Rapid Synthesis of Superabsorbent Smart-Swelling Bacterial

Hindawi Publishing CorporationInternational Journal of Polymer ScienceVolume 2013 Article ID 905471 10 pageshttpdxdoiorg1011552013905471

Research ArticleRapid Synthesis of Superabsorbent Smart-Swelling BacterialCelluloseAcrylamide-Based Hydrogels for Drug Delivery

Manisha Pandey Mohd Cairul Iqbal Mohd AminNaveed Ahmad and Muhammad Mustafa Abeer

Centre for Drug Delivery Research Faculty of Pharmacy Universiti Kebangsaan Malaysia Jalan Raja Muda Abdul Aziz50300 Kuala Lumpur Malaysia

Correspondence should be addressed to Mohd Cairul Iqbal Mohd Amin mciaminyahoocouk

Received 9 May 2013 Revised 19 July 2013 Accepted 23 July 2013

Academic Editor Yulin Deng

Copyright copy 2013 Manisha Pandey et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

This study evaluated the effect of solubilized and dispersed bacterial cellulose (BC) on the physicochemical characteristics and drugrelease profile of hydrogels synthesized using biopolymers Superabsorbent hydrogels were synthesized by graft polymerization ofacrylamide on BC solubilized in an NaOHurea solvent system and on dispersed BC by using 1198731198731015840-methylenebisacrylamide asa crosslinker under microwave irradiation Fourier transform infrared spectroscopy analysis of the resulting hydrogels confirmedthe grafting and an X-ray diffraction pattern showed a decrease in the crystallinity of BC after the grafting process The hydrogelsexhibited pH and ionic responsive swelling behavior with hydrogels prepared using solubilized BC (SH) having higher swellingratios Furthermore compared to the hydrogels synthesized using dispersed BC the hydrogels synthesized using solubilized BCshowed higher porosity drug loading efficiency and release These results suggest the superiority of the hydrogels prepared usingsolubilized BC and that they should be explored further for oral drug delivery

1 Introduction

Currently natural polymers are being extensively exploredfor the fabrication of hydrogels owing to their biodegrad-ability biocompatibility nontoxicity and availability Conse-quently considerable attention has been given to bacterialcellulose (BC) a natural polymer because of its highmechan-ical strength thermal stability biocompatibility and purity[1] However its application in the synthesis of hydrogels islimited by its insolubility in common solvents owing to stronginter- and intramolecular hydrogen bonding Thus solubi-lization of BC in appropriate solvents could extend its appli-cation in the fabrication of films hydrogels and membranesand improve its purity and mechanical strength for pharma-ceutical and biomedical applications Although this macro-molecule has been successfully solubilized in lithium chlo-rideNN-dimethylacetamide [2] and N-methylmorpholine-N-oxide monohydrate [3] its use is limited to laboratory-scale operation because it is highly toxic To overcome this

challenge a sodium hydroxide (NaOH) complex solventwas prepared Cellulose with a low degree of polymeriza-tion (DP lt 300) has been reported to easily dissolve inNaOH (7ndash10wv) at low temperatures (minus5∘C to minus15∘C) [4]Conversely cellulose with a high degree of polymerization(DP gt 300) has been found not to be easily dissolve in NaOHsolution alone [5] The degree of polymerization of BC isin the range of 2000 and 6000 [6] but in some cases itreaches even 16000 to 20000 [7] So a combination of ureaand thiourea with NaOH has been shown to improve thedissolution of BC [8]

The applications of BC in hydrogel synthesis have beenlimited by its low absorptive ability due to the formation ofstrong intra- and interhydrogen bonds after drying Howeverformation of a double-network structure by combining BCwith other polymers (gelatin and chitosan) [9 10] or graftcopolymerization [11ndash14] has been shown to overcome theproblem Graft copolymerization of BC is mainly performedby free radical polymerization [15] and ionizing radiation

2 International Journal of Polymer Science

[13 14] Accelerated microwave irradiation has gained a lot ofattention because of the following factors associated with itsafety concerns low energy consumption and low produc-tion cost [16 17] Compared to hydrogels synthesized usingwater bath method hydrogels synthesized using microwaveirradiation have greater porosity (005ndash015 times 10minus2 cm3gversus 045ndash27 times 10minus2 cm3g) [18] Furthermore Kumar et alreported that the percentage of grafting of xanthan gum withpolyacrylamide (PAM) increased from 1276 to 8715 withan increase in irradiation power from 40 W to 100 W conse-quentially increasing the drug release rate with an increase ingrafting percentageThey also observed a higher drug releaserate from the grafted copolymer matrix as compared to thexanthan gum matrix [19]

