayer film constituentsand an absorbing matrix for spontaneous encapsulationof bioactive molecules. Dextran molecules with chains ofvarying lengths are among the most popular modeldrugs encapsulated in polymer multilayer microcapsules.With the extensive use of dextrans, important aspectsof the LbL encapsulation process such as encap-sulation efficiency and shell permeability have beenstudied24,26,41,45,67–69 (Fig. 4).

Encapsulation of proteinsProteins perform a broad array of functions withinliving organisms. In fact, protein functions are signifi-cantly more diverse than those of other biopolymerssuch as nucleic acids and polysaccharides. Protein drugsare increasingly becoming a key component of modernmedical care. Most protein- and peptide-based thera-peutics, however, have poor stability in vivo and in vitroor are unable to penetrate cell membranes because oftheir large size, that unsurprisingly makes them popularactive compounds for delivery by smart encapsulatingsystem.

Proteins possess ionisable chemical groups of differentkinds such as carboxylic groups of aspartic acid andglutamic acid; amine groups (e-amine group of lysine,CNH(NH2) group of arginine, and imidazole functionalgroup of histidine) and therefore they can been used inLbL assembly as macromolecular cations or anionsdepending on the pH of a medium. Two-dimensionalLbL assemblies have shown advantages for surface-mediated controlled delivery of growth factors andantimicrobial agents at wound sites.70–72 Tannins areknown to precipitate proteins from solution by formingintermolecular hydrogen bonds and by hydrophobicinteractions; stable capsules composed of proteins andtannins have been reported.73

Infiltration into polymer multilayer shells can be asuccessful encapsulation strategy for proteins andenzymes which are stable at extreme conditions. Forinstance, urease was encapsulated in PSS/PAH multilayershells in a 1 : 1 ethanol/water mixture.27 The solvent-induced formation of pores in the shells was reversible, sothat the enzyme was retained by the shell after washingout the ethanol. In the case of urease, the presence ofethanol had a minor negative effect on its enzymaticactivity, which was found to be lower than the activity offree urease in an aqueous solution. Alpha-chymotrypsinwas determined to retain a high activity after pH-inducedencapsulation in PSS/PAH multilayer shells.35 Proteinscan also be included in polymer multilayer shells in a formof LbL-coated aggregates.74,75

Growth factors exhibit optimal proliferative efficacywithin a certain concentration range. Moreover, theycan completely lose bioactivity if exposed to significantchanges in pH, temperature, and/or ionic strength.Encapsulation in polymer multilayer microcapsulesbecomes a good solution to address both issues oftunable release76 and reliable protection.77 Itoh et al.have demonstrated capsule preparation via LbL assem-bly of chitosan and dextran sulphate followed by post-loading with FGF2 at pH 8, when the multilayer shells



have a relatively high permeability for the protein.78 Inanother report, TGF-b1 was post-loaded into heparin-containing polyelectrolyte multilayer capsules.79 Sheet al. exploited CaCO3 porous templates for loadingPARG/DS shells with FGF2 protected by heparin andBSA.77 FGF2-loaded capsules delivery to L929 cellsstimulated cell proliferation 10–30% more efficientlythan free FGF2. Capsules were also characterised by thehigh affinity to the cells’ surface (Fig. 5), which couldcreate a higher local concentration of FGF2, enablingmore effective utilisation of FGF2 by the cells.

The use of LbL-assembled capsules for delivery ofprotein-based vaccines and general aspects of interac-tions between capsules and the immune system havebeen extensively reviewed elsewhere.80 In vivo studies

pointed out that polymer multilayer capsules exhibiteddramatically lower levels of toxicity when compared totheir soluble constituents and were relatively welltolerated by mucosal tissue and cutis.80,81 Capsules wereefficiently internalised by antigen presenting cells andpromoted presentation of encapsulated model antigensby dendritic cells to T cells both in vitro and in vivo,opening perspectives for the delivery of clinicallyrelevant antigens.82–86

Proteins can be involved in specific recognition events,such as those occurring in avidin–biotin or antibody–antigen complexation, and play a major role in targetteddelivery of polymer multilayer microcapsules to cells.87–89

Antibodies can be attached to capsule surface throughadsorption,87,88 covalent bonding,89 or click chemistry.90

5 CLSM images of L929 cells incubated with FITC–BSA-loaded (Dex/PAr)3 microcapsules: a Cross-section fluorescence

image with z-axis fluorescence projection at the cross-plane displayed (windows at the bottom and on the right),

scale-bar: 20 mm. b Overlap of fluorescence mode and bright-field mode, scale-bar: 20 mm. c 3D fluorescence image

from the top view, frame length, and width: 210 mm; height: 13 mm77

4 Ratio of fluorescence intensities emitted by capsule interiors (Iint) and surrounding solution (Iext) 10 min after mixing

capsules and solutions of FITC–dextran of different molecular weights. a (tannic acid/poly(diallyl dimethyl ammonium

chloride)5 (TA/PDADMAC)5 capsules; the upper row shows confocal images of the capsules in dextran-77000 at differ-

ent pH. b tannic acid/poly(allyl amine hydrochloride)5 (TA/PAH)5 capsules; the upper row shows confocal images of

the capsules in dextran-2000000 at different pH67





The achievements in biofunctionalisation and devel-opment of stimuli-responsive controlled release mechan-isms open up an avenue for application of capsules inimmune-mediated cancer therapy. However, a recent invitro study discovered that the role of the antibody wasto enhance accumulation of capsules on the cell surfacerather than promote endocytosis.91 This observationmay provide evidence that other tools for capsuletargetting (e.g. navigation by magnetic field) have goodprospects for both in vivo and in vitro delivery ofanticancer drugs and therapeutics.92

Encapsulation of nucleic acidsDevelopments in gene therapy are targetting to treata large variety of inherited and chronic diseases,including cancer, AIDS, neurological disorders such asParkinson’s disease and Alzheimer’s disease, and cardi-ovascular disorders.93–95 Inside the living cells, nucleicacids are subjected to enzymatic cleaving and degrada-tion in acidic environment of endosomes and generallyneed extra protection on a way to their target, which isthe cell nucleus in case of DNA and cytoplasm in case ofRNA. Replication-deficient viral particles can pack andeffectively deliver genes but may be toxic and cause astrong immune response.96 Polymeric and liposomalparticles are also capable of cell transfection, but noneof the above mentioned compositions are as effective asthe viral delivery systems.97–101 Moreover, problems ofquality control and inherent pharmacological propertiesof some polymers (such as hypocholesterolemia inducedby chitosans) make some polymeric delivery systemsunfavourable for human use.102,103 Templated polymermultilayer capsules composed of polysaccharides andpolyaminoacids are known to be intercellularly degradableand less cytotoxic than corresponding free polymers.80,86,104

At the same time, they can offer much higher capacity formolecular cargo than liposomes. These features allow theconsideration of capsules as prospective gene deliveryvehicles.

Nucleic acids are natural polyanions and have beenused as multilayer film constituents since the LbLtechnique was introduced.105 Moreover, specific interac-tions such as DNA/spermidine binding were utilised toachieve LbL films and capsules.106,107 These assembliesare salt-responsive since a high concentration of saltdestroys the DNA/spermidine complex. NeutrAvidin–biotin interaction was also exploited to assemble capsulesof biotin-labelled DNA and NeutrAvidin.108 The Donathgroup was the first to report on successful delivery offunctional DNA into cells by polymer multilayer capsules,where plasmid DNA encoded for enhanced greenfluorescent protein and discosoma species red fluorescentprotein was incorporated within multilayer of dextransulphate and protamine.109 Transfection of Chinesehamster ovary cells (CHO-K1) by siRNA layers alternat-ing with those of PEI on the surface of gold nanoparticleswas observed by enhanced green fluorescent proteinexpression.110 Multilayer films can be composed ofoligonucleotides by hybridisation of complementaryblocks (for example, polyA–polyT, polyG–CT).111,112

Poly(4-styrene sulphonate)/poly(allyl amine hydro-chloride) multilayer films showed some permeabilitytowards DNA molecules of different lengths, asinvestigated by the molecular beacon approach.113

However, nucleic acids are quite vulnerable to themedium conditions and will degrade at temperature or

pH conditions associated with increased polymer multi-layer permeability. Therefore, the use of a standardpost-loading approach is considered to be problematic.Kreft et al. suggested a unique strategy to post-loaderythrocyte-templated capsules by drying them from asolution containing double-stranded DNA.114

Great advantages are seen by using CaCO3 templatesto achieve multiple cargo loading. Thus, by simulta-neous encapsulation of DNA and Pronase, controlledrelease of DNA was demonstrated.115 Mesoporoussilica microparticles modified with amino groups wereused to absorb oppositely charged molecules of short-length DNA and oligonucleotides. Layer-by-layermicrocapsules were then formed followed by disulphidecross-linking of shells and dissolution of the silicatemplate.116–118

Encapsulation of oils and poorly water solubledrugsSimilar to water soluble molecules, non-polar com-pounds can be pre- and post-loaded in polymer multi-layer capsules (Fig. 3). Post-loading of decane by fivestep solvent exchange was first demonstrated by Moyaet al.119 Later, a similar approach was used for encapsu-lation of doxorubicin and 5-fluorouracil solubilised inoleic acid by Sivakumar et al.120 and loading of amicrochamber array with sunflower oil by Kiryukhinet al.121 On one hand, a significant advantage of thepost-loading approach is the controlled size anddispersity of microparticles as these parameters arepre-determined by the solid templates used for capsuleformation. On the other hand, post-loading of oils inpolymer multilayer capsules is a material and timeconsuming process and often results in low encapsula-tion efficiency. Moreover, the shell must be physicallyrobust enough to withstand multiple solvent exchangesand a number of centrifugation cycles.

Layer-by-layer coating of primary stabilised oildroplets dispersed in the water phase appears to be astraightforward and versatile method to fabricate oil-loaded capsules. The McClement’s group pioneered oilencapsulation in two to three layered shells.122,123 LaterGrigoriev et al.124 were the first who reported onmultilayer shell assembly over oil microdroplets fol-lowed by Wackerbarth et al.125 and Szczepanowiczet al.126 Primary stabilisation of oil droplets is performedby placing a layer of ionic amphiphilic molecules at thewater/oil interface providing a core microparticle with acertain density of surface charge. Proteins,125,127,128

cationic124,129 and anionic123 lipids, and amphiphilicpolymers129 were used in fabrication of polymer multi-layer microcapsules templated on oil microdroplets.

Encapsulation in polymer multilayer shells improvesstability of oil microdroplets towards coalescence, andslows down the speed of both gravitational separation128

and lipid peroxidation. Elsewhere, Klinkesorn et al.proposed strong pro-oxidant effect of endogenoustransition metals naturally present in oils, surfactants,and/or water.123 Indeed, utilisation of the cation screen-ing effect of cationic emulsifiers or multilayer shellsterminated by a cationic layer affected the oxidativedegradation to some extent.130–132 A layer of tannic acid(TA), used as a metal scavenger, sandwiched betweentwo layers of poly(L-arginine) suppressed peroxidationalmost completely over 2 weeks of incubation at



37uC.127 Besides that, such a design of the capsule shellwould allow simultaneous delivery of oils and lowmolecular weight polyphenol compounds.

Encapsulation of anticancer drugsSeveral anticancer drugs are water soluble compoundswith low molecular weight; therefore additional mea-sures have to be used to retain them inside the polymermultilayer shells which are generally permeable forcompounds with a molecular weight smaller than5 kDa.133 Doxorubicin and/or daunorubicin were spon-taneously encapsulated by residual melamine formalde-hyde/PSS complex134 and multilayer capsules pre-loadedwith oppositely charged low molecular weight dextransulphate,135 PSS,136 carboxymethyl cellulose,137 orgelated BSA.138 In the last example, the pH-dependentcharge of BSA enabled pH-controlled release of theencapsulated drug. Doxorubicin hydrochloride wasconjugated to alkyne-functionalised poly(L-glutamicacid) via amide bond formation and as such used inLbL assembly of microcapsule via complexing withpoly(N-vinyl pyrrolidone) (PVP).139 Cyclodextrin–ada-mantane (CD–AD) host–guest interactions wereexploited by Luo et al. to introduce doxorubicin in theshell of polysaccharide-based microcapsules: the shellwas formed by alternate adsorption of carboxymethyldextran-graft-b-CD with AD modified doxorubicin.140

Andreeva et al. achieved shells, which retain doxorubi-cin hydrochloride using adsorption of polyamide on thesurface of calcium carbonate microparticles followed bythermal conversion of the polyamide layers into poly-imide coatings.141

Various approaches have been developed for LbLencapsulation of hydrophobic anticancer drugs. Doxo-rubicin and 5-fluorouracil were solubilised in oleic acid andloaded via solvent exchange method.120 Thierry et al.142

described an LbL assembly consisting of chitosan coupledto hyaluronic acid chemically modified by grafting pacli-taxel through a labile succinate ester linkage. In the samespirit, the Picart group reported on capsules composed ofchemically modified derivative of hyaluronic acid (alky-lamino hydrazide) containing hydrophobic nanocavitiessubsequently coupled with either PLL or quaternisedchitosan as polycations. Paclitaxel showed high affinity toalkylated hyaluronic acid and thus was entrapped byshells.58,143 Vodouhe et al. demonstrated that multilayerassemblies of unmodified PLL and hyaluronic acid canalso serve as drug reservoirs loaded with a finely tuneddose of paclitaxel.144 Paclitaxel nanoparticles prepared bya modified nanoprecipitation technique and LbL-coated

with PAH/PSS shells showed induced cell cycle arrest inthe G2/M phase after 24 and 48 h of incubation with ahuman breast carcinoma cell line, MCF-7.145

Cell viability studies comprehensively reviewed byYan et al. demonstrated enhanced cytotoxicity ofanticancer drugs delivered by LbL capsules in compar-ison to that induced by free drugs.21 Recent achieve-ments in targetted delivery of microcapsules91,92 revealtheir great potential to be used as delivery vehicles foranticancer drugs aiming to minimise damaging effect onnormal tissues while having an increased efficiency in theelimination of cancer cells.

Capsules as containers for chemical reactionsSize-selective permeability of polymer multilayer shellsopens up the opportunity to explore them as spatiallyconfined containers for chemical reactions.

Radtchenko et al. suggested in situ synthesis ofFe2O3 inside the polyelectrolyte multilayer shells madeof PSS/PAH.146 The actual method exploits the pHgradient across the shells created by a pre-encapsulatedpolybase. Thus, the pH inside the capsule appears to bemore alkaline than that outside. If such capsules areimmersed into a solution of iron salt, insoluble hydro-xide starts to precipitate exclusively within the capsuleinterior. For instance, the encapsulation of poly(allylamine) at a concentration of 0?1M induced a gradientof 1?8 pH units, sufficient enough to provide for theformation of Fe(OH)3 inside the capsule, while later onthe iron hydroxide restructured into Fe2O3. A slightlymodified routine involved incubation of the poly(allylamine)-loaded capsules in an Me(SO4)x (Me5Fe, Co,Zn, Mn) containing medium, which resulted in thesynthesis of magnetic ferrites and magnetite.12,147 Anotherexample is selective crystallisation of various dyesinside the PSS/PAH microcapsules achieved via step-wise changing of the physicochemical properties of themedia.148,149

Kreft et al.150 and Antipina et al.151 demonstrated theuse of microcapsules as spatially confined containers forresorufin formation catalysed by glucose oxidase (GOD)and horseradish peroxidase (POD). A schematic repre-sentation of the process for patterned capsules immobi-lised on a film is shown in Fig. 6. Loading of the enzymeswas performed by exploiting the pH-changeable perme-ability of PSS/PAH shells towards macromoleculeswhereas molecules of a substrate (b-D-glucose) and anelectron donor (Amplex Red) could freely diffuse throughthe shells. Once inside the capsules, the glucose moleculesoxidation is catalysed by GOD and H2O2 is formed.

6 Formation of resorufin in cavities of supported layer-by-layer (LbL)-assembled microcapsules151




Next, POD catalyses conversion of Amplex Red by H2O2

into the highly fluorescent resorufin, the process whichtakes place strictly within the interior of the patternedmicrocapsules.

Release from polyelectrolyte multilayercapsulesThe release of encapsulated cargo at a desired site andtime interval represents another important step in thedrug delivery process. Indeed, it is this functionality thatcontrols the dose and speed of drug delivery. As such,controlling the permeability of capsules’ shells to inducerelease is one of the key tasks in the area ofmicropackaging.152–154

As it can be seen from Fig. 7, chemical, physical andbiological release triggers are available.152 This chaptergives brief descriptions of a number of differentapproaches within each respective area. However, it isimportant to highlight, that LbL assemblies can besimultaneously modified with several groups of func-tional elements, thus possessing several options forcontrolled release of their content.

Chemical triggerspH

pH is a parameter which affects the permeability ofmultilayer capsules made of weak polyelectrolytes.Variation of the pH results in accumulation ofadditional charges (upon protonation of weak poly-bases or deprotonation of weak polyacids) inside themultilayer, and repulsion between these formed chargedgroups causes the capsules’ expansion, the formation ofpores in the shells and a resultant increase of theirpermeability. Up to some point, this process isreversible, but extremely high or low pH affects theintegrity of microcapsules that could trigger burstrelease of a payload.155 Poly(allyl amine hydrochlor-ide), poly(acrylic acid), and poly(methacrylic acid)(PMAA) are typical examples of weak polyelectrolytesactively used for fabrication of pH-responsive cap-sules.155 In addition, so-called ‘click-chemistry’ can beapplied to assemble capsules and therefore control theirpermeability.139

Extensive studies were conducted on polyelectrolytemultilayer capsules, whose shells were composed ofPAA/poly(vinyl alcohol) (PVA),156 chondroitin sul-phate/PLL,157 PAA/PVP or PMAA/PVP,158 and poly(-ethylenoxide) (PEO)/PVP.159 Burke et al. reported thepreparation of multilayered PLL/hyaluronic acid filmsshowing pH-responsive properties.160 It was alsoreported that the permeability of PAH/PMAA shellsswitched reversibly due to shrinking/swelling uponadjusting pH in the range between 2 and 11.155

In another report, the permeability of capsulesfabricated using PVP, poly(N-vinyl caprolactam) orpoly(N-isopropyl acrylamide) was monitored by thediffusion of FITC-labelled dextran and was shown tobe pH-dependant.161 pH is one of the parameters thatcan dramatically affect the thickness and swellabi-lity of polysaccharide-based multilayer films.162 pH-responsive shells can be assembled on cells and used toregulate their activities.163 pH-induced swelling andthe increase of the shells’ thickness were recentlyreported for silk ionomer capsules.164 Furtherimprovement of pH-dependant permeability controlcan be achieved by incorporating a cross-linker intothe shell of microcapsules.165 pH was also reported tobe the factor driving release from polymer stereo-complex capsules.166

Ionic strength and solvents

Increasing the ionic strength of an aqueous continuousphase where microcapsules are dispersed induces screen-ing of the electrostatic interactions between polyelec-trolytes within the multilayer. Therefore, this principlecan be applied to affect the capsules’ permeability andinitiate the release of a payload.153,167 This effect wasquantified by measuring the diffusion of dyes orfluorescently labelled polymers through the shells. Itwas found that the permeability coefficient has a strongnon-linear behaviour.

An interesting phenomenon can be observed if onepolymer in the polyelectrolyte pair possesses hydrophobicgroups as, for example, PSS. In this case, the high ionicstrength weakens the interaction between the chargedgroups, resulting in shrinkage of capsules. Gao et al.have recently reported encapsulation and release ofdextran by changing the permeability of PSS/poly(diallyldimethyl ammonium chloride) (PDADMAC) capsules.168

The salt-induced capsule fusion has been observed for(PDADMAC/PSS)4 capsules during evaporation of NaCl-containing solution. The phenomenon was explained bychanges in the polyelectrolytes conformation from rela-tively extended to coiled as the salt solution was gettingmore and more concentrated. Owing to the hydrophobicinteractions, the polyelectrolytes entangle, which preventstheir statistical distribution in a capsule membrane.Capsule fusion allows for the application of polymermultilayer capsules in intracellular delivery, gene transfec-tion and fabrication of artificial cells.169–170

Organic solvents also can be used for affecting thepermeability. Lvov et al. encapsulated urease into thePSS/PAH shells using a 1 : 1 ethanol/water mixture.171

In the ethanol/water continuous phase, capsules becameporous and their permeability towards urease increased.The solvent-induced pore formation was observed to bereversible, so that enzyme was retained by the membraneafter washing out of ethanol. Further research of theeffect of solvents on polyelectrolyte multilayer capsules

7 Schematic representation of release methods divided

according to their respective area. Reproduced from

Ref. 152 by permission of The Royal Society of

Chemistry




revealed that they can also be used for controlled releaseof hydrophobic actives.172 It can be noted that salt- andsolvent-responsive capsules can be applied in chemicalindustries, but their applicability in biological milieu israther limited.

Electrochemical and electrical triggersElectrical and electrochemical-responsive capsules havegood prospectives in micromechanical and biomedicalapplications.173 The effect of these stimuli on LbL shellpermeability is actively investigated.174,175 An appliedelectric field induces the influx of low molecular counter-ions and increases the osmotic pressure. Sensing isanother area where applicability of such stimuli isimpactful.176 Electrocatalysis was recently reported as apotential application area for LbL assemblies: all-metalmesoporous platinum/palladium films have been fabri-cated via LbL electrochemical deposition;177 in anotherapproach, alternating layers of gold nanoparticles andPAH were used in the build-up process of LbL shells.178

Physical triggersTemperature

The use of temperature to change the permeability ofLbL assemblies is one example of a physical trigger.Indeed, shrinking or swelling of LbL-assembled micro-capsules using thermal treatment was shown by Kohleret al.179

Subjected to elevated temperatures, multilayer filmsassembled on solid templates exhibit almost no changes inthickness.180 On the contrary, free multilayer filmsassembled at water/air interface shrink if heated in thepresence of water, pointing to the fact that water content isan important parameter in this process.181 Heat treatmentinduces significant changes in the permeability of hollowmultilayer shells as they are completely surrounded bywater.182 It was also reported that not only capsules, butalso block-co-polymers, micelles, nanogels, and core-shellnanoparticles are affected by such stimuli.

Enhanced mobility of polymers in multilayer shells isachieved upon an increase of the temperature above theglass transition temperature, Tg, of the polyelectrolytecomplex. At this point, the temperature increaseprovides enough energy to overcome the thresholdneeded for polymeric film rearrangement. First, thepolymers become mobile, and then either shrinking orexpansion takes place. The shrinking is accompanied bythe stiffening of the walls. It was shown that uponheating of (PDADMAC/PSS)4 microcapsules, reorgani-sation of the polyelectrolyte layers took place, leading toa denser structure.183 The shrinking, which is mostlyused for encapsulation, can be adjusted through theproper choice of polyelectrolyte multilayers. It should benoted that better understanding of polymer mobility andinterdiffusion is essential not only for the capsules build-up, but also for triggered release of a payload.184

Temperature is an important trigger for the encapsulationand release of biologically active molecules but it seldomfinds applications for intracellular and in vivo-controlledrelease of drugs since temperature is nearly constant atphysiological conditions. Therefore, remote triggers orstimuli based on external fields become relevant.185

Ultrasound

Ultrasonic waves have been used for a large numberof applications,186 including burst release from LbL

capsules upon their rupture by high power ultrasonicwaves.187 It was shown, for instance, that capsules withdenser, nanoparticle-enhanced shells were even moresensitive to ultrasound. The biggest challenge in thisarea is the necessity to reduce the intensity ofultrasound, eventually approaching the level allowed inmedicine. This low level rupturing was achieved forliposomes when adsorbed on the surface of larger LbLcapsules.188

Magnetic fields

One of the main applications of LbL shells withincorporated magnetic nanoparticles is targetted deliv-ery directed by external magnetic fields. The work ofLvov et al. has demonstrated that an alternatingmagnetic field also affects the permeability of shells ifthey contain aggregates of nanoparticles.189 Cobaltnanoparticles were incorporated into PSS/PAH multi-layer shells during the build-up process. Permeability ofthe shells to dextran molecules was negligible at thispoint, but increased substantially after applying alter-nating electromagnetic fields for 30 min at frequencies ofaround 100–300 Hz, thus initiating the release.

Release from magneto-responsive capsules made ofpolyelectrolytes, lipid layers and magnetic nanoparticleswas also demonstrated by Katagiri and coworkers.190 Inthat case, the release was attributed to a phase transitionof the lipid membrane caused by the localised heating ofFe3O4 nanoparticles under an alternating magnetic field.Simultaneous functionalisation of LbL shells by mag-netic and noble metal nanoparticles191 opens opportu-nities to use multiple triggers for release activation.

Mechanical deformation

Mechanical stress has been prevalently used for probingstiffness and mechanical properties of the LbL shells. Inthis area, several structural192 and mechanical193,194

characterisation techniques have been developed. Thenecessity to study mechanical stability of LbL shells waspushed by the challenges discovered upon applying themfor intracellular uptake,195 i.e. extensive deformability ofshells and losses of loaded molecules upon delivery.Stiffening of the shells can be achieved by incorporationof gold nanoparticles or carbon nanotubes.196 Hence, atfirst, the mechanical properties of LbL shells have beenstudied in order to improve their strength, but mechan-ical pressure or stimulus can be also used to trigger therelease.

Several regimes of mechanical deformations havebeen reported. It is possible to induce release by gentlypressing on an LbL shell, which subsequently recover itsshape once the pressure is released. This phenomenon isassociated with elastic (completely reversible) deforma-tion of the shells. Another type of release is achieved byplastic deformation: pressing and disrupting the shells,as shown schematically in Fig. 8a.

The best way to study the type of release was reportedby combining atomic force microscope with fluorescencemicroscope.197 Monitoring the encapsulated fluorescentmolecules permits one to visualise the release andmeasure the plastic deformation thresholds. For PSS/PDADMAC shells comprised of eight layers, the releasewas induced at levels above 18% of their relativedeformation (Fig. 8b). The plastic deformation of theshells was found to start at a relative deformation of20%. A recent study of the mechanical deformation of



LbL shells assembled on calcium carbonate templatesrevealed the complex nature of the polymeric matrixformed on these porous microparticles, but it was stillpossible to estimate the forces required for initiation ofthe release from the shells comprising a different numberof layers.198

Laser light

Laser light is another physical stimulus which permitsremote release of encapsulated materials.20 For biome-dical applications, the choice of wavelength is importantsince the light should be minimally absorbed by cells anda tissue. Lasers working in the near infra-red (NIR)region of the optical spectrum meet this requirement.199

Layer-by-layer shells with incorporated nanoparticles ofnoble metals were reported previously to be light-addressable,200,201 the cause of their rupture wasexplained by the localised heating of nanoparticlesirradiated within their absorption bands. The controlover concentration can be made by controlling patchi-ness of microcapsules202 while control over concentra-tion and aggregation state of nanoparticles in the shellscan be made by polymers or adsorption conditions.203

On one hand, these steps allow for enhancement of theabsorption in the NIR region, making LbL shellssensitive to this light. While on the other hand, theypermit localisation of heat and minimisation of potentialside effects. Release from polymer multilayer capsulesupon laser irradiation has been the subject of severalreports.204,205 In addition to inducing release, laser lighthas been also used for encapsulation.206 The encapsula-tion was attributed to rearrangements of the polymersand changes in the permeability of LbL shells followingthe exposure to light. The effectiveness of opticalencapsulation was shown to increase with increasingirradiation time.207

Some more advanced forms of release includecontrollable release,208 which has been demonstratedfor polyelectrolyte multilayer capsules. Upon stoppingthe irradiation, the heat is no longer generated and thepolymeric multilayer returns to the so-called ‘glassy’ (orimmobile) state and become impermeable. Wavelength-selective release has been also shown with the incorpora-tion of metal nanorods in the multilayer shells.209

Erokhina et al. used bacteriorhodopsin incorporated inLbL shells as a light harvesting protein to initiate protonpumping.210 Upon exposure to light, a drop in pHincreases the shells permeability due to the formation ofpores and initiates the release of an encapsulatedfluorescent dye. Other interesting method of light-induced release from LbL shells uses an approach oncedeveloped for photodynamic therapy.211

Intracellular delivery has always been recognised as animportant application area for polymer multilayercapsules.212 Cells can uptake capsules by spontaneousphagocytosis or by electroporation which was shown towork even for micron-sized capsules. Thermally shrunkLbL shells were shown to be strong enough to withstandthe pressure of cells upon incorporation. Palankar et al.investigated antigen presentation on major histocompat-ibility complex (MHC) class I molecules.213 Multilayercapsules loaded with peptides were incorporated by theVero and CHO cells followed by their controlledrupturing with a NIR laser pulse and release of peptidesdirectly inside the cells. Cells were then stained with themonoclonal antibody Y3, which binds to the peptide–protein complex (H-2Kb). To the best of our knowledge,the above experiments are the first evidence of con-trollable intracellular release, and they have alreadybeen very useful for monitoring the immune systemresponse.

Remote release of encapsulated materials with NIRlaser light was recently reported in neurons.214 Thelocalised heating of the LbL shells containing a lowamount of nanoparticles incorporated into the LbLshells is highly localised and was confirmed to notadversely affect the cells viability.

Enzymes as release triggersBiological stimuli represent very attractive means ofreleasing encapsulated materials. In such cases, therelease is controlled by enzymes.215 Release of oligonu-cleotide sequences has been demonstrated from micro-capsules assembled by the polycation-free method.116 Asignificant advantage of such a method includes highretention of encapsulated molecules, while disadvan-tages are associated with difficulties in molecules

8 a Push force-curve on a typical capsule. Simple schematics of the capsule before contact with the colloidal probe and

at maximum deformation are shown. b Average fluorescence intensity from a typical microcapsule subjected to

mechanical deformation (filled circles) and a control microcapsule not subjected to mechanical deformation (open cir-

cles) calculated from images taken after each push–pull cycle as a function of total capsule deformation. The dashed–

dotted line indicates the threshold total deformation (18%) beyond which release is triggered. Reproduced from Ref.

197 by permission of The Royal Society of Chemistry




delivery. In 2006, De Geest et al. demonstratedenzymatic degradation of LbL shells made of poly(L-arginine) as the polycation and dextran sulphate as thepolyanion.104 It was reported that such shells made ofbiomacromolecules with encapsulated polyamino acidwere subjected to intracellular degradation, while theshells made of synthetic polyelectrolytes (PSS/PAH)remained intact. The degradation was demonstratedusing Pronase, a mixture of proteases that cleavesproteins and peptides non-specifically.

Currently, research is under way to investigate theinfluence of novel molecules and enzymes216 and toachieve control over the release rate217,218 varying thethickness of multilayer shell and/or concentration ofpronase, e.g. to govern the release rate of non-pronasedependent biologically important compounds such asDNA.115 Specific degradation of collagen-containingmultilayer capsules was demonstrated by metalloprotei-nases (MMP enzymes). Monitoring of capsule degrada-tion was facilitated in situ by X-ray fluorescence fromcapsules containing gold nanoparticles.219 Degradationof microcapsules was monitored using UV–Vis spectro-scopy as demonstrated by Orozco et al.220 Itoh et al.constructed dextran sulphate/chitosan microcapsulesresponsive to chitosanase.221 A potential disadvantageof these capsules is that chitosanase is not present inmammalian cells. Biomarkers have also been used toinduce release from polymer multilayer capsules.222 Therelease of labelled transferrin from disulphide cross-linked polymer capsules made of PVP and PMAAfunctionalised with cysteamine was demonstrated byCaruso and coworkers by the addition of dithiothreitol(DTT).223 Such an approach has a potential for a varietyof diverse applications in vivo.