Over the last twodecades ldquosmart-swelling hydrogelsrdquo thatexhibit remarkable changes in their swelling behavior inresponse to environmental stimuli such as temperaturepH and ionic strength have become popular carriers forcontrolled drug delivery PAM which was used in this studyhas been reported to produce nonionic hydrogels Howeverin the presence of an alkali PAM is hydrolyzed and producesanionic hydrogels that exhibit higher pH sensitivity thanthat of nonionic hydrogels Electrostatic repulsion betweenthe carboxylic groups of the ionic hydrogels results in apH-responsive swelling of the hydrogel such pH-responsiveswelling behavior can assist in the control of drug release[11 20ndash23]

In this study BCPAM hydrogels were synthesized usingBC dispersion and BC dissolved in NaOHurea solvent sys-tem Hydrogels were developed by using microwave irradia-tion instead of the conventional heating method to improvethe degree of grafting and reduce the time consumption Theresulting hydrogels were characterized using Fourier trans-form infrared spectroscopy (FT-IR) X-ray diffraction (XRD)and scanning electron microscopy (SEM) The swellingbehavior of the hydrogels was then determined at differentpH values and ionic strengths Finally drug loading andrelease behavior of the hydrogels were investigated to evaluatethe potential for the application of these hydrogels in drugdelivery

2 Experimental

21 Materials Acrylamide (AM) potassium persulfate(KPS) NN1015840-methylenebisacrylamide (MBA) and theophyl-linewere purchased fromSigmaAldrich JapanUrea sodiumhydroxide and other reagents were of analytical grade andused without further purification Phosphate buffer solutionsat pH 2 5 7 and 9 were prepared as described in the BritishPharmacopoeia Nata de coco was used as a source of BCand was procured from a local food company

22 Purification of Nata de Coco Nata de coco was purifiedas previously described [1] Briefly nata de coco was washedand soaked in distilled water to attain pH (5ndash7) To achievea constant weight the samples were then blended in a wetblender poured into trays and then freeze-dried Using apulverizer (Pulverisette 14 Frisch Germany) the BC sheetswere micronized to produce a fluffy BC powder

23 Synthesis of Hydrogels A solvent system consisting ofNaOHurea was used to dissolve the BC Two different ratiosof NaOH (6amp 8wv) and urea (4wv) were dissolved indistilled water to prepare the solvent system for dissolutionNext 25 g of BC powder was added to 100mL of solventwith constant stirring and stored at minus10∘C for 12 hThe frozensolid was then thawed and stirred extensively at 25∘C untila transparent solution was attained [24] To prepare the BCdispersion purified BC with a particle size in the range 50ndash100 120583mwas dispersed in distilledwater to produce 25 (wv)dispersion [25]

To synthesize the BCPAM hydrogels AM (20 g) wasadded to 20mL of freshly prepared BC solution followed bythe addition of potassium persulfate as an initiator (7wwof AM) and MBA (7ww of AM) as a crosslinker Nextthe reaction mixtures were irradiated using a microwaveirradiator (LG model MS2388K Korea) at 340W for 30 s tosynthesize hydrogels (SH) Similarly the hydrogels from thedispersed BC were produced using the same concentrationof AM crosslinker and initiator with the exception of BCdispersion being used instead of a solution (DH) SimilarlyPAM was prepared by exposure to microwave radiations inthe absence of BC as shown in Table 1

24 Characterization of the Hydrogels

241 Gel Fraction Determination The gel fractions (GF) ofthe hydrogels were determined to estimate the degree ofgrafting Freshly prepared hydrogel discs (12 cm in diameter)were dried in an oven at 60∘C to a constant weight (119882

0) The

dried hydrogel discs were then soaked in distilled water toremove any unreacted monomers or sol from the hydrogelsThe water was changed after 24 h and the absorbance of thesolvent used to soak the hydrogels was determined at 270 nmto detect the unreacted PAMThese extracted hydrogels werethen dried again to a constant weight (119882

1) at a temperature

of 60∘C in an ovenThe percentage of gel fraction (GF) wascalculated using (1) [13 14]