The biggest advantage of enzyme-degradable capsulesin living systems is that no external trigger is required fortheir opening.224 Thus biodegradable microcapsules are

expected to have a great influence on drug delivery invivo and in vitro.

Microchamber arraysSite-specific release of chemical compounds in small andprecisely defined quantities is another challenge in thedevelopment of delivery systems. So far, the mostcommon approach exploits microelectromechanical sys-tems (MEMS) such as micro-pumps, valves or electro-chemically dissolving caps which electronically triggerthe release of a desired component from an array ofmicro-reservoirs.225–228 Such systems provide precisetemporal and spatial control over the release process;however, they require external components like a powersupply and a piping. The size scale of MEMS is usuallyon the order of tens of microns and above. RecentlyKiryukhin et al. have reported the method to fabricate apatterned array of standing, hollow microchambersmade of trigger-responsive polyelectrolyte multilayerfilms,121,229,230 a schematic of the process is shown inFig. 9.

First, an array of micro-wells of pre-determined size,shape and arrangement is fabricated on a sacrificialtemplate. Second, a PEM film is deposited via LbLassembly of oppositely charged polyelectrolytes. At thispoint, the coated microwells could be filled with a cargoof choice by a number of the techniques developed forsolid particles or liquids.121,230–232 Proper sealing of theloaded microwells on a support is crucial for effectivestoring of the cargo and preventing leakage. This can beachieved upon the pressure-induced adhesion towards asupport pre-coated with another multilayer film.233

Mechanical pulling-out or dissolving of the sacrificialtemplate leaves a patterned array of standing micro-chambers loaded with the cargo. Alternatively, an arrayof hollow microchambers could be fabricated first andthen post-loaded with a cargo.121,230 Remote rupture of

9 Schematic illustration of PEM microchambers fabrication, their loading with cargo species and site-specific release-on-

demand230




selected chambers enables programmed release-on-demand of the cargo and could be utilised in a varietyof applications, such as the delivery of drugs, the releaseof bioactive cocktails for biochemical studies on a singlecell level, etc. It can be achieved using focussed laserradiation at a wavelength within the plasmon absorptionband of gold nanoparticles, which were incorporated inthe chamber shell upon LbL assembly.230

Below the authors consider each of the steps leadingto the patterned PEM microcompartments in moredetails.

LbL assembly of the PEMs in confinedgeometriesEven deposition of polyelectrolytes both on the outersurface of a sacrificial template and on the inner surfaceof imprinted microwells is crucial for successful fabrica-tion of the microchambers. The following factors cancause detrimental non-uniformity of the film thickness.

A thinner PEM film is formed inside the wells if:(i) there is poor wetting of these wells with

polyelectrolyte solutions(ii) the size of the wells is smaller than the

dimensions of polyelectrolyte coils and thephysical exclusion of polyelectrolytes occurs

(iii) there is a depletion of polyelectrolyte concentra-tion across the wells from the surface to thebottom due to electrostatic interaction betweenpolyelectrolyte coils and charged surfaces con-fining the wells, or due to slow diffusion of coilsinto the wells.

On the contrary, a thicker PEM film is formed inside thewells if:

(i) non-adsorbed polyelectrolytes are incompletelydrained out of the wells during the washing steps.

In practice, special precautions should be made to avoidair bubbles from being trapped inside the wells, e.g. byapplying the ultrasound prior to LbL assembly. Usingpolyelectrolyte solutions of high ionic strength helps toovercome the surface charge-induced depletion of PEconcentration due to electrostatic screening. Also thetime of the polyelectrolyte adsorption step as well as thetime and number of the washing steps should be chosenproperly.

Loading the PEM-coated wells with a cargoA cargo, e.g. microparticles, could be introduced intothe PEM-coated wells exploiting the template-assisted

self-assembly of colloids developed by Xia et al.232 Asthe rear front of an aqueous dispersion of colloidparticles moves slowly in a 50 mm-thick layer confinedbetween the substrate with an array of wells and theglass above, the capillary forces drag colloid particlesacross the surface until they are physically trapped bythe wells. Figure 10 shows SEM images of MF colloidalparticles entrapped in the microwells of differentgeometries pre-coated with PAH/PSS multilayer film.The maximal number of particles in a well depends onthe ratio of its dimensions to the diameter of theparticles.

This approach can be very versatile once porousparticles with the adsorbed molecules of interest areapplied. If the number of such particles housed in onechamber is large enough (Dwell&Dparticle), one cancontrol the ratio between different components in achamber by simply mixing several types of particles eachcarrying one component. Thus, specific biochemicalcocktails or enzymatic mixtures for cascade reactionscan be achieved.

Sealing and transfer of microchambers arrayConventional adhesives unfortunately require organicsolvents and/or thermal treatments, which might beharmful for delicate cargo. In addition, it is typicallydifficult to apply a uniform nanometre thick adhesivethat will seal the microwells without penetrating inside.One way is to coat a support with adhesive PSS–PDADMAC multilayer film and press it towards aPAH/PSS-coated template having colloidal particlesentrapped in the microwells. Applied pressure inducesadhesion between both multilayers with the tensile bondstrength as high as 3?5 MPa.233 A much weaker tensilebond strength of 0?35 MPa between PAH–PSS multi-layer and the template (PMMA) ensures adhesive breakat this interface and allows an easy pulling off of thePMMA template that leaves behind a patterned array ofstanding microchambers sealed towards a support, asshown in Fig. 11.

This method has several advantages if compared tothe conventional dissolving of a template: it does notrequire organic solvents; the imprinted templateremains undamaged and can be recycled for fabricationof further samples thus making the process of free-standing microchamber arrays fabrication sustainablewith reduced efforts.

10 SEM images of MF particles trapped in the poly(4-styrene sulphonate)–poly(allyl amine hydrochloride)40 (PSS–PAH)40-

coated wells of different patterns. Mean size of MF particles was 2?20 a and 4?88 mm b. Scale bars of SEM images

are 10 mm230




The condition to retain structural shape of thestanding chambers puts additional requirements on themechanical properties of PEM shells. It was found thatchambers demonstrate ground collapse with their roofscontacting the underlying support or lateral collapse(for chambers with high aspect ratio) if made of shellsthat are thinner than a certain critical value (seeFig. 12).121,229 On the contrary, stable and standingchambers are formed if thicker shells are used.

The critical thickness of a cylindrical shell could beestimated using Euler’s model of critical stress todescribe collapse of chambers and assuming adhesivecontact of chamber’s roof with a support as the majormechanism responsible for collapse:121

h2cr~

a2sad

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi3(1{u2)

p

2E,

where a is the radius of a cylinder, sad is the adhesionstrength of a PEM shell to a support, v is the Poisson’sratio, and E is Young’s modulus of the shell. Themodulus of water-immersed PAH–PSS multilayer films

is in the range of y500–750 MPa as measured indepen-dently by osmotic technique234 and stress-inducedmechanical buckling instabilities.235 It was found to beindependent of the film thickness over a wide range from10 to 200 nm. The modulus of PDADMAC–PSS multi-layer is y100 MPa, as measured by AFM.194 Using theseparameters, the critical thicknesses were estimated to bey300 andy1000 nm for cylindrical PAH–PSS chambershaving 7 and 25 mm in diameter, and y740 nm for 7 mmchambers of softer PDADMAC–PSS, all in goodagreement with experiment.121,229

Thus, by varying the templates, one can fabricatestanding arrays of mechanically stable hollow/loadedmicrochambers with different sizes, shapes and patternssealed towards a support; some are shown in Figs. 12and 13.

Post-loading the hollow microchambers throughthe shellsAlternatively, an array of hollow microchambers couldbe fabricated first and then post-loaded with a cargo, e.g.

11 SEM images of surfaces after the adhesive tensile break: poly(4-styrene sulphonate)–poly(allyl amine hydrochloride)40

(PSS–PAH)40 film with array of microchambers loaded with 2?20 mm MF particles remains sealed towards a poly(4-

styrene sulphonate)-poly(diallyl dimethyl ammonium chloride)8 (PSS–PDADMAC)8-coated silicon wafer (a), while

PMMA substrate with array of microwells is pulling out (b). Inset shows the cross-sections of corresponding micro-

chambers. All scale bars: 10 mm230,233

12 SEM images of microchambers of different geometries made of poly(allyl amine hydrochloride)–poly(4-styrene sulpho-

nate) (PAH–PSS) a–d, g, h and poly(diallyl dimethyl ammonium chloride)–poly(4-styrene sulphonate) (PDADMAC–PSS)

e, f multilayers. Thickness of the PEM film is y200 a, g, 300 h, 400 b, c, e, 750 d, and 550 nm f. All scale bars:

10 mm121,229





by the solvent-exchange method. The method was devel-oped to load water-dispersed PEM capsules with oils usingan intermediate solvent such as ethanol or acetonecompatible with both water and oil phases.119 There is noneed for water-miscible solvents as in this case micro-chambers are first formed after the template dissolutionand are already filled with toluene. As an examplesunflower oil can be directly applied over the toluene-filledPEM chambers for 1 hour. Then excess oil is washed outwith toluene and the sample is allowed to dry. CompositeConfocal Raman Microscopy images containing informa-tion from both oil (red) and PEM (green) bandsdemonstrate that oil droplets are specifically located insidethe PEM chambers and completely fill them (Fig. 14a,b).121

The method can be easily modified to load chamberswith oil-soluble staff like a perylene derivative whichdisplays green fluorescence.230 Corresponding fluorescentmicroscope images are shown in Fig. 14c. Thus, diffusionof the dye molecules was not hindered by the micro-chambers’ shells which are much thicker compared toPEM capsules. Post-loading of the microchambers couldbe extended to a variety of different cargo, exploitingtunable permeability of PEM films by a number oftriggers, e.g. pH, ionic strength, redox potential etc.19

However, the feasibility of the techniques developed forPEM capsules should be verified each time.

Light-triggered release of a cargo from selectedmicrochambersRemote rupture of individual chambers was achievedusing focussed laser radiation.230 Incorporation of metal

nanoparticles in a PEM shell makes it sensitive towardsirradiation within the plasmon absorption band of thesenanoparticles. The energy of absorbed light dissipates asheat, resulting in a highly localised temperature increasethat destroys the surrounding y400 nm thick PEM filmin the same way as it was shown previously for few nmthick PEM capsules.202,236,237 Entrapped MF particleswere released from selected chambers by focussed532 nm light, the second harmonic of a pulsed Nd-YAG laser (see Fig. 15). The microchambers are filledwith water as particles undergo Brownian motion insidethe chambers without leaving it. Once the selectedchamber is affected with a laser pulse, the multilayer capbursts followed by the release of the previously accom-modated particles. Meanwhile, neighbouring chambersremain undamaged.

ConclusionOver the past two decades, intensive studies on the LbLassembly have allowed many challenges in surfacemodification and fabrication of functional thin films tobe overcome. Layer-by-layer assembly on templates ofdifferent geometries have enabled a novel class ofmicropackaging containers made of functional multi-layer shells, referred here as capsules and chambers.Employed as delivery systems, these containers reveal aunique opportunity to combine multiple functionalitiesin one entity. For instance, one capsule can achieveseveral objectives, such as protection, targetted delivery,triggered and site specific release. Physical and chemicalproperties of polymers involved in the assembly as well

13 SEM images of microchambers of different geometries and patterns made of poly(allyl amine hydrochloride)–poly(4-

styrene sulphonate) (PAH–PSS) multilayers. Thickness of the PEM film is y750 a and 400 b nm

14 Confocal Raman microscope images of chambers filled with oil: top view a and cross-section b. Colour code of the

image: red5oil (1660 cm21 band is assigned to double bond, C5C stretching); green5PEM (1604 cm21 band is

assigned to C–C stretching in the aromatic ring of PSS). All scale bars: 5 mm.121 Fluorescent microscope image of

chambers loaded with an oil-based solution of 3,4,9,10-tetra-(hectoxy-carbonyl)-perylene c230





as the shell thickness pre-define the permeability of thecontainers. Making the LbL assemblies of pH-, sugar-or enzyme-responsive polymers allows for the con-trolled, triggered release of a payload under the influenceof the corresponding chemical or biological stimuli.Capsules responsive to remote physical triggers, such aslight, ultrasound or magnetic field, are prospectivecandidates for targetted delivery in a wide range ofapplications. Indeed, an opportunity to remotely changethe (bio)-chemical composition in spatially confinedspecific areas and at a specific time is impactful forcatalysis, biotechnology, and cell and tissue engineering.

In this review, the authors described the fabrication,loading and controlled delivery and release options fortwo different LbL engineered micropackaging systemswith regard to geometry of used templates. Capsulesformed on a surface of sacrificial colloidal organic orinorganic microparticles have been well known forabout 15 years. A relatively new micropackaging systemis a microchamber array formed on the imprintedsurfaces of sacrificial templates, as first published byKiryukhin et al in 2011. Apparently, a microchamberarray may be considered as a regular 2D version of asuspension of capsules. Resent advances in nanolitho-graphy such as roll-to-roll imprinting together withautomated LbL deposition open up a possibility to scaleup the fabrication of microchamber arrays. The array ofpolymer multilayer microchambers is a unique systemwith regard to time and site specific release of a preciselycontrolled amount of a payload, which can be especiallyadvantageous for ‘static’ applications, such as implantcoatings and bioscaffolds.

Layer-by-layer encapsulation of large molecules hasbeen well developed. However, a lot of interestingapplications are anticipated in areas requiring deliveryof small water soluble molecules. Microchamber arrayswill possibly offer some advantages with regard to thecapture of low molecular weight compounds, as theirfabrication process can involve hydrophobic polymersand organic solvents. Loading of microchambers with acargo seems to be rather straightforward and might facefewer obstacles due to the relative ease of handling themacroscopic surfaces.

Having both micropackaging systems at hand, thechoice now is mainly pre-determined by the applicationrequirements. Capsules have no viable alternative where3D delivery is needed, but they could not compete withmicrochamber arrays in the case of surface-mediateddelivery. In the coming years the authors anticipateactive development of encapsulation strategies for bothtypes of systems with high attention paid to the delivery

of small water soluble molecular cargo includingvolatiles and fragrances.238

Current research activities on LbL assemblies aremainly directed towards intracellular delivery and in vivoapplications. So far, the most successful application ofLbL capsules in vivo is the delivery of model vaccines,81–86

where degradation of the capsule and mild inflammationresponse was documented. Further exciting developmentsare foreseen in emerging areas of biosensors andtheranostics.239

The authors suppose that applicable areas for LbL-assembled micropackaging systems will broaden in thenear future and also involve personal care and functionalfood products. The outstanding versatility of LbL films interms of geometry, integrity and payload will certainlykeep attracting the attention of researchers from variousfields and result in many fascinating developments.

Acknowledgements

Authors express their sincere thanks to Professor K.Elizabeth Tanner (University of Glasgow) and Dr. E. L.Williams (Institute of Materials Research andEngineering, A*STAR, Singapore) for critically readingthe manuscript and making valuable comments. AndreG. Skirtach thanks FWO for support. Please checkwhether the edits made to the ‘Acknowledgment’ sectionare fine.

References1. R. Langer, D. A. Tirrell: ‘Designing materials for biology and

medicine’, Nature, 2004, 428, 487–492.

2. V. P. Torchilin: ‘Recent advances with liposomes as pharmaceu-

tical carriers’, Nat. Rev. Drug Discov., 2005, 4, (2), 145–160.

3. C. J. Hawker, K. L. Wooley: ‘The convergence of synthetic

organic and polymer chemistries’, Science, 2005, 309, 1200–1205.

4. G. Decher: ‘Fuzzy nanoassemblies: toward layered polymeric

multicomposites’, Science, 1997, 227, 1232–1237.

5. Y. Lvov, G. Decher, H. Mohwald: ‘Assembly, structural

characterization and thermal behavior of layer-by-layer deposited

ultrathin films of polyvinylsulfonate and polyallylamine’,

Langmuir, 1993, 9, 481–486.

6. Y. Lvov, K. Ariga, I. Ichinose, T. Kunitake: ‘Assembly of

multicomponent protein films by means of electrostatic layer-by-

layer adsorption’, J. Am. Chem. Soc., 1995, 117, 6117–6122.

7. G. B. Sukhorukov, E. Donath, S. Davis, H. Lichtenfeld,

F. Caruso, V. I. Popov, H. Moehwald: ‘Stepwise polyelectrolyte

assembly on particle surfaces: a novel approach to colloid design’,

Polym. Adv. Technol., 1998, 9, 759–767.

8. E. Donath, G. B. Sukhorukov, F. Caruso, S. A. Davis,

H. Moehwald: ‘Novel hollow polymer shells by colloid-templated

assembly of polyelectrolytes’, Angew. Chem. Int. Ed., 1998, 37,

(16), 2202–2205.

9. N. Shah, J. Hong, M. Hyder, P. Hammond: ‘Osteophilic

multilayer coatings for accelerated bone tissue growth’, Adv.

Mater., 2012, 24, 1445–1450.

15 Optical microscope images showing release of MF particles into water by opening a specific chamber with focussed

laser radiation230




http://www.maneyonline.com/action/showLinks?crossref=10.1002%2F%28SICI%291521-3773%2819980904%2937%3A16%3C2201%3A%3AAID-ANIE2201%3E3.0.CO%3B2-E&isi=000075860500005

http://www.maneyonline.com/action/showLinks?crossref=10.1038%2Fnature02388&isi=000220540100031

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fla00026a020

http://www.maneyonline.com/action/showLinks?crossref=10.1002%2Fadma.201104475&isi=000301336500011

http://www.maneyonline.com/action/showLinks?crossref=10.1038%2Fnrd1632&isi=000226721500020

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fja00127a026&isi=A1995RC45000026

http://www.maneyonline.com/action/showLinks?crossref=10.1126%2Fscience.1109778&isi=000231395400034

http://www.maneyonline.com/action/showLinks?crossref=10.1002%2F%28SICI%291099-1581%281998100%299%3A10%2F11%3C759%3A%3AAID-PAT846%3E3.0.CO%3B2-Q&isi=000076733900025

http://www.maneyonline.com/action/showLinks?crossref=10.1126%2Fscience.277.5330.1232

10. Y. Lvov, G. Decher, G. Sukhorukov: ‘Assembly of thin films by

means of successive deposition of alternate layers of DNA and

poly(allylamine)’, Macromolecules, 1993, 26, 5396–5399.

11. M. Ferreira, J. H. Cheung, M. F. Rubner: ‘Molecular self-

assembly of conjugated polyions: a new process for fabricating

multilayer thin film heterostructures’, Thin Solid Films, 1994, 244,

806–809.

12. D. G. Shchukin, I. L. Radtchenko, G. B. Sukhorukov: ‘Micron-

scale hollow polyelectrolyte capsules with nanosized magnetic

Fe3O4 inside’, Mater. Lett., 2003, 57, 1743–1747.

13. D. G. Shchukin, G. B. Sukhorukov: ‘Nanoparticle synthesis in

engineered organic nanoscale reactors’, Adv. Mater., 2004, 16, (8),

671–682.

14. W. Meier: ‘Polymer nanocapsules’, Chem. Soc. Rev., 2000, 29,

295–303.

15. S. Forster, M. Konrad: ‘From self-organizing polymers to nano-

and biomaterials’, J. Mat.Chem., 2003, 13, 2671–2688.

16. A. Antipov, G. B. Sukhorukov: ‘Polyelectrolyte multilayer

capsules as vehicles with tunable permeability’, Adv. Colloid

Interface Sci., 2004, 111, 49–61.

17. H. Ai, S. A. Jones, M. M. de Villiers, Y. M. Lvov: ‘Nano-

encapsulation of furosemide microcrystals for controlled drug

release’, J. Control. Release, 2003, 86, (1), 59–68.

18. O. Kreft, A. Javier Munoz, G. B. Sukhorukov, W. J. Parak:

‘Polymer microcapsules as mobile local pH-sensors’, J. Mater.

Chem., 2007, 42, 4471–4476.

19. L. J. De Cock, S. De Koker, B. G. De Geest, J. Grooten,

C. Vervaet, J. P. Remon, G. B. Sukhorukov, M. N. Antipina:

‘Polymeric multilayer capsules in drug delivery’, Angew. Chem.

Int. Ed., 2010, 49, (39), 6954–6973.

20. M. N. Antipina, G. B. Sukhorukov: ‘Remote control over

guidance and release properties of composite polyelectrolyte

based capsules’, Adv. Drug Deliv. Rev., 2011, 63, (9), 716–729.

21. Y. Yan, G. K. Such, A. P. R. Johnston, H. Lomas, F. Caruso:

‘Toward therapeutic delivery with layer-by-layer engineered

particles’, ACS Nano, 2011, 5, (6), 4252–4257.

22. I. Erel-Unal, S. Sukhishvili: ‘Hydrogen-bonded multilayers of a

neutral polymer and a polyphenol’, Macromolecules, 2008, 41,

(11), 3962–3970.

23. Z. P. Wang, Z. Q. Feng, C. Y. Gao: ‘Stepwise assembly of the

same polyelectrolytes using host–guest interaction to obtain

microcapsules with multiresponsive properties’, Chem. Mater.,

2008, 20, (13), 4194–4199.

24. A. A. Antipov, G. B. Sukhorukov, S. Leporatti, I. L. Radtchenko,

E. Donath, H. Moehwald: ‘Polyelectrolyte multilayer capsule

permeability control’, Colloids Surf., A, 2002, 198, 535–541.

25. G. Ibarz, L. Daehne, E. Donath, H. Moehwald: ‘Smart micro and

nanocontainers for storage, transport, and release’, Adv. Mater.,

2001, 13, (17), 1324–1327.

26. K. Koehler, G. B. Sukhorukov: ‘Heat treatment of polyelectrolyte

multilayer capsules: a versatile method for encapsulation’, Adv.

Funct. Mater., 2007, 17, (13), 2053–2061.

27. Y. Lvov, A. Antipov, A. Mamedov, H. Moehwald, G. B.

Sukhorukov: ‘Urease encapsulation in nanoorganized micro-

shells’, Nano Lett., 2001, 1, (3), 125–128.

28. B. Li, D. T. Haynie: ‘Multilayer biomimetics: reversible covalent

stabilization of a nanostructured biofilm’, Biomacromolecules,

2004, 5, (5), 1667–1670.

29. D. T. Haynie, N. Palath, Y. Liu, B. Y. Li, N. Pargaonkar:

‘Biomimetic nanostructured materials: inherent reversible stabili-

zation of polypeptide microcapsules’, Langmuir, 2005, 21, (3),

1136–1138.

30. Y. J. Ma, W. F. Dong, M. A. Hempenius, H. Moehwald, G. J.

Vancso: ‘Redox-controlled molecular permeability of composite-

wall microcapsules’, Nat. Mater., 2006, 5, (9), 724–729.

31. B. G. De Geest, A. M. Jonas, J. Demeester, S. C. De Smedt:

‘Glucose-responsive polyelectrolyte capsules’, Langmuir, 2006, 22,

(11), 5070–5074.

32. T. Levy, C. Dejugnat, G. B. Sukhorukov: ‘Polymer microcapsules

with carbohydrate sensitive properties’, Adv. Funct. Mater., 2008,

18, (10), 1586–1594.

33. L. Hartmann, M. Bedard, H. G. Boerner, H. Moehwald, G. B.

Sukhorukov, M. Antonietti: ‘CO2-switchable oligoamine patches

based on amino acids and their use to build polyelectrolyte

containers with intelligent gating’, Soft Matter, 2008, 3, 534–539.

34. Q. H. Zhao, B. S. Han, Z. H. Wang, C. Y. Gao, C. H Peng, J. C.

Shen: ‘Hollow chitosan–alginate multilayer microcapsules as drug

delivery vehicle: doxorubicin loading and in vitro and in vivo

studies’, Nanomed. Nanotech. Biol. Med., 2007, 3, (1), 63–74.

35. O. P. Tiourina, A. A. Antipov, G. B. Sukhorukov, N. L.

Larionova, Y. Lvov, H. Moehwald. ‘Entrapment of alpha-

chymotrypsin into hollow polyelectrolyte microcapsules’,

Macromol. Biosci., 2001, 1, (5), 209–214.

36. S. Q. Ye, C. Y. Wang, X. X. Liu, Z. Tong, B. Ren, F. Zeng: ‘New

loading process and release properties of insulin from poly-

saccharide microcapsules fabricated through layer-by-layer

assembly’, J. Controlled Release, 2006, 112, (1), 79–87.

37. S. R. Nayak, M. J. McShane: ‘Fluorescence glucose monitoring

based on transduction of enzymatically-driven pH changes within

microcapsules’, Sensor Lett., 2006, 4, (4), 433–439.

38. S. Q. Ye, C. Y. Wang, X. X. Liu, Z. Tong: ‘Multilayer

nanocapsules of polysaccharide chitosan and alginate through

layer-by-layer assembly directly on PS nanoparticles for release’,

J. Biomater. Sci. Polym. Ed., 2005, 16, (7), 909–923.

39. D. B. Shenoy, G. B. Sukhorukov: ‘Microgel-based engineered

nanostructures and their applicability with template-directed

layer-by-layer polyelectrolyte assembly in protein encapsulation’,

Macromol. Biosci., 2005, 5, (5), 451–458.

40. R. Srivastava, M. J. McShane: ‘Application of self-assembled

ultra-thin film coatings to stabilize macromolecule encapsulation

in alginate microspheres’, J. Microencapsulation, 2005, 22, (4),

397–411.

41. B. G. De Geest, C. Dejugnat, M. Prevot, G. B. Sukhorukov,

J. Demeester, S. C. De Smedt: ‘Self-rupturing and hollow

microcapsules prepared from bio-polyelectrolyte-coated micro-

gels’, Adv. Funct. Mater., 2007, 17, (4), 531–537.

42. G. B. Sukhorukov, D. V. Volodkin, A. Guenther, A. I. Petrov,

D. B. Shenoy, H. Moehwald: ‘Porous calcium carbonate

microparticles as templates for encapsulation of bioactive

compounds’, J. Mater. Chem., 2004, 14, (14), 2073–2081.

43. A. I. Petrov, D. V. Volodkin, G. B. Sukhorukov: ‘Protein-calcium

carbonate coprecipitation: a tool for protein encapsulation’,

Biotechnol. Prog., 2005, 21, (3), 918–925.

44. D. V. Volodkin, N. I. Larionova, G. B. Sukhorukov: ‘Protein

encapsulation via porous CaCO3 microparticles templating’,

Biomacromolecules, 2004, 5, (5), 1962–1972.

45. D. V. Volodkin, A. I. Petrov, M. Prevot, G. B. Sukhorukov:

‘Matrix polyelectrolyte microcapsules: new system for macro-

molecule encapsulation’, Langmuir, 2004, 20, (8), 3398–3406.

46. A. Yashchenok, B. Parakhonskiy, S. Donatan, D. Kohler,

A. Skirtach, H. Moehwald: ‘Polyelectrolyte multilayer micro-

capsules templated on spherical, elliptical and square calcium

carbonate particles’, J. Mater. Chem. B, 2013, 1, (9), 1223–1228.

47. Y. X. Liu, J. Yang, Z. Q. Zhao, J. J. Li, R. Zhang, F. L. Yao:

‘Formation and characterization of natural polysaccharide hollow

nanocapsules via template layer-by-layer self-assembly’, J. Colloid

Interface Sci., 2012, 379, 130–140.

48. H. Li, J. Jiang, Y. S. Ge, J. L. Xu, P. Y. Zhang, W. Zhong, S. Y.

Chen: ‘Layer-by-layer hyaluronic acid–chitosan coating promoted

new collagen ingrowth into a poly(ethylene terephthalate) artificial

ligament in a rabbit medical collateral ligament (MCL) reconstruc-

tion model’, J. Biomater. Sci. Polym. Ed., 2013, 24, (4), 431–446.

49. L. M. He, Y. F. Shi, Q. Han, Q. H. Zuo, S. Ramakrishna,

W. Xue, L. B. Zhou: ‘Surface modification of electrospun

nanofibrous scaffolds via polysaccharide-protein assembly multi-

layer for neurite outgrowth’, J. Mater. Chem., 2012, 22, (26),

13187–13196.

50. Y. Luo, S. G. Wang, M. W. Shen, R. L. Qi, Y. Fang, R. Guo,

H. D. Cai, X. Y. Cao, H. Tomas, M. F. Zhu, X. Y Shi.: ‘Carbon

nanotube-incorporated multilayered cellulose acetate nanofibers

for tissue engineering applications’, Carbohydr. Polym., 2013, 91,

(1), 419–427.

51. L. Y. Huang, M. C. Yang: ‘Hemocompatibility of layer-by-layer

hyaluronic acid/heparin nanostructure coating on stainless steel

for cardiovascular stents and its use for drug delivery’, J. Nanosci.

Nanotechnol., 2006, 6, (9–10), 3163–3170.

52. P. H. Chua, K. G. Neoh, E. T. Kang, W. Wang: ‘Surface

functionalization of titanium with hyaluronic acid/chitosan

polyelectrolyte multilayers and RGD for promoting osteoblast

functions and inhibiting bacterial adhesion’, Biomaterials, 2008,

29, (10), 1412–1421.

53. Q. K. Lin, K. F. Ren, J. Ji: ‘Hyaluronic acid and chitosan–DNA

complex multilayered thin film as surface-mediated nonviral gene

delivery system’, Colloids Surf. B Biointerfaces, 2009, 74, (1), 298–

303.