GF = 11988211198820

times 100 (1)

242 FT-IR Spectroscopic Analysis IR spectra of the sampleswere recorded using Perkin Elmer FT-IR Spectra 2000 atroom temperature (25∘C) The test specimens were preparedusing the KBr disc method and analyzed over the range of400ndash4000 cmminus1

243 X-Ray Diffraction X-ray diffractograms of the BC andhydrogels were obtained using an X-ray diffractometer (D8-Advance Bruker AXS) with Cu K120572 radiation at 40 kV and50mA in a differential angle range of 5ndash60∘ 2120579 [4]

244 Morphological Analysis Themorphology of the freeze-dried swollen hydrogels was examined using scanning-electron microscopy (Leo 1450 VP Germany) The freeze-dried samples were mounted on to an aluminum stub withdouble-sided carbon tape and coated with gold in a sputtercoater (SC500 BioRad UK) under argon atmosphere

International Journal of Polymer Science 3

Table 1 Formulation code gel fraction and release kinetics of hydrogel

Code BCAM ratio( wv)

NaOHurea ratio( wv)

Gel fraction() (mean plusmn SD)

Zero order (ghr) First order (hrminus1) Peppas1198772

119870 1198772

119870 1198772

119899

PAMDH

0102510

0000

8798 plusmn 2428209 plusmn 21

09960996

01000111

08440841

00020002

09570954

07940775

SH64

2510 64 7329 plusmn 165 0991 0135 0824 0002 0932 0723SH84

2510 84 695 plusmn 305 0990 0149 0813 0002 0921 0712

245 Mechanical Properties The mechanical properties ofthe hydrogels of similar dimensions (12 cm in diameter)were determinedusing Instron 5567Universal Testing Systemequipped with a load cellThemaximum force load was set to250N and the compression rate was 5mmmin Strain wasdetermined by measuring the peak of the curve while thecompressive modulus was calculated by measuring the slopeof the stress and strain curvesThe tests were repeated at least3 times [26]

25 Swelling Studies The smart swelling behavior of thehydrogels was investigated in buffer solutions at different pHvalues (2 5 7 and 9) and ionic strengths (05M 01M 001Mand 0001MNaCl) Dried hydrogel (Gd) with a knownweightwas immersed in 50mL of the swelling media The swollensamples were weighed (Gs) at fixed time intervals and theexcess media were removed by blotting with a piece of filterpaperThe percentage of swelling ratio ( SR) of the hydrogelwas calculated using (2)

SR =(Gs minus Gd)

Gdtimes 100 (2)

26 Drug Release Studies

261 Drug Loading Theophylline was loaded as a modeldrug into the hydrogels (PAMDH SH

64 and SH

84) by using

a diffusion partition method The dried hydrogel discs wereimmersed in 20mL of drug solution (10mgmL) at pH 74 for24 hThe swollen hydrogel discs were removed from the drugsolution washed with distilled water and dried at 30∘C toa constant weight The concentration of the drug remainingin the solution was determined by measuring the absorbanceat 272 nm by using spectrophotometry (UV-1601 ShimadzuJapan) The drug loading percentage (DL ) was calculatedusing (3)

DL =119882dg

119882gtimes 100 (3)

where119882dg is the amount of drug entrapped in the hydrogeland119882g is the weight of the dried hydrogel disc

262 In Vitro Drug Release Study Drug release studies fromhydrogels were conducted using a submerging theophylline-loaded hydrogel disc into 100mL of buffer solution at pH 74for up to 24 h The dissolution media were maintained at afixed temperature of 37∘C with constant agitation at 50 rpm

Aliquots of 4mL were withdrawn at specific time intervalsand the fluid stock was continuously replenished with freshmedia The concentration of the drug was then measuredusing a spectrophotometer at 272 nm

The drug release data for 8 h was fitted to a zero-orderfirst-order and Korsmeyer-Peppas equation to determine thetype of release kinetics of theophylline from the hydrogelsThe value of the release exponent of the Korsmeyer-Peppas(119899) equation was used to describe the release mechanism ofthe drug from the hydrogel [27]

3 Results and Discussion

31 Synthesis of the Hydrogels The main objective of thiswork was to investigate the effect of the physical state of theBC and solvents on the properties of hydrogels producedfrom it after irradiationwithmicrowave energyTheBCPAMhydrogels were successfully synthesized using the acceleratedmicrowave irradiationmethod bymaintaining the entire syn-thesis parameters constant except for the physical state of theBC which was either in a dispersed or solubilized form After96 h no residues from the AM were found in the extractionmedium suggesting that soaking the hydrogels for 4 days wassufficient to extract all the unreacted monomers