54. J. S. Moskowitz, M. R. Blaisse, R. E. Samuel, H. P. Hsu, M. B.

Harris, S. D. Martin, J. C. Lee, M. Spector, P. T. Hammond: ‘The

effectiveness of the controlled release of gentamicin from

polyelectrolyte multilayers in the treatment of staphylococcus



http://www.maneyonline.com/action/showLinks?crossref=10.1016%2Fj.biomaterials.2010.04.011&isi=000279719600013

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fla047833d&isi=000226614200052

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fma800186q&isi=000256393500033

http://www.maneyonline.com/action/showLinks?crossref=10.1016%2Fj.jcis.2012.04.058&isi=000305592000020

http://www.maneyonline.com/action/showLinks?crossref=10.1080%2F02652040500099612&isi=000232469000006

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fb307512p&isi=000186699900004

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fb713660a

http://www.maneyonline.com/action/showLinks?crossref=10.1002%2Fadfm.200600593&isi=000249636900007

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fbm049669e&isi=000224077000048

http://www.maneyonline.com/action/showLinks?crossref=10.1002%2Fanie.200906266&isi=000282477800004

http://www.maneyonline.com/action/showLinks?crossref=10.1016%2FS0167-577X%2802%2901061-3&isi=000181255900016

http://www.maneyonline.com/action/showLinks?crossref=10.1166%2Fsl.2006.062&isi=000249721700015

http://www.maneyonline.com/action/showLinks?crossref=10.1038%2Fnmat1716&isi=000241731800020

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fcm8003358&isi=000257279200010

http://www.maneyonline.com/action/showLinks?crossref=10.1080%2F09205063.2012.690284&isi=000316108900005


http://www.maneyonline.com/action/showLinks?crossref=10.1016%2Fj.cis.2004.07.006&isi=000225921500004

http://www.maneyonline.com/action/showLinks?crossref=10.1016%2Fj.nano.2006.11.007&isi=000245785800007


http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fnl0100015&isi=000173708200006

http://www.maneyonline.com/action/showLinks?crossref=10.1016%2Fj.addr.2011.03.012&isi=000293482300003

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fla036177z&isi=000220750300057



http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fla053368o&isi=000237593000031

http://www.maneyonline.com/action/showLinks?crossref=10.1016%2FS0927-7757%2801%2900956-6&isi=000174495800065

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fc2jm32332j&isi=000305242300033

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fb402617a&isi=000223272900004

http://www.maneyonline.com/action/showLinks?crossref=10.1016%2FS0168-3659%2802%2900322-X&isi=000180485500006

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fma00072a016&isi=A1993LZ50500016

http://www.maneyonline.com/action/showLinks?crossref=10.1002%2F1616-5195%2820010701%291%3A5%3C209%3A%3AAID-MABI209%3E3.0.CO%3B2-Y&isi=000171010800006

http://www.maneyonline.com/action/showLinks?crossref=10.1016%2Fj.colsurfb.2009.07.036&isi=000271371300044

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fbm0496155&isi=000224077000009

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fnn201793f&isi=000292055200002

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fc2tb00416j

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fa809106d&isi=000089142000002

http://www.maneyonline.com/action/showLinks?crossref=10.1002%2Fmabi.200400180&isi=000229423100011


http://www.maneyonline.com/action/showLinks?crossref=10.1016%2Fj.carbpol.2012.08.069&isi=000310253800055

http://www.maneyonline.com/action/showLinks?crossref=10.1002%2F1521-4095%28200109%2913%3A17%3C1324%3A%3AAID-ADMA1324%3E3.0.CO%3B2-L&isi=000170921100010

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fbp0495825&isi=000229605400037

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fb705419j

http://www.maneyonline.com/action/showLinks?crossref=10.1016%2F0040-6090%2894%2990575-4&isi=A1994NN33000025

http://www.maneyonline.com/action/showLinks?crossref=10.1016%2Fj.jconrel.2006.01.015&isi=000237263100010

aureus infection in a rabbit bone model’, Biomaterials, 2010, 31,

(23), 6019–6030.

55. X. D. Liu, W. T. Yu, W. Wang, Y. Xiong, X. J. Ma, Q. A. Yuan:

‘Polyelectrolyte microcapsules prepared by alginate and chitosan

for biomedical application’, Prog. Chem., 2008, 20, (1), 126–139.

56. C. Y. Wang, S. Q. Ye, L. Dai, X. X. Liu, Z. Tong: ‘Enhanced

resistance of polyelectrolyte multilayer microcapsules to pepsin

erosion and release properties of encapsulated indomethacin’,


57. S. F Yan, J. Zhu, Z. C. Wang, J. B. Yin, Y. Z. Zheng, X. S. Chen:

‘Layer-by-layer assembly of poly(L-glutamic acid)/chitosan micro-

capsules for high loading and sustained release of 5-fluorouracil’,

Eur. J. Pharm. Biopharm., 2011, 78, (3), 336–345.

58. D. Cui, J. Jing, T. Boudou, I. Pignot-Paintrand, S. De Koker,

B. G. De Geest, C. Picart, R. Auzely-Velty: ‘Hydrophobic shell

loading of biopolyelectrolyte capsules’, Adv. Mater., 2011, 23,

(24), H200–H204.

59. A. L. Hillberg, M. Tabrizian: ‘Biorecognition through layer-by-

layer polyelectrolyte assembly: In situ hybridization on living

cells’, Biomacromolecules, 2006, 7, (10), 2742–2750.

60. W. J. Zhang, S. T. Zhao, W. Rao, J. Snyder, J. K. Choi, J. F.

Wang, I. A. Khan, N. B. Saleh, P. J. Mohler, J. H. Yu, T. J.

Hund, C. B. Tang, X. M. He: ‘A novel core-shell microcapsule for

encapsulation and 3D culture of embryonic stem cells’, J. Mater.

Chem. B, 2013, 1, (7), 1002–1009.

61. B. G. De Geest, C. Dejugnat, G. B. Sukhorukov, K. Braeckmans,

S. C. De Smedt, J. Demeester: ‘Self-rupturing microcapsules’,

Adv. Mater., 2005, 17, (19), 2357–2361.

62. R. D. Jayant, M. J. McShane, R. Srivastava: ‘Polyelectrolyte-

coated alginate microspheres as drug delivery carriers for

dexamethasone release’, Drug Deliv., 2009, 16, (6), 331–340.

63. Q. H. Zuo, J. B. Lu, A. Hong, D. G. Zhong, S. S. Xie, Q. Liu,

Y. X. Huang, Y. F. Shi, L. M. He, W. Xue: ‘Preparation and

characterization of PEM-coated alginate microgels for controlled

release of protein’, Biomed. Mater., 2012, 7, (3), 035012.

64. H. G. Zhu, R. Srivastava, J. Q. Brown, M. J. McShane:

‘Combined physical and chemical immobilization of glucose

oxidase in alginate microspheres improves stability of encapsula-

tion and activity’, Bioconjugate Chem., 2005, 16, (6) 1451–1458.

65. E. W. Stein, P. S. Grant, H. G. Zhu, M. J. McShane: ‘Microscale

enzymatic optical biosensors using mass transport limiting

nanofilms. 1. Fabrication and characterization using glucose as

a model analyte’, Anal. Chem., 2007, 79, (4), 1339–1348.

66. E. W. Stein, S. Singh, M. J. McShane: ‘Microscale enzymatic

optical Biosensors using mass transport limiting hanofilms. 2.

Response modulation by varying analyte transport properties’,

Anal. Chem., 2008, 80, (5), 1408–1417.

67. T. Shutava, M. Prouty, D. Kommireddy, Y. Lvov: ‘pH responsive

decomposable layer-by-layer nanofilms and capsules on the basis

of tannic acid’, Macromolecules, 2005, 38, (7), 2850–2858.

68. V. Kozlovskaya, S. A. Sukhishvili: ‘pH-controlled permeability of

layered hydrogen-bonded polymer capsules’, Macromolecules,

2006, 39, (16), 5569–5572.

69. L. I. Kazakova, L. I. Shabarchina, G. B. Sukhorukov: ‘Co-

encapsulation of enzyme and sensitive dye as a tool for fabrication

of microcapsule based sensor for urea measuring’, Phys. Chem.

Chem. Phys., 2011, 13, (23), 11110–11117.

70. Z. W. Mao, L. Ma, J. Zhou, C. Y. Gao, J. C. Shen: ‘Bioactive thin

film of acidic fibroblast growth factor fabricated by layer-by-layer

assembly’, Bioconjug. Chem., 2005, 16, (5), 1316–1322.

71. A. Shukla, K. E. Fleming, H. F. Chuang, T. M. Chau, C. R.

Loose, G. N. Stephanopoulos, P. T. Hammond: ‘Controlling the

release of peptide antimicrobial agents from surfaces’,

Biomaterials, 2010, 31, (8), 2348–2357.

72. M. L. Macdonald, N. M. Rodriguez, N. J. Shah, P. T. Hammond:

‘Characterization of tunable FGF-2 releasing polyelectrolyte

multilayers’, Biomacromolecules, 2010, 11, (8), 2053–2059.

73. T. G. Shutava, S. S. Balkundi, Y. M. Lvov: ‘(-)-Epigallocatechin

gallate/gelatin layer-by-layer assembled films and microcapsules’,

J. Colloid Interface Sci., 2009, 330, (2), 276–283.

74. N. G. Balabushevich, G. B. Sukhorukov, N. A. Moroz, D. V.

Volodkin, N. I. Larionova, E. Donath, H. Mohwald: ‘Encapsulation

of proteins by layer-by-layer adsorption of polyelectrolytes onto

protein aggregates: factors regulating the protein release’, Biotechnol.

Bioeng., 2001, 76, (3), 207–213.

75. N. G. Balabushevich, V. A. Izumrudov, N. I. Larionova: ‘Protein

microparticles with controlled stability prepared via layer-by-layer

adsorption of biopolyelectrolytes’, Polym. Sci., Ser. A, 2012, 54,

(7), 540–551.

76. Z. She, M. N. Antipina, J. Li, G. B. Sukhorukov: ‘Mechanism of

protein release from polyelectrolyte multilayer microcapsules’,


77. Z. She, C. X. Wang, J. Li, G. B. Sukhorukov, M. N. Antipina:

‘Encapsulation of basic fibroblast growth factor by polyelec-

trolyte multilayer microcapsules and its controlled release for

enhancing cell proliferation’, Biomacromolecules, 2012, 13, (7),

2174–2180.

78. Y. Itoh, M. Matsusaki, T. Kida, M. Akashi: ‘Locally controlled

release of basic fibroblast growth factor from multilayered

capsules’, Biomacromolecules, 2008, 9, (8), 2202–2206.

79. L. J. De Cock, O. De Wever, S. Van Vlierberghe, E.

Vanderleyden, P. Dubruel, F. De Vos, C. Vervaet, J. P. Remon,

B. G. De Geest: ‘Engineered (hep/pARG)(2) polyelectrolyte

capsules for sustained release of bioactive TGF-beta 1’, Soft

Mater., 2012, 8, (4) 1146–1154.

80. M. Dierendonck, S. De Koker, C. Vervaet, J. P. Remon, B. G. De

Geest: ‘Interaction between polymeric multilayer capsules and

immune cells’, J. Controlled Release, 2012, 161, (2), 592–599.

81. L. J. De Cock, J. Lenoir, S. De Koker, V. Vermeersch, A. G.

Skirtach, P. Dubruel, E. Adriaens, C. Vervaet, J. P. Remon, B. G.

De Geest: ‘Mucosal irritation potential of polyelectrolyte multi-

layer capsules’, Biomaterials, 2011, 32, (7) 1967–1977.

82. R. De Rose, A. N. Zelikin, A. P. R. Johnston, A. Sexton, S. F.

Chong, C. Cortez, W. Mulholland, F. Caruso, S. J. Kent:

‘Binding, internalization, and antigen presentation of vaccine-

loaded nanoengineered capsules in blood’, Adv. Mater., 2008, 20,

(24), 4698–4703.

83. A. Sexton, P. G. Whitney, S. F. Chong, A. N. Zelikin, A. P. R.

Johnston, R. De Rose, A. G. Brooks, F. Caruso, S. J. Kent: ‘A

protective vaccine delivery system for in vivo T cell stimulation

using nanoengineered polymer hydrogel capsules’, ACS Nano,

2009, 3, (11), 3391–3400.

84. S. De Koker, B. G. De Geest, S. K. Singh, R. De Rycke,

T. Naessens, Y. Van Kooyk, J. Demeester, S. C. De Smedt,

J. Grooten: ‘Polyelectrolyte microcapsules as antigen delivery

vehicles to dendritic cells: uptake, processing, and cross-presenta-

tion of encapsulated antigens’, Angew. Chem. Int. Ed., 2009, 48,

(45), 8485–8489.

85. B. G. De Geest, M. A. Willart, H. Hammad, B. N. Lambrecht,

C. Pollard, P. Bogaert, M. De Filette, X. Saelens, C. Vervaet, J. P.

Remon, J. Grooten, S. De Koker: ‘Polymeric multilayer capsule-

mediated vaccination induces protective immunity against cancer

and viral infection’, ACS Nano, 2012, 6, (3), 2136–2149.

86. S. De Koker, T. Naessens, B. G. De Geest, P. Bogaert,

J. Demeester, S. De Smedt, J. Grooten: ‘Biodegradable polyelec-

trolyte microcapsules: antigen delivery tools with Th17 skewing

activity after pulmonary delivery’, J. Immunol., 2010, 184, (1),

203–211.

87. W. C. Mak, K. Y. Cheung, D. Trau, A. Warsinke, F. Scheller,

R. Renneberg: ‘Electrochemical bioassay utilizing encapsulated

electrochemical active microcrystal biolabels’, Anal. Chem., 2005,

77, (9), 2835–2841.

88. C. Cortez, E. Tomaskovic-Crook, A. P. R. Johnston, B. Radt,

S. H. Cody, A. M. Scott, E. C. Nice, J. K. Heath, F. Caruso:

‘Targeting and uptake of multilayered particles to colorectal

cancer cells’, Adv. Mater., 2006, 18, (15), 1998–2003.

89. N. Habibi, L. Pastorino, F. C. Soumetz, F. Sbrana, R. Raiteri,

C. Ruggiero: ‘Nanoengineered polymeric S-layers based capsules

with targeting activity’, Colloids Surf., B, 2011, 88, (1), 366–372.

90. M. M. J. Kamphuis, A. P. R. Johnston, G. K. Such, H. H. Dam,

R. A. Evans, A. M. Scott, E. C. Nice, J. K. Heath, F. Caruso:

‘Targeting of cancer cells using click-functionalized polymer

capsules’, J. Am. Chem. Soc., 2010, 132, (45), 15881–15883.

91. A. P. R. Johnston, M. M. J. Kamphuis, G. K. Such, A. M. Scott,

E. C. Nice, J. K. Heath, F. Caruso: ‘Targeting cancer cells:

controlling the binding and internalization of antibody-functio-

nalized capsules’, ACS Nano, 2012, 6, (8), 6667–6674.

92. B. Zebli, A. S. Susha, G. B. Sukhorukov, A. L. Rogach, W. J.

Parak: ‘Magnetic targeting and cellular uptake of polymer

microcapsules simultaneously functionalized with magnetic and

luminescent nanocrystals’, Langmuir, 2005, 21, (10), 4262–4265.

93. R. A. Stull, F. C. Szoka: ‘Antigene, ribozyme and aptamer

nucleic-acid drugs: progress and prospects’, Pharm. Res., 1995, 12,

(4), 465–483.

94. S. D. Patil, D. G. Rhodes, D. J. Burgess: ‘DNA-based

therapeutics and DNA delivery systems: a comprehensive review’,

AAPS J., 2005, 7, (1), E61–E77.

95. D. Putnam: ‘Polymers for gene delivery across length scales’, Nat.

Mater., 2006, 5, (6), 439–451.



http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fc1sm06618h

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fbm100413w&isi=000280583400021

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fja106405c&isi=000284202200016

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fac061414z&isi=000244206300010

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fnn900715g&isi=000271951200010


http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fbm901450r&isi=000277355800014

http://www.maneyonline.com/action/showLinks?crossref=10.1208%2Faapsj070109&isi=000234991000009

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fc1cp20354a&isi=000291113200026


http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fac048505l&isi=000228877500032


http://www.maneyonline.com/action/showLinks?isi=000253022000016


http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fnn3010476&isi=000307988900018

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fac701738e&isi=000253560900019


http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fbm060266j&isi=000241106600008

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fbm3005879&isi=000306151700021

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fbc049755b&isi=000232070200036

http://www.maneyonline.com/action/showLinks?crossref=10.1038%2Fnmat1645&isi=000237968100015

http://www.maneyonline.com/action/showLinks?crossref=10.1088%2F1748-6041%2F7%2F3%2F035012



http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fbm070110z&isi=000246413600046

http://www.maneyonline.com/action/showLinks?crossref=10.1002%2Fbit.1184&isi=000171855700004

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fla0502286&isi=000228983700004

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fma047629x&isi=000228067600043

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fc2tb00058j

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fnn205099c&isi=000301945900027



http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fbc050171z&isi=000233393800017

http://www.maneyonline.com/action/showLinks?crossref=10.1016%2Fj.colsurfb.2011.07.015&isi=000295344800051


http://www.maneyonline.com/action/showLinks?crossref=10.1016%2Fj.ejpb.2010.12.031&isi=000294105600005

http://www.maneyonline.com/action/showLinks?crossref=10.1134%2FS0965545X12040098&isi=000306496000004

http://www.maneyonline.com/action/showLinks?crossref=10.1023%2FA%3A1016281324761&isi=A1995QT97200001

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fma0607923&isi=000239400800056


http://www.maneyonline.com/action/showLinks?crossref=10.4049%2Fjimmunol.0803591&isi=000272985300025

96. W. Walther, U. Stein: ‘Viral vectors for gene transfer: a review of

their use in the treatment of human diseases’, Drugs, 2000, 60, (2),

249–271.

97. E. Fattal, J. Delattre, C. Dubernet, P. Couvreur: ‘Liposomes for

the delivery of nucleotides and oligonucleotides’, S. T. P. Pharma

Sci., 1999, 9, (5), 383–390.

98. M. C. Pedroso de Lima, S. Simoes, P. Pires, H. Faneca,

N. Duzgunes: ‘Cationic lipid–DNA complexes in gene delivery:

from biophysics to biological applications’, Adv. Drug Delivery

Rev., 2001, 47, (2–3), 277–294.

99. T. Merdan, J. Kopecek, T. Kissel: ‘Prospects for cationic

polymers in gene and oligonucleotide therapy against cancer’,

Adv. Drug Delivery Rev., 2002, 54, (5), 715–758.

100. T. G. Park, J. H. Jeong, S. W. Kim ‘Current status of polymeric

gene delivery systems’ Adv. Drug Delivery Rev., 2006, 58, (4) 467–

486.

101. M. N. Antipina, I. Schulze, M. Heinze, B. Dobner, A. Langner,

G. Brezesinski: ‘Physical–chemical properties and transfection

activity of cationic lipid/DNA complexes’, Chem. Phys. Chem.,

2009, 10, (14), 2471–2479.

102. G. Borchard: ‘Chitosans for gene delivery’, Adv Drug Delivery

Rev., 2001, 52, (2), 145–150.

103. J. G. LeHoux, F. Grondin: ‘Some effects of chitosan on liver

function in the rat’, Endocrinology, 1993, 132, (3), 1078–1084.

104. B. G. De Geest, R. E. Vandenbroucke, A. M. Guenther, G. B.

Sukhorukov, W. E. Hennink, N. N. Sanders, J. Demeester, S. C.

De Smedt: ‘Intracellularly degradable polyelectrolyte microcap-

sules’, Adv. Mater., 2006, 18, (8), 1005–1009.

105. G. B. Sukhorukov, H. Moehwald, G. Decher, Y. M. Lvov.

‘Assembly of polyelectrolyte multilayer films by consecutively

alternating adsorption of polynucleotides and polycations’, Thin

Solid Films, 1996, 284–285, 220–223.

106. C. Schueler, F. Caruso: ‘Decomposable hollow biopolymer-based

capsules’, Biomacromolecules, 2001, 2, (3) 921–926.

107. D. G. Shchukin, A. A. Patel, G. B. Sukhorukov, Y. M. Lvov:

‘Nanoassembly of biodegradable microcapsules for DNA encas-

ing’, J. Am. Chem. Soc., 2004, 126, (11) 3374–3375.

108. A. Fujii, Y. Ohmukai, T. Maruyama, T. Sotani, H. Matsuyama:

‘Preparation of DNA capsules cross-linked through NeutrAvidin–

biotin interaction’, Colloids Surf., A, 2011, 384, (1–3) 529–535.

109. U. Reibetanz, C. Claus, E. Typlt, J. Hofmann, E. Donath:

‘Defoliation and plasmid delivery with layer-by-layer coated

colloids’, Macromol. Biosci., 2006, 6, (2), 153–160.

110. A. Elbakry, A. Zaky, R. Liebl, R. Rachel, A. Goepferich,

M. Breunig: ‘Layer-by-layer assembled gold nanoparticles for

siRNA delivery’, Nano Lett., 2009, 9, (5), 2059–2064.

111. A. P. R. Johnston, E. S. Read, F. Caruso: ‘DNA multilayer films

on planar and colloidal supports: Sequential assembly of like-

charged polyelectrolytes’, Nano Lett., 2005, 5, (5), 953–956.

112. A. P. R. Johnston, H. Mitomo, E. S. Read, F. Caruso:

‘Compositional and structural engineering of DNA multilayer

films’, Langmuir, 2006, 22, (7), 3251–3258.

113. A. S. Angelatos, A. P. R. Johnston, Y. J. Wang, F. Caruso:

‘Probing the permeability of polyelectrolyte multilayer capsules

via a molecular beacon approach’, Langmuir, 2007, 23, (8) 4554–

4562.

114. O. Kreft, R. Georgieva, H. Baeumler, M. Steup, B. Mueller-

Rober, G. B. Sukhorukov, H. Moehwald: ‘Red blood cell

templated polyelectrolyte capsules: a novel vehicle for the stable

encapsulation of DNA and proteins’, Macromol. Rapid Commun.,

2006, 27, (6), 435–440.

115. T. Borodina, E. Markvicheva, S. Kunizhev, H. Moehwald, G. B.

Sukhorukov, O. Kreft: ‘Controlled release of DNA from self-

degrading microcapsules’, Macromol. Rapid Commun., 2007, 28,

(18–19), 1894–1899.

116. A. N. Zelikin, Q. Li, F. Caruso: ‘Degradable polyelectrolyte

capsules filled with oligonucleotide sequences’, Angew. Chem. Int.

Ed., 2006, 45, (46) 7743–7745.

117. A. N. Zelikin, A. L. Becker, A. P. R. Johnston, K. L. Wark,

F. Turatti, F. Caruso: ‘A general approach for DNA encapsula-

tion in degradable polymer Microcapsules’, ACS Nano, 2007, 1,

(1) 63–69.

118. A. P. R. Johnston, A. N. Zelikin, F. Caruso: ‘Assembling DNA

into advanced materials: From nanostructured films to Biosensing

and delivery systems’, Adv. Mater., 2007, 19, (21), 3727–3730.

119. S. Moya, G. B. Sukhorukov, M. Auch, E. Donath, H. Moehwald:

‘Microencapsulation of organic solvents in polyelectrolyte multi-

layer micrometer-sized shells’, J. Colloid Interface Sci., 1999, 216,

(2), 297–302.

120. S. Sivakumar, V. Bansal, C. Cortez, S. F. Chong, A. N. Zelikin,

F. Caruso: ‘Degradable, surfactant-free, monodisperse polymer-

encapsulated emulsions as anticancer drug carriers’, Adv. Mater.,

2009, 21, (18), 1820–1824.

121. M. V. Kiryukhin, S. M. Man, S. R. Gorelik, G. S. Subramanian,

H. Y. Low, G. B. Sukhorukov: ‘Fabrication and mechanical

properties of microchambers made of polyelectrolyte multilayers’,

Soft Matter., 2011, 7, (14), 6550–6556.

122. J. R. Mancuso, D. J. McClements, E. A. Decker: ‘The effects of

surfactant type, pH, and chelators on the oxidation of salmon oil-

in-water emulsions’, J. Agric. Food Chem., 1999, 47, (10), 4112–

4116.

123. U. Klinkesorn, P. Sophanodora, P. Chinachoti, D. J.

McClements, E. A. Decker: ‘Increasing the oxidative stability of

liquid and dried tuna oil-in-water emulsions with electrostatic

layer-by-layer deposition technology’, J. Agric. Food Chem., 2005,

53, (11) 4561–4566.

124. D. O. Grigoriev, T. Bukreeva, H. Moehwald, D. G. Shchukin:

‘New method for fabrication of loaded micro- and nanocontai-

ners: emulsion encapsulation by polyelectrolyte layer-by-layer

deposition on the liquid core’, Langmuir, 2008, 24, (3), 999–1004.

125. H. Wackerbarth, P. Schoen, U. Bindrich: ‘Preparation and

characterization of multilayer coated microdroplets: droplet

deformation simultaneously probed by atomic force spectroscopy

and optical detection’, Langmuir, 2009, 25, (5), 2636–2640.

126. K. Szczepanowicz, D. Dronka-Gora, G. Para, P. Warszynski:

‘Encapsulation of liquid cores by layer-by-layer adsorption of

polyelectrolytes’, J. Microencapsulation, 2010, 27, (3), 198–204.

127. M. V. Lomova, G. B. Sukhorukov, M. N. Antipina: ‘Antioxidant

coating of micronsize droplets for prevention of lipid peroxidation

in oil-in-water emulsion’, ACS Appl. Mater. Interfaces, 2010, 2,

(12), 3669–3676.

128. A. V. Sadovoy, M. V. Kiryukhin, G. B. Sukhorukov, M. N.

Antipina: ‘Kinetic stability of water-dispersed oil droplets

encapsulated in a polyelectrolyte multilayer shell’, Phys. Chem.

Chem. Phys., 2011, 13, (9), 4005–4012.

129. E. Tjipto, K. D. Cadwell, J. F. Quinn, A. P. R. Johnston, N. L.

Abbott, F. Caruso: ‘Tailoring the interfaces between nematic

liquid crystal emulsions and aqueous phases via layer-by-layer

assembly’, Nano Lett., 2006, 6, (10), 2243–2248.

130. J. L. Donnelly, E. A. Decker, D. J. McClements: ‘Iron-catalyzed

oxidation of Menhaden oil as affected by emulsifiers’, J. Food Sci.,

1998, 63, (6), 997–1000.

131. M. Hu, D. J. McClements, E. A. Decker: ‘Impact of whey protein

emulsifiers on the oxidative stability of salmon oil-in-water

emulsions’, J. Agric. Food Chem., 2003, 51, (5), 1435–1439.

132. S. Ogawa, E. A. Decker, D. J. McClements: ‘Influence of

environmental conditions on the stability of oil in water emulsions

containing droplets stabilized by lecithin–chitosan membranes’,

J. Agric. Food Chem., 2003, 51, (18), 5522–5527.

133. G. B. Sukhorukov, E. Donath, S. Moya, A. S. Susha, A. Voigt,

J. Hartmann, H. Moehwald: ‘Microencapsulation by means of

step-wise adsorption of polyelectrolytes’, J. Microencapsulation,

2000, 17, (2), 177–185.

134. X. Y. Liu, C. Y. Gao, J. C. Shen, H. Moehwald: ‘Multilayer

microcapsules as anti-cancer drug delivery vehicle: deposition,

sustained release, and in vitro bioactivity’, Macromol. Biosci.,

2005, 5, (12), 1209–1219.

135. A. J. Khopade, F. Caruso: ‘Stepwise self-assembled poly(amidoa-

mine) dendrimer and poly(styrenesulfonate) microcapsules as

sustained delivery vehicles’, Biomacromolecules, 2002, 3, (6), 1154–

1162.

136. Q. H. Zhao, S. A. Zhang, W. J. Tong, C. Y. Gao, J. C. Shen:

‘Polyelectrolyte microcapsules templated on poly(styrene sulfo-

nate)-doped CaCO3 particles for loading and sustained release of

daunorubicin and doxorubicin’, Eur. Polym. J., 2006, 42, (12),

3341–3351.

137. B. S. Han, B. Y. Shen, Z. H. Wang, M. M. Shi, H. W. Li, C. H.

Peng, Q. H. Zhao: ‘Layered microcapsules for daunorubicin

loading and release as well as in vitro and in vivo studies’, Polymer.

Adv. Tech., 2008, 19, (1), 36–46.

138. H. J. Shen, H. Shi, K. Ma, M. Xie, L. L. Tang, S. Shen, B. Li,

X. S. Wang, Y. Jin: ‘Polyelectrolyte capsules packaging BSA gels

for pH-controlled drug loading and release and their antitumor

activity’, Acta Biomater., 2013, 9, (4), 6123–6133.

139. C. J. Ochs, G. K. Such, Y. Yan, M. P. van Koeverden, F. Caruso:

‘Biodegradable click capsules with engineered drug-loaded multi-

layers’, ACS Nano, 2010, 4, (3) 1653–1663.

140. G. F. Luo, X. D. Xu, J. Zhang, J. Yang, Y. H. Gong, Q. Lei,

H. Z. Jia, C. Li, R. X. Zhuo, X. Z. Zhang: ‘Encapsulation of an



http://www.maneyonline.com/action/showLinks?crossref=10.1006%2Fjcis.1999.6286&isi=000081986400011

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fla052581h&isi=000236843300054

http://www.maneyonline.com/action/showLinks?crossref=10.1002%2Fpat.966&isi=000253384800005

http://www.maneyonline.com/action/showLinks?crossref=10.1111%2Fj.1365-2621.1998.tb15841.x&isi=000077750300015

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fjf0479158&isi=000229405000038





http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fam100818j



http://www.maneyonline.com/action/showLinks?crossref=10.1016%2FS0169-409X%2801%2900110-7

http://www.maneyonline.com/action/showLinks?crossref=10.1016%2Fj.actbio.2012.12.024&isi=000316526700024

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fjf0203794&isi=000181087100053


http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fla702873f&isi=000252777700062

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fnn700063w&isi=000252012200013


http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fbm025562k&isi=000179236500004

http://www.maneyonline.com/action/showLinks?isi=A1993KP29000020

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fc0cp01762k&isi=000287411700051

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fc1sm05101f&isi=000292985500025

http://www.maneyonline.com/action/showLinks?crossref=10.1002%2Fmarc.200500777&isi=000236600500009



http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fjf026103d&isi=000184941500052

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fja036952x&isi=000220286400003


http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fla802898k&isi=000263770800018


http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fnl050608b&isi=000229120900025

http://www.maneyonline.com/action/showLinks?crossref=10.2165%2F00003495-200060020-00002&isi=000089073300002

http://www.maneyonline.com/action/showLinks?crossref=10.1016%2Fj.eurpolymj.2006.09.005&isi=000243035200021


http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fnl061604p&isi=000241157300014

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fjf990203a&isi=000083242100028

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fam301258a

http://www.maneyonline.com/action/showLinks?crossref=10.1002%2Fmarc.200700409


http://www.maneyonline.com/action/showLinks?crossref=10.1016%2Fj.colsurfa.2011.05.021

http://www.maneyonline.com/action/showLinks?crossref=10.1002%2Fcphc.200900069


adamantane–doxorubicin prodrug in pH-responsive polysacchar-

ide capsules for controlled release’, ACS Appl. Mater. Interfaces,

2012, 4, (10), 5317–5324.

141. D. V. Andreeva, D. A. Gorin, H. Moehwald, G. B. Sukhorukov:

‘Novel type of self-assembled polyamide and polyimide nanoen-

gineered shells – fabrication of microcontainers with shielding

properties’, Langmuir, 2007, 23, (17), 9031–9036.

142. B. Thierry, P. Kujawa, C. Tkaczyk, F. M. Winnik, L. Bilodeau,

M. Tabrizian: ‘Delivery platform for hydrophobic drugs: prodrug

approach combined with self-assembled multilayers’, J. Am.

Chem. Soc., 2005, 127, 1626–1627.

143. T. Boudou, P. Kharkar, J. Jing, R. Guillot, I. Pignot-Paintrand,

R. Auzely-Velty, C. Picart: ‘Polyelectrolyte multilayer nanoshells

with hydrophobic nanodomains for delivery of Paclitaxel’,

J. Controlled Release, 2012, 159, (3), 403–412.

144. C. Vodouhe, E. Le Guen, J. M. Garza, G. Francius, C. Dejugnat,

J. Ogier, P. Schaaf, J. C. Voegel, P. Lavalle: ‘Control of drug

accessibility on functional polyelectrolyte multilayer films’,

Biomaterials, 2006, 27, (22), 4149–4156.

145. A. S. Zahr, M. V. Pishko: ‘Encapsulation of paclitaxel in

macromolecular nanoshells’, Biomacromolecules, 2007, 8, (6),

2004–2010.