32 Reaction Mechanism The reaction mechanism involvedin the synthesis of the hydrogel is shown in Figure 1 In thefirst step sulfate ion radicals (SO

4

minus∙) were produced frompotassium persulfate because of microwave irradiationwhich further reacted with water molecules to generatehydroxyl radicals (OH∙) Moreover in DH hydrogels bothSO4

minus∙ and OH∙ radicals reacted with AM and BC to produceactive sites for the reaction Activated monomers that poly-merized and produced PAM chains were then grafted intothe BC at the active sites to produce a grafted BCPAM PAMand the grafted polymers were further cross-linked by MBAto produce the hydrogel

Similarly in hydrogels that were produced from solubi-lized BC (SHs) the active sites were generated due to thepresence of hydroxyl radicals (OH∙) and sulfate ion radicals(SO4

minus∙) The activated monomers were polymerized andgrafted into the BC backbone and finally cross-linked byMBA The only difference in the reaction mechanism of theSHwas the partial hydrolysis of AM to sodium acrylate in thepresence of NaOHTherefore the finally synthesized productcould also be designated as BC-g-poly (AM-sodium acrylate)hydrogel whichwas anionic in nature because of the presenceof the carboxylate anion [11]


Microwave

Free radical formation

NaOH Hydrolysis

+

+

Polymerization and grafting

Grafted polymer Crosslinking

MBA

BC-g-poly(acrylamide-sodium acrylate) hydrogel

BC

(Sodium acrylate)

Initiation

Steps involved in synthesis of DH hydrogelsSteps involved in synthesis of SH hydrogelsSteps involved in synthesis of both hydrogels

S2O8

O

O

OOO

O

O

OH

NH2

NH2NH2

ONa

ONa

(AM)

(AM)

2SO4

minus

Figure 1 Reaction mechanism of hydrogel synthesis

33 Gel Fractions The fundamental characteristic of hydro-gels is their ability to imbibe and hold a large amount ofwater while remaining insoluble The gel fraction of thehydrogels indicates the degree of grafting and cross-linking inthe hydrogels The cross-linking prevents the hydrogels fromsolubilizing and only enables the expansion of the hydrogelduring the extraction thus a higher GF indicates a higherdegree of cross-linking The gel fractions of the hydrogelsprepared from solubilized BC (SH

64and SH

84) dispersed

BC (DH) and pure PAMwere 7329plusmn165 695plusmn305 8209plusmn21 and 8798 plusmn 242 respectively (Table 1) The extractedweights of SH

64and SH

84were comparatively lower than

those of the DH and PAM hydrogels This phenomenoncould be attributed to NaOH which may have weakened thecross-linking points resulting in a decrease in cross-linkingdensity and consequently the gel fraction At higher NaOHconcentrations the polymeric chains were well separatedcausing higher sol content This may also partially be dueto weight loss during weighing owing to the fragile natureof the hydrogel at equilibrium swelling However the DHand PAM hydrogels exhibited a higher gel fraction percent-age throughout the extraction process Marandi et al havereported similar observations when pure PAM hydrogelswere hydrolyzed using NaOH [20] However the gel fractionof the BCPAM hydrogels containing solubilized BC couldbe further improved by changing the concentration of theinitiator and cross-linker as well as themicrowave irradiationpower

34 FT-IR Spectroscopic Analysis The FT-IR spectra of pureBC PAM DH SH

64 and SH

84are presented in Figure 2

In the pure BC spectra peaks at 1059 cmminus1 1163 cmminus12914 cmminus1 and 3398 cmminus1 represented CndashO stretching vibra-tion CndashOndashC stretching of the ether linkage (14-120573-d-glu-coside) CndashH stretching and OndashH stretching of the inter-molecular hydrogen bonds respectively [14] However thePAM spectra exhibited distinct peaks at 3421 and 3215 cmminus1representing NndashH asymmetric and symmetric stretchingvibrations at 1658 and 1451 cmminus1 which corresponded to theC=O stretching of the amide I band and CndashN stretchingrespectively [28] The spectra of DH and SH confirmedthe presence of PAM with an absorption band at 1655 and1667 cmminus1 due to C=O stretching 1452 cmminus1 due to CndashNstretching and a broad absorption band at 3438 cmminus1 due tooverlapping OndashH stretching of the BC and NndashH stretchingof AM The strong absorption band at 2924 and 2929 cmminus1can be attributed to an overlap of CndashH stretching of theBC and AM in the absence of CndashO stretching vibrations at1059 cmminus1 in theDH and SHhydrogels spectra indicating thegrafting of PAM onto the BC The spectra of SH