146. I. L. Radtchenko, M. Giersig, G. B. Sukhorukov: ‘Inorganic

particle synthesis in confined micron-sized polyelectrolyte cap-

sules’, Langmuir, 2002, 18, (21), 8204–8208.

147. D. G. Shchukin, I. L. Radtchenko, G. B. Sukhorukov: ‘Synthesis

of nanosized magnetic ferrite particles inside hollow polyelec-

trolyte capsules’, J. Phys. Chem. B, 2003, 107, (1), 86–90.

148. I. L. Radtchenko, G. B. Sukhorukov, H. Moehwald: ‘A novel

method for encapsulation of poorly water-soluble drugs: pre-

cipitation in polyelectrolyte multilayer shells’, Int. J. Pharm.,

2002, 242, (1–2), 219–223.

149. G. B. Sukhorukov, L. Daehne, J. Hartmann, E. Donath, H.

Moehwald: ‘Controlled precipitation of dyes into hollow poly-

electrolyte capsules based on colloids and biocolloids’, Adv.

Mater., 2000, 12, (2), 112–115.

150. O. Kreft, M. Prevot, H. Moehwald, G. B. Sukhorukov: ‘Shell-in-

shell microcapsules: a novel tool for integrated, spatially confined

enzymatic reactions’, Angew. Chem., Int. Ed., 2007, 46, (29), 5605–

5608.

151. M. N. Antipina, M. V. Kiryukhin, K. Chong, H. Y. Low, G. B.

Sukhorukov: ‘Patterned microcontainers as novel functional

elements for mTAS and LOC’, Lab Chip, 2009, 9, (10), 1472–1475.

152. A. G. Skirtach, A. M. Yashchenok, H. Mohwald: ‘Encapsulation,

release and applications of LbL polyelectrolyte multilayer

capsules’, Chem. Commun., 2011, 47, (48), 12736–12746.

153. M. Delcea, H. Moehwald, A. G. Skirtach: ‘Stimuli responsive

LbL capsules and nanoshells for drug delivery’, Adv. Drug Del.

Rev., 2011, 63, (9), 730–747.

154. W. B. Stockton, M. F. Rubner: ‘Layer-by-layer manipulation of

polyaniline via hydrogen-bonding interactions’, Macromolecules,

1997, 30, (9), 2717–2725.

155. T. Mauser, C. Dejugnat, G. B. Sukhorukov: ‘Reversible pH-

dependent properties of multilayer microcapsules made of weak

polyelectrolytes’, Macromol. Rapid Commun., 2004, 25, (20),

1781–1785.

156. J. Yun, H. I. Kim: ‘Control of release characteristics in pH-

sensitive poly(vinyl alcohol)/poly(acrylic acid) microcapsules

containing chemically treated alumina core’, J. Appl. Polym.

Sci., 2010, 115, (3), 1853–1858

157. Q. H. Zhao, B. Y. Li: ‘pH-controlled drug loading and release

from biodegradable microcapsules’, Nanomed. Nanotechnol. Biol.

Med., 2008, 4, (4), 302–310.

158. E. Kharlampieva, V. Kozlovskaya, S. A. Sukhishvili: ‘Layer-by-

layer hydrogen-bonded polymer films: From fundamentals to

applications’, Adv. Mater., 2009, 21, (30), 3053–3065.

159. S. A. Sukhishvili, S. Granick: ‘Layered, erasable, ultrathin

polymer films’, J. Am. Chem. Soc., 2000, 122, (39), 9550–9551.

160. S. E. Burke, C. J. Barrett: ‘pH-responsive properties of multilayered

poly(L-lysine)/hyaluronic acid surfaces’, Biomacromolecules, 2003,

4, (6), 1773–1783.

161. V. Kozlovskaya, E. Kharlampieva, I. Drachuk, D. Cheng, V. V.

Tsukruk: ‘Responsive microcapsule reactors based on hydrogen-

bonded tannic acid layer-by-layer assemblies’, Soft Matter., 2010,

6, 3596–3608.

162. T. Crouzier, T. Boudou, C. Picart: ‘Polysaccharide-based poly-

electrolyte multilayers’, Curr. Opinion Colloid Interface Sci., 2010,

15, (6), 417–426.

163. I. Drachuk, O. Shchepelina, M. Lisunova, S. Harbaugh, N.

Kelley-Loughnane, M. Stone, V. V. Tsukruk: ‘pH-responsive

Layer-by-layer nanoshells for direct regulation of cell activity’,

ACS Nano, 2012, 6, (5), 4266–4278.

164. C. H. Ye, I. Drachuk, R. Calabrese, H. Q. Dai, D. L. Kaplan,

V. V. Tsukruk: ‘Permeability and micromechanical properties of

silk ionomer microcapsules’, Langmuir, 2012, 28, (33), 12235–

12244.

165. X. Huang, D. Appelhans, P. Formanek, F. Simon, B. Voit:

‘Tailored synthesis of intelligent polymer nanocapsules: An

investigation of controlled permeability and pH-dependent

degradability’, ACS Nano, 2012, 6, (11), 9718–9726.

166. T. Kida, M. Mouri, K. Kondo, M. Akashi: ‘Controlled release

using a polymer stereocomplex capsule through the selective

extraction and incorporation of one capsule shell component’,

Langmuir, 2012, 28, (43), 15378–15384.

167. A. A. Antipov, G. B. Sukhorukov, H. Moehwald: ‘Influence of

the ionic strength on the polyelectrolyte multilayers’ permeability’,

Langmuir, 2003, 19, (6), 2444–2448.

168. C. Gao, H. Moehwald, J. Shen: ‘Enhanced biomacromolecule

encapsulation by swelling and shrinking procedures’, ChemPhysChem,

2004, 5, (1), 116–120.

169. R. J. Zhang, K. Koehler, O. Kreft, A. Skirtach, H. Moehwald,

G. B. Sukhorukov: ‘Salt-induced fusion of microcapsules of

polyelectrolytes’, Soft Matter., 2010, 6, (19), 4742–4747.

170. K. Riske, R. Dimova: ‘Timescales involved in electro-deforma-

tion, poration and fusion of giant vesicles resolved with fast digital

imaging’, Biophys. J., 2005, 88, (2), 1143–1155.

171. Y. Lvov, A. Antipov, A. Mamedov, H. Moehwald, G. B.

Sukhorukov: ‘Urease encapsulation in nanoorganized micro-

shells’, Nano Lett., 2001, 1, (3), 125–128.

172. M. A. Trojer, Y, Li, C. Abrahamsson, A. Mohamed, J. Eastoe,

K. Holmberg, M. Nyden: ‘Charged microcapsules for controlled

release of hydrophobic actives. Part I: encapsulation methodology

and interfacial properties’, Soft Matter., 2013, 9, (5), 1468–1477.

173. P. M. Mendes: ‘Stimuli-responsive surfaces for bio-applications’,

Chem. Soc. Rev., 2008, 37, (11), 2512–2529.

174. G. Rydzek, J. S. Thomann, N. Ben Ameur, L. Jierry, P. Mesini,

A. Ponche, C. Contal, A. E. El Haitami, J. C. Voegel, B. Senger,

P. Schaaf, B. Frisch, F. Boulmedais: ‘Polymer multilayer films

obtained by electrochemically catalyzed click chemistry’,

Langmuir, 2010, 26, (4), 2816–2824.

175. R. Zahn, J. Voros, T. Zambelli: ‘Swelling of electrochemically

active polyelectrolyte multilayers’, Curr. Opin. Colloid Interface

Sci., 2010, 15, (6), 427–434.

176. A. Baba, P. Taranekar, R. R. Ponnapati, W. Knoll, R. C.

Advincula: ‘Electrochemical surface plasmon resonance and wave

guide-enhanced glucose biosensing with n-alkylaminated poly-

pyrrole/glucose oxidase multilayers’, ACS Appl. Mater. Interfaces,

2010, 2, (8), 2347–2354.

177. H. J. Wang, S. Ishihara, K. Ariga, Y. Yamauchi: ‘All-metal

Layer-by-layer films: bimetallic alternate layers with accessible

mesopores for enhanced electrocatalysis’, J. Am. Chem. Soc.,

2012, 134, (26), 10819–10821.

178. B. G. De Geest, A. G. Skirtach, T. R. M. De Beer, G. B.

Sukhorukov, L. Bracke, W. R. G. Baeyens, J. Demeester, S. C. De

Smedt: ‘Stimuli-responsive multilayered hybrid nanoparticle/

polyelectrolyte capsules’, Macromol. Rapid Commun., 2007, 28,

(1), 88–95.

179. K. Koehler, D. G. Shchukin, H. Moehwald, G. B. Sukhorukov:

‘Thermal behavior of polyelectrolyte multilayer microcapsules. 1.

The effect of odd and even layer number’, J. Phys. Chem. B, 2005,

109, (39), 18250–18259.

180. R. Steitz, V. Leiner, K. Tauer, V. Khrenov, R. von Klitzing:

‘Temperature-induced changes in polyelectrolyte films at the

solid–liquid interface’, Appl. Phys. A: Mater. Sci. Process., 2002,

74, (1), S519–S521.

181. H. Ahrens, K. Buescher, D. Eck, S. Foerster, C. Luap, G.

Papastavrou, J. Schmitt, R. Steitz, C. A. Helm: ‘Poly(styrene

sulfonate) adsorption: Electrostatic and secondary interactions’,

Macromol. Symp., 2004, 211, (1), 93–106.

182. G. Ibarz, L. Dahne, E. Donath, H. Moehwald: ‘Controlled

permeability of polyelectrolyte capsules via defined annealing’,

Chem. Mater., 2002, 14, (10), 4059–4062.

183. C. Dejugnat, K. Koehler, M. Dubois, G. B. Sukhorukov,

H. Moehwald, T. Zemb, P. Guttmann: ‘Membrane densification

of heated polyelectrolyte multilayer capsules characterized by soft

X-ray microscopy’, Adv. Mater., 2007, 19, (10), 1331–1336.

184. O. Soltwedel, P. Nestler, H. G. Neunnann, M. Passvogel,

R. Koehler, C. A. Helm: ‘Influence of Polycation (PDADMAC)

weight on vertical diffusion within polyelectrolyte multilayers



http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fam100373v


http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fc0sm00218f&isi=000282008300017

http://www.maneyonline.com/action/showLinks?crossref=10.1016%2Fj.cocis.2010.05.007&isi=000284520000004

http://www.maneyonline.com/action/showLinks?crossref=10.1007%2Fs003390201782&isi=000181499600173


http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fb714635n&isi=000260309500014

http://www.maneyonline.com/action/showLinks?crossref=10.1016%2FS0378-5173%2802%2900145-X


http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fla303120t&isi=000310484300030

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fma301605x&isi=000309505500038

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fja002410t&isi=000089690600029

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fc1cc13453a&isi=000297364100001

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fja303773z&isi=000305863900027

http://www.maneyonline.com/action/showLinks?crossref=10.1529%2Fbiophysj.104.050310

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fbm070177m&isi=000247107900033


http://www.maneyonline.com/action/showLinks?crossref=10.1002%2Fmasy.200450707&isi=000221718800008

http://www.maneyonline.com/action/showLinks?crossref=10.1002%2Fapp.31332&isi=000272631800073


http://www.maneyonline.com/action/showLinks?crossref=10.1002%2F%28SICI%291521-4095%28200001%2912%3A2%3C112%3A%3AAID-ADMA112%3E3.0.CO%3B2-P&isi=000084981300012

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fja045077s&isi=000226951800018

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fla026101n&isi=000181562700081






http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fla302455y&isi=000307695800034

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fcm011300y&isi=000178782900012

http://www.maneyonline.com/action/showLinks?crossref=10.1016%2Fj.nano.2008.06.004&isi=000262668600005


http://www.maneyonline.com/action/showLinks?crossref=10.1016%2Fj.cocis.2010.07.006&isi=000284520000005


http://www.maneyonline.com/action/showLinks?crossref=10.1002%2Fcphc.200300761&isi=000188713300015

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fb927369g&isi=000280140800026

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fma9700486&isi=A1997WX67800027

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fjp052208i&isi=000232318500009

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fc2sm27275j&isi=000312945200009

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fjp0265236&isi=000180254900014




http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fb819725c&isi=000268227400023

during film formation and postpreparation treatment’,

Macromolecules, 2012, 45, (19), 7995–8004.

185. B. P. Timko, T. Dvir, D. S. Kohane: ‘Remotely triggerable drug

delivery systems’, Adv. Mater., 2010, 22, (44), 4925–4943.

186. Unger, E. ‘‘Drug and gene delivery with ultrasound contrast

agents’’, The Leading Edge in Diagnostic Ultrasound, Atlantic City,

NJ: May (1997): 13–16.

187. A. G. Skirtach, B. G. De Geest, A. Mamedov, A. A. Antipov,

N. A. Kotov, G. B. Sukhorukov: ‘Ultrasound stimulated release

and catalysis using polyelectrolyte multilayer capsules’, J. Mater.

Chem., 2007, 17, (11), 1050–1054.

188. A. M. Yashchenok, M. Delcea, K. Videnova, E. A. Jares-Erijman,

T. M. Jovin, M. Konrad, H. Moehwald, A. G. Skirtach: ‘Enzyme

Reaction in the pores of CaCO3 particles upon ultrasound

disruption of attached substrate-filled liposomes’, Angew. Chem.

Int. Ed., 2010, 49, (44), 8116–8120.

189. Z. Lu, M. D. Prouty, Z. Guo, V. O. Golub, C. S. Kumar, Y. M.

Lvov: ‘Magnetic switch of permeability for polyelectrolyte

microcapsules embedded with Co@Au nanoparticles’, Langmuir,

2005, 21, (5), 2042–2050.

190. K. Katagiri, M. Nakamura, K. Koumoto: ‘Magnetoresponsive

smart capsules formed with polyelectrolytes, lipid bilayers and

magnetic nanoparticles’, ACS Appl. Mater. Interfaces, 2010, 2, (3),

768–773.

191. D. A. Gorin, S. A. Portnov, O. A. Inozemtseva, Z. Luklinska,

A. M. Yashchenok, A. M. Pavlov, A. G. Skirtach, H. Moehwald,

G. B. Sukhorukov: ‘Magnetic/gold nanoparticle functionalized

biocompatible microcapsules with sensitivity to laser irradiation’,

Phys. Chem. Chem. Phys., 2008, 10, (45), 6899–6905.

192. G. Tzvetkov, B. Graf, P. Fernandes, A. Fery, F. Cavalieri,

G. Paradossi, R. Fink: ‘In situ imaging of gas-filled microballoons

by soft X-ray microscopy’, Soft Matter, 2008, 4, (3), 510–514.

193. F. Dubreuil, N. Elsner, A. Fery: ‘Elastic properties of polyelec-

trolyte capsules studied by atomic-force microscopy and RICM’,

Eur. Phys. J. E, 2003, 12, (2), 215–221.

194. O. I. Vinogradova, O. V. Lebedeva, K. Vasilev, H. F. Gong,

J. Garcia-Turiel, B. S. Kim: ‘Multilayer DNA/poly (allylamine

hydrochloride) microcapsules: assembly and mechanical proper-

ties’, Biomacromolecules, 2005, 6, (3), 1495–1502.

195. A. Munoz-Javier, O. Kreft, M. Semmling, S. Kempter, A. G.

Skirtach, O. T. Bruns, P. del Pino, M. F. Bedard, J. Raedler,

J. Kaes, C. Planck, G. B. Sukhorukov, W. J Parak: ‘Uptake of

colloidal polyelectrolyte-coated particles and polyelectrolyte

multilayer capsules by living cells’, Adv. Mater., 2008, 20, (22),

4281–4287.