64and SH

84

indicated appearance of a new absorbance band at 1568 cmminus1which was assigned to the asymmetric stretching of thecarboxylate anion indicating partial hydrolysis of the amidegroup into a carboxylate group and production of ammoniaThe hydrolysis was further confirmed by the appearanceof another sharp peak at 1408 cmminus1 which was attributed


BC

PAM

DH

3421 1658

1451

1667

2929 15681408

3398

2914

1163

1059

3215

3438

2924

1452

SH64

SH84

4000 3500 3000 2500 2000 1500 1000 500400(cmminus1)

T(

)

Figure 2 FT-IR spectra of bacterial cellulose (BC) polyacrylamide hydrogel (PAM) and BCAM hydrogels

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

Lin

(cou

nts)

Lin

(cou

nts)

6 10 20 30 40 50 60

2120579 scale

0123456789

1011121314151617181920212223242526times10

4

6 10 20 30 40 50 60 702120579 scale

BCPAMDH

SH64

SH84

Figure 3 FIGURE 3 X-ray diffractogram of pure bacterial cellulose polyacrylamide hydrogel and BCAM hydrogels

to the symmetric stretching mode of the carboxylate anion[20 29]

35 X-Ray Diffraction Study The X-ray diffraction patternof PAM DH SH

64 and SH

84indicated that the hydrogels

exhibited a more amorphous morphology compared to thatof pure BC The diffractogram of pure BC showed a similar

pattern with 4 characteristic peaks of cellulose I located at2120579 = 14∘ 16∘ 23∘ and 34∘ which corresponded to (1 0 1)(1 0 1) (0 0 2) and (0 4 0) crystallographic planerespectively [30] As depicted in Figure 3 the characteristicdiffraction at 2120579 = 2248∘ in the DH 2202∘ in SH

64 and

SH84

hydrogels is assigned to the cellulose crystal howeverthe peak intensity of the cellulose was reduced in the SH


(a) (b)

(c) (d)

Figure 4 Scanning electron micrograph of (a) PAM (b) DH (c) SH64 and (d) SH

84

compared to DH which indicated a more amorphous natureof BC in the SH owing to the alkali treatment Comparison ofthe XRD pattern of BC with that of DH revealed decreasedcrystallinity in the BC when it was grafted with PAMThe disappearance of the characteristic pattern of peaks forcellulose in the DH and SH may be due to the cross-linkingbetween BC and PAM resulting in the destruction of theinitial crystalline arrangement of BC

36 Morphological Analysis Scanning electron micrographsof the freeze-dried swollen hydrogels are shown in Figure 4SH64

and SH84

exhibited relatively higher porosity thanthat of DH and PAM The SEM images of SH

64and SH

84

demonstrated a well-defined interconnected three-dimen-sional porous network structure while the surface pores weremuch smaller in DH Interestingly the surfaces of both SHswere fluffier and exhibited larger and smaller interconnectedpores compared to those of DH and PAM These highlyinterconnected pores provided more available regions forthe diffusion of water molecules and thus the hydrogel maydemonstrate a higher water absorption capacity [14] Thehigh-porosity structure of the SH was attributed to the

electrostatic repulsion resulting from the carboxylate anion(ndashCOOminus) group which was produced as a result of the partialhydrolysis of AM as previously discussed NaOH is alsoresponsible for the weakening of the hydrogel by attackingthe crosslinking points of polyacrylamide and as a result thecrosslink density decreases The decrease in crosslink densitycauses the high swelling capacity of the hydrogel This obser-vation also supported the proposed reaction mechanism inwhich the production of ammonia gas during the synthesisprocess in the presence of NaOH led to the formation of amore porous hydrogelThe amount of ammonia gas liberatedwas proportional to the alkali concentration [20] whichresulted in a more porous surface and spongy appearance inSH84 as shown in Figure 4

37 Mechanical Test Themechanical properties of PAM andBCPAMhydrogels (DH and SH

64) weremeasured in hydro-

gels with a 500 swelling and equilibrium swelling ratioDue to the highly fragile nature of SH

84 it was not used to

study themechanical strength of these hydrogelsWhen thesehydrogels (at 500 swelling) were subjected to a compressiveforce they were nonbreakable although some fractures were


0

500

1000

1500

2000

2500

3000

2 5 7 9

Swel

ling

ratio

()

pH

PAMDH

SH64

SH84

(a)

PAMDH

0

500

1000

1500

2000

2500

3000

05 M 01 M 001 M 0001 M

Swel

ling

ratio

()

Salt concentration (mole)

SH64

SH84

(b)

Figure 5 Swelling behavior of hydrogels at different (a) pH and (b) ionic strength

Table 2 Mechanical properties of hydrogels (119899 = 3)

Formulation

Compressivestress(MPa)

(mean plusmn SD)

Compressivestrain

(mmmm)(mean plusmn SD)

Compressivemodulus(MPa)

(mean plusmn SD)PAMa 0434 plusmn 0038 1685 plusmn 0083 1592 plusmn 0069DHa 0265 plusmn 0025 1961 plusmn 0012 1449 plusmn 0079SH64

a 0410 plusmn 0053 1359 plusmn 0074 1172 plusmn 0056PAMb 0562 plusmn 0067 1608 plusmn 0087 1237 plusmn 0082DHb 0407 plusmn 0031 1464 plusmn 0013 0722 plusmn 0026SH64

b 0304 plusmn 0029 1636 plusmn 0093 0229 plusmn 0014aCompression test of hydrogel with 500 swelling ratiobCompression test of hydrogel with equilibrium swelling ratio

observed on the surface of the hydrogels Conversely whencompressive force was applied on the hydrogels at equilib-rium swelling greater fracturing was observed in PAM andDH while SH

64hydrogels were completely crushed due to

the lack of efficient energy dissipation and irregular distri-bution of cross-linking points The Youngrsquos modulus valueswere 1592 1449 and 1172 for PAMDH and SH

64hydrogels

respectively as shown in Table 2 At 500 swelling theYoungrsquos modulus values for PAM and DH hydrogels werecomparable but at swelling equilibrium it increased in theorder of SH

64lt DH lt PAM as shown in Table 2 These data

revealed that the PAM hydrogel was comparatively moreelastic (less rigid) compared to the bicomponent (BCPAM)hydrogels XRD data also supported this finding where thebicomponent (BCPAM) hydrogels were more crystalline(rigid) than polyacrylamide Comparing the mechanicalstrength at 500 and equilibrium swelling of the hydrogelsrevealed that hydrogels with a higher water content showedlower mechanical strength because of the reduction in poly-meric content per unit volume corresponding to an increase

in swellingTheYoungrsquos modulus values of DH and SH64

alsoindicated that grafting of nonionic PAM with BC resultedin a greater mechanical strength than that of anionic PAMThis could be due to a variation in cross-linking density innonionic and anionic polymers

38 Swelling Studies

381 pH Response The hydrogels were allowed to swell in50mL of swelling media at different pHs and the percentageswelling ratio ( SR) at 24 h is shown in Figure 5(a) Thehydrogels exhibited the highest SR at pH 7 (Figure 5(a))The SR of the SH

64and SH

84hydrogels at pH 7 (237747plusmn

6592 and 259562 plusmn 8536 resp) was approximately 27ndash30 times higher than the DH hydrogels (88467 plusmn 4518)and 36ndash40 times higher than the PAM hydrogels (6645 plusmn3446)The percentage of swelling of the hydrogel was mainlygoverned by the polarity of the formulations which wasdependent on the nature of the polymers the concentrationof the cross-linking agent and the reaction conditions Inthis study the composition of the hydrogels and the reactionconditions remained constant and thus the degree of swellingwas mainly controlled by the nature of the polymers and thesolvent ratio for the dissolution of the BC Previous studiessuggested that the swelling of raw BC (cubes) is nearlyirreversible after drying or compression but it can be maderepeatedly swollen by grafting with AM [9 15 26] Theswelling percentage of DH SH