196. A. M. Yashchenok, D. N. Bratashov, D. A. Gorin, M. V.

Lomova, A. M. Pavlov, A. V. Sapelkin, B. S. Shim, G. B.

Khomutov, N. A. Kotov, G. B. Sukhorukov, H. Moehwald,

A. G. Skirtach: ‘Carbon nanotubes on polymeric microcapsules:

Free-standing structures and point-wise laser openings’, Adv.

Funct. Mater., 2010, 20, (18), 3136–3142.

197. P. A. L. Fernandes, M. Delcea, A. G. Skirtach, H. Moehwald,

A. Fery: ‘Quantification of release from microcapsules upon

mechanical deformation with AFM’, Soft Matter, 2010, 6, (9),

1879–1883.

198. R. Palankar, B. E. Pinchasik, S. Schmidt, B. G. De Geest,

A. Fery, H. Moehwald, A. G. Skirtach, M. Delcea: ‘Mechanical

strength and intracellular uptake of CaCO3-templated LbL

capsules composed of biodegradable polyelectrolytes: the influ-

ence of the number of layers’, J. Mater. Chem. B, 2013, 1, (8),

1175–1181.

199. A. Roggan, M. Friebel, K. Dorschel, A. Hahn, G. Mueller:

‘Optical properties of circulating human blood in the wavelength

range 400–2500 nm’, J. Biomed. Opt., 1999, 4, (1), 36–46.

200. A. G. Skirtach, A. A. Antipov, D. G. Shchukin, G. B.

Sukhorukov: ‘Remote activation of capsules containing Ag

nanoparticles and IR dye by laser light’, Langmuir, 2004, 20,

(17), 6988–6992.

201. B. Radt, T. A. Smith, F. Caruso: ‘Optically addressable

nanostructured capsules’, Adv. Mater., 2004, 16, (23–24), 2184–

2189.

202. D. Kohler, N. Madaboosi, M. Delcea, S. Schmidt, B. G. De

Geest, D. V. Volodkin, H. Moehwald, A. G. Skirtach: ‘Patchiness

of embedded particles and film stiffness control through

concentration of gold nanoparticles,’ Adv. Mater., 2012, 24,

1095–1100.

203. a) A. G. Skirtach, C. Dejugnat, D. Braun, A. S. Susha, A. L.

Rogach, G. B. Sukhorukov: ‘Nanoparticles distribution control by

polymers: aggregates versus nonaggregates’, J. Phys. Chem. C, 2007,

111, (2), 555–564; b) B. V. Parakhonskiy, M. F. Bedard, T. V.

Bukreeva, G. B. Sukhorukov, H. Moehwald, A. G. Skirtach:

‘Nanoparticles on polyelectrolytes at low concentration: controlling

concentration and size’, J. Phys. Chem. C, 2010, 114, (5), 1996–2002.

204. A. S. Angelatos, B. Radt, F. Caruso: ‘Light-responsive polyelec-

trolyte/gold nanoparticle microcapsules’, J. Phys. Chem. B, 2005,

109, (7), 3071–3076.

205. M. F. Bedard, D. Braun, G. B. Sukhorukov, A. G. Skirtach:

‘Towards self-assembly of nanoparticles on polymeric capsules:

Release threshold and permeability’, ACS Nano, 2008, 2, (9),

1807–1816.

206. M. Bedard, A. G. Skirtach, G. B. Sukhorukov: ‘Optically driven

encapsulation using novel polymeric hollow shells containing an

azobenzene polymer’, Macromol. Rapid Commun., 2007, 28, (15),

1517–1521.

207. H. Y. Koo, H. J. Lee, J. K. Kim, W. S. Choi: ‘UV-triggered

encapsulation and release from polyelectrolyte microcapsules

decorated with photoacid generators’, J. Mater. Chem., 2010,

20, (19), 3932–3937.

208. a) A. G. Skirtach, P. Karageorgiev, M. F. Bedard, G. B.

Sukhorukov, H. Moehwald: ‘Reversibly permeable nanomem-

branes of polymeric microcapsules’, J. Am. Chem. Soc., 2008, 130,

(35), 11572–11573. b) W. Q. Jin, A. Toutianoush, B. Tieke: ‘Size-

and charge-selective transport of aromatic compounds across

polyelectrolyte multilayer membranes’, Appl. Surf. Sci., 2005, 246,

(4), 444–450.

209. A. G. Skirtach, P. Karageorgiev, B. G. De Geest, N. Pazos-Perez,

D. Braun, G. B. Sukhorukov: ‘Nanorods as wavelength-selective

absorption centers in the visible and near-infrared regions of the

electromagnetic spectrum’, Adv. Mater., 2008, 20, (3), 506–510.

210. S. Erokhina, L. Benassi, P. Bianchini, A. Diaspro, V. Erokhin,

M. P. Fontana: ‘Light-driven release from polymeric microcap-

sules functionalized with bacteriorhodopsin’, J. Am. Chem. Soc.,

2009, 131, 9800–9804.

211. M. F. Bedard, S. Sadasivan, G. B. Sukhorukov, A. Skirtach:

‘Assembling polyelectrolytes and porphyrins into hollow capsules

with laser-responsive oxidative properties’, J. Mater. Chem., 2009,

19, (15), 2226–2233.

212. K. A. D. Gregersen, Z. B. Hill, J. C. Gadd, B. S. Fujimoto, D. J.

Maly, D. T. Chiu: ‘Intracellular delivery of bioactive molecules

using light-addressable nanocapsules’, ACS Nano, 2010, 4, (12),

7603–7611.

213. R. Palankar, A. G. Skirtach, O. Kreft, M. Bedard, M, Garstka,

K. Gould, H. Moehwald, G. B. Sukhorukov, M. Winterhalter,

S. Springer: ‘Controlled intracellular release of peptides from

microcapsules enhances antigen presentation on MHC Class I

molecules’, Small, 2009, 5, (19), 2168–2176.

214. A. M. Pavlov, A. V. Sapelkin, X. Y. Huang, K. M. Y. P’ng, A. J.

Bushby, G. B. Sukhorukov, A. G. Skirtach: ‘Neuron cells uptake

of polymeric microcapsules and subsequent intracellular release’,

Macromol. Biosci., 2011, 11, (6), 848–854.

215. S. J. Shu, X. G. Zhang, Z. M. Wu, Z. Wang, C. X. Li: ‘Gradient

cross-linked biodegradable polyelectrolyte nanocapsules for intra-

cellular protein drug delivery’, Biomaterials, 2010, 31, (23) 6039–

6049.

216. L. Y. Zakharova, A. R. Ibragimova, E. A. Vasilieva, A. B.

Mirgorodskaya, E. I. Yackevich, I. R. Nizameev, M. K. Kadirov,

Y. F. Zuev, A. I. Konovalov: ‘Polyelectrolyte capsules with

tunable shell behavior fabricated by the simple layer-by-layer

technique for the control of the release and reactivity of small

guests’, J. Phys. Chem. C, 2012, 116, (35), 18865–18872.

217. I. Marchenko, A. Yashchenok, T. Borodina, T. Bukreeva,

M. Konrad, H. Moehwald, A. Skirtach: ‘Controlled enzyme-

catalyzed degradation of polymeric capsules templated on

CaCO3: influence of the number of LbL layers, conditions of

degradation, and disassembly of multicompartments’,

J. Controlled Release, 2012, 162, (3), 599–605.

218. a) S. C. Balmert, S. R. Little: ‘Biomimetic delivery with micro-

and nanoparticles’, Adv. Mater., 2012, 24(28), 3757–3778. b) K.

Radhakrishnan, A. M. Raichur: ‘Biologically triggered exploding

protein based microcapsules for drug delivery’, Chem. Commun.,

2012, 48, (17), 2307–2309.

219. a) L. Pastorino, S. Erokhina, F. Caneva Soumetz, P. Bianchini,

O. Konovalov, A. Diaspro, C. Ruggiero, V. Erokhin: ‘Collagen

containing microcapsules: smart containers for disease controlled

therapy’, J. Colloid Interface Sci., 2011, 357, 56–62. b) S. Erokhina,

O. Konovalov, P. Bianchini, A. Diaspro, C. Ruggiero, V. Erokhin,

L. Pastorino: ‘Release kinetics of gold nanoparticles from collagen

microcapsules by total reflection X-ray fluorescence’, Colloids

Surf., A, 2013, 417, 83–88.




http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fbm049254t&isi=000229138900043

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fb609934c&isi=000244738900003


http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fja903066s&isi=000268399800041

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fc2tb00319h

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fjp065635k&isi=000245005300011








http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fb818774f&isi=000264745300019

http://www.maneyonline.com/action/showLinks?crossref=10.1117%2F1.429919&isi=000082183900007

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fjp045070x&isi=000227108800080

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fb715392a



http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fja8027636&isi=000258792000005


http://www.maneyonline.com/action/showLinks?crossref=10.1002%2Fadma.200400920

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fla047629q&isi=000227193500059


http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fnn102345f&isi=000285449100071


http://www.maneyonline.com/action/showLinks?crossref=10.1140%2Fepje%2Fi2003-10056-0&isi=000186890500003

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fjp305660c&isi=000308339600037


http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fc002564j&isi=000277031300006

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fam900784a

http://www.maneyonline.com/action/showLinks?crossref=10.1002%2Fsmll.200900809&isi=000271175700007

220. V. H. Orozco, V. Kozlovskaya, E. Kharlampieva, B. L. Lopez,

V. V. Tsukruk: ‘Biodegradable self-reporting nanocomposite films

of poly(lactic acid) nanoparticles engineered by layer-by-layer

assembly’, Polymer, 2010, 51, (18), 4127–4139.

221. Y. Itoh, M. Matsusaki, T. Kida, M. Akashi, Enzyme-responsive

release of encapsulated proteins from biodegradable hollow

capsules’, Biomacromolecules, 2006, 7, (10), 2715–2718.

222. V. Bocharova, O. Zavalov, K. MacVittie, M. A. Arugula, N. V.

Guz, M. E. Dokukin, J. Halamek, I. Sokolov, V. Privman,

E. Katz: ‘A biochemical logic approach to biomarker-activated

drug release’, J. Mater Chem., 2012, 22, (37), 19709–19717.

223. A. N. Zelikin, J. F. Quinn, F. Caruso: ‘Disulfide cross-linked

polymer capsules: en route to biodeconstructible systems’,


224. a) Q. He, Y. Cui, J. B. Li: ‘Molecular assembly and application of

biomimetic microcapsules’, Chem. Soc. Rev., 2009, 38, (8), 2292–

2303. b) W. Tong, X. Song, C. Gao: ‘Layer-by-layer assembly of

microcapsules and their biomedical applications’, Chem. Soc.

Rev., 2012, 41, (18), 6103–6124.

225. S. Z. Razzacki, P. K. Thwar, M. Yang, V. M. Ugaz, M. A. Burns:

‘Integrated microsystems for controlled drug delivery’, Adv. Drug

Delivery Rev., 2004, 56, (2), 185–198.

226. A. C. R. Grayson, R. S. Shawgo, Y. Li, M. J. Cima: ‘Electronic

MEMS for triggered delivery’, Adv. Drug Delivery Rev., 2004, 56,

(2), 173–184.

227. J. T. Santini, M. J. Cima, R. Langer: ‘A controlled-release

microchip’, Nature, 1999, 397, (6717), 335–338.

228. M. Hu, T. Lindemann, T. Gottsche, J. Kohnle, R. Zengerle,

P. Koltay: ‘Discrete chemical release from a microfluidic chip’,

J. Microelectromech Syst.. 2007, 16, (4), 786–794.

229. M. V. Kiryukhin, S. M. Man, A. V. Sadovoy, H. Y. Low, G. B.

Sukhorukov: ‘Peculiarities of polyelectrolyte multilayer assembly

on patterned surfaces’, Langmuir, 2011, 27, (13), 8430–8436.

230. M. V. Kiryukhin, S. R. Gorelik, S. M. Man, G. S. Subramanian,

M. N. Antipina, H. Y. Low, G. B. Sukhorukov: ‘Individually

addressable patterned multilayer microchambers for site-specific

release-on-demand’, Macromol. Rapid Commun. 2013, 34, (1), 87–93.

231. R. J. Jackman, D. C. Duffy, E. Ostuny, N. D. Willmore, G. M.

Whitesides: ‘Fabricating large arrays of microwells with arbitrary

dimensions and filling them using discontinuous dewetting’, Anal.

Chem. 1998, 70, (11), 2280–2287.

232. Y. Yin, Y. Xia: ‘Self-assembly of monodispersed spherical colloids

into complex aggregates with well-defined sizes, shapes, and

structures’, Adv. Mater. 2001, 13, (4), 267–271.

233. M. V. Kiryukhin, S. M. Man, A. Tonoyan, H. Y. Low, G. B.

Sukhorukov: ‘Adhesion of polyelectrolyte multilayers: sealing and

transfer of microchamber arrays’, Langmuir, 2012, 28, (13), 5678–

5686.

234. C. Gao, E. Donath, S. Moya, V. Dudnik, H. Mohwald: ‘Elasticity

of hollow polyelectrolyte capsules prepared by the layer-by-layer

technique’, Eur. Phys. J. E, 2001, 5, (1), 21–27.

235. A. J. Nolte, M. F. Rubner, R. E. Cohen: ‘Determining the

Young’s modulus of polyelectrolyte multilayer films via stress-

induced mechanical buckling instabilities’, Macromolecules, 2005,

38, (13), 5367–5370.

236. A. G. Skirtach, C. Dejugnat, D. Braun, A. S. Susha, A. L.

Rogach, W. J. Parak, H. Moehwald, G. B. Sukhorukov: ‘The role

of metal nanoparticles in remote release of encapsulated

materials’, Nano Lett. 2005, 5, (7), 1371–1377.

237. D. V. Volodkin, N. Madaboosi, J. Blacklock, A. G. Skirtach,

H. Moehwald: ‘Surface-supported multilayers decorated with bio-

active material aimed at light-triggered drug delivery’, Langmuir,

2009, 25, (24), 14037–14043.

238. A. Sadovoy, M. V. Lomova, M. N. Antipina, N. A. Braun, G. B.

Sukhorukov, M. Kiryukhin: ‘Layer-by-layer assembled multilayer

shells for encapsulation and release of fragrance’, ACS Appl.

Mater. Interfaces, 2013, 5, (18), 8948–8954.

239. R. H. Xiong, S. J. Soenen, K. Braeckmans, A. G. Skirtach:

‘Towards theranostic multicompartment microcapsules: In situ

diagnostics and laser-induced treatment’, Theranostics, 2013, 3,

(3), 141–151.



http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fam401871u

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fac971295a&isi=000073981600018

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fb816475b&isi=000268184600012

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fma0507950&isi=000230023400004

http://www.maneyonline.com/action/showLinks?crossref=10.1109%2FJMEMS.2007.892911&isi=000248578700002

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fbm060289y&isi=000241106600003

http://www.maneyonline.com/action/showLinks?crossref=10.7150%2Fthno.5846

http://www.maneyonline.com/action/showLinks?crossref=10.1002%2F1521-4095%28200102%2913%3A4%3C267%3A%3AAID-ADMA267%3E3.0.CO%3B2-9&isi=000167413000009


http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fnl050693n&isi=000230571300033

http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fla200939p&isi=000292124000060

http://www.maneyonline.com/action/showLinks?crossref=10.1039%2Fc2jm32966b&isi=000308099900046





http://www.maneyonline.com/action/showLinks?crossref=10.1021%2Fbm050832v&isi=000234549100007

http://www.maneyonline.com/action/showLinks?crossref=10.1007%2Fs101890170083&isi=000168942400004


http://www.maneyonline.com/action/showLinks?crossref=10.1016%2Fj.polymer.2010.06.060&isi=000281052100014

Documents

Micropackaging via layer-by-layer assembly: microcapsules and microchamber arrays