64and SH

84clearly underlie

the effect of the solubility and solvent concentration on theswelling of BC hydrogels Jin et al reported that this solventsystem has the capability of breaking hydrogen bonds pre-venting the reassociation of cellulose macromolecules andchanging the highly crystalline form of cellulose into anamorphous form resulting in remarkable changes in theswelling of the hydrogels [31] This high pH which is respon-sible for swelling is mainly attributed to the hydrolysis of


the ndashCONH2group of the PAM to the ndashCOONa group in the

presence of NaOH Electrostatic repulsion between ndashCOOminusions creates more spaces within the hydrogel matrix whichimbibes a large amount of water [32]

The SRwas observed at different pH values to study thepH sensitivity of the hydrogels The swelling of the hydrogelsincreased with increasing pH (from 2 to 7) but decreased atpH 9 as shown in Figure 5(a) The order of the pH sensitivityof the hydrogels was SH

84gt SH64gt DH gt PAM inde-

pendent of sensitivity that is specific to acidic or basic pHThe sharp change in swelling in SH was most likely dueto the protonation and deprotonation of the ndashCOOminus groupresulting from the partial hydrolysis of PAM at a lower andhigher pH [33] In contrast the PAM andDH both containednonionic PAMs which one unable to ionize in an aqueoussolution but would undergo hydrolysis in acidic and basicsolutions to produce the protonated amino (minusNH

3

+) and

carboxylic acids (COOminus) groups

382 Ionic Strength Response The swelling behavior of thehydrogels at different NaCl concentrations is presented inFigure 5(b) As evident from the graph the ionic strength wasinversely proportional to the SR This may be attributed toa change in osmotic pressure and a reduction in the repulsiveforces at a higher ionic strength The difference in osmoticpressure between water and the hydrogel was greater thanthe osmotic pressure difference between the salt solution andhydrogel Thus the swelling of the hydrogel in water wasmuch higher than that in an ionic solution The presenceof salt reduces the osmotic pressure difference of the saltsolution [20] The lower swelling at a higher ionic strengthcould also be explained due to the neutralization of the car-boxylate anions in the presence of Na+ resulting in decreasedelectrostatic repulsive forces which was a controlling factorfor swelling [14]

39 Drug Release Studies The DL of PAM DH SH64 and

SH84

was 3378 plusmn 285 4132 plusmn 195 5846 plusmn 335and 7456 plusmn 321 respectively This indicates that drugloading is dependent on the porosity and swelling propertiesof the hydrogels Similarly the in vitro release profile ofthe formulations primarily is dependent on the interactionsof the drug with the polymeric network solubility of thedrug and swelling of the hydrogel in the dissolution mediaAs shown in Figure 6 SH showed a higher cumulativepercentage release in phosphate buffer (pH 74) for 8 h thanthat shown by DH and PAM A similar pattern was observedin the total cumulative release which was attributed to theswelling behavior of the hydrogels Comparison of SH

64and

SH84

revealed that SH64

showed a lower release which wasattributed to the higher swelling and porosity in SH

84 The

release pattern of all of the hydrogels was biphasic firstbecause of the burst release due to the presence of the drugon the surface of the hydrogels which was followed by asustained release An initial rapid release may be caused bythe higher concentration gradient that acts as the drivingforce for the drug release followed by a reduction in therelease rate whichmay be due to the thickness of the hydrogelacting as a diffusion barrier

0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500

Cum

ulat

ive r

elea

se (

)

Time (min)

PAMDH

SH64

SH84

Figure 6 In vitro drug release profile of hydrogels in buffer pH 74

The release data of the hydrogels in PBS (pH 74) werebest fitted to zero-order release kinetics as shown in Table 1In addition the release exponent of Korsmeyer-Peppas (119899) ofall of the formulations was in the range of 045ndash089 whichindicated non-Fickian diffusion The value of 119899 indicatedconcurrent absorption of the dissolution media and releaseof the model drug which resulted in drug release

4 Conclusions

In this study the accelerated microwave irradiation methodwas successfully used to synthesize hydrogels fromBCdisper-sion and BC solution in a NaOHurea aqueous system withPAM by using MBA as a cross-linker These results suggestedthat the hydrogel containing cellulose in an NaOHurea solu-tion showed more uniform porosity structure distributionthe highest swelling property and a higher sensitivity towardspH and ionic solution compared to that of DH and PAMThese drug release experiments revealed that SH hydrogelsexhibited a higher drug loading capacity and higher drugrelease From these results it can be concluded that the SHsexhibited superior properties for drug delivery applicationThe pH sensitivity and superabsorbent response suggestedthat these smart hydrogels could be further explored forcontrolled oral delivery of protein peptides and acid-labiledrugs However further studies are warranted to overcomethe fragility and improve the mechanical properties of thesehydrogels

Acknowledgments

The authors would like to thank the Ministry of HigherEducation (MOHE) and the Ministry of Agriculture (MoA)Malaysia for their support This project was funded byMoA Science fund 05-01-02-SF1023 and UKM-Farmasi-02-FRGS0192-2010


References

[1] A G Abadi M C I M Amin N Ahmad H Katas and J AJamal ldquoBacterial cellulose film coating as drug delivery systemphysicochemical thermal and drug release propertiesrdquo SainsMalaysiana vol 41 no 5 pp 561ndash568 2012

[2] C L McCormick P A Callais and B H Hutchinson Jr ldquoSolu-tion studies of cellulose in lithium chloride and NN-dimethy-lacetamiderdquoMacromolecules vol 18 no 12 pp 2394ndash2401 1985

[3] D Klemm BHeublein H P Fink andA Bohn ldquoCellulose fas-cinating biopolymer and sustainable rawmaterialrdquoAngewandteChemiemdashInternational Edition vol 44 no 22 pp 3358ndash33932005

[4] M Egal T Budtova and P Navard ldquoStructure of aqueous solu-tions ofmicrocrystalline cellulosesodiumhydroxide below 0∘Cand the limit of cellulose dissolutionrdquoBiomacromolecules vol 8no 7 pp 2282ndash2287 2007

[5] J Cai and L Zhang ldquoRapid dissolution of cellulose in LiOHurea and NaOHurea aqueous solutionsrdquo Macromolecular Bio-science vol 5 no 6 pp 539ndash548 2005

[6] R Jonas and L F Farah ldquoProduction and application of micro-bial celluloserdquo Polymer Degradation and Stability vol 59 no 1ndash3 pp 101ndash106 1998

[7] K Watanabe M Tabuchi Y Morinaga and F YoshinagaldquoStructural features and properties of bacterial cellulose pro-duced in agitated culturerdquo Cellulose vol 5 no 3 pp 187ndash2001998

[8] S Zhang F X Li J Yu and Y L Hsieh ldquoDissolution behaviourand solubility of cellulose in NaOH complex solutionrdquo Carbo-hydrate Polymers vol 81 no 3 pp 668ndash674 2010

[9] A Nakayama A Kakugo J P Gong et al ldquoHigh mechanicalstrength double-network hydrogel with bacterial celluloserdquoAdvanced Functional Materials vol 14 no 11 pp 1124ndash11282004

[10] J Kim Z Cai H S Lee G S Choi D H Lee and C Jo ldquoPrepa-ration and characterization of a bacterial cellulosechitosancomposite for potential biomedical applicationrdquo Journal ofPolymer Research vol 18 no 4 pp 739ndash744 2011

[11] A L Buyanov I V Gofman L G Revelrsquoskaya A K Khripunovand A A Tkachenko ldquoAnisotropic swelling and mechanicalbehavior of composite bacterial cellulose-poly(acrylamide oracrylamide-sodium acrylate) hydrogelsrdquo Journal of theMechan-ical Behavior of Biomedical Materials vol 3 no 1 pp 102ndash1112010

[12] N Halib M C I M Amin I Ahmad Z M Hashim and NJamal ldquoSwelling of bacterial cellulose-acrylic acid hydrogelssensitivity towards external stimulirdquo Sains Malaysiana vol 38no 5 pp 785ndash791 2009

[13] M C I M Amin N Halib N Ahmad and I Ahmad ldquoSynthe-sis and characterization of thermo- and pH-responsive bacterialcelluloseacrylic acid hydrogels for drug deliveryrdquoCarbohydratePolymers vol 88 no 2 pp 465ndash473 2012

[14] N Halib M C I M Amin and I Ahmad ldquoUnique stimuliresponsive characteristics of electron beam synthesized bacte-rial celluloseacrylic acid compositerdquo Journal of Applied PolymerScience vol 116 no 5 pp 2920ndash2929 2010

[15] J Zhang J Rong W Li Z Lin and X Zhang ldquoPreparation andcharacterization of bacterial cellulosepolyacrylamide hydro-gelrdquo Acta Polymerica Sinica no 6 pp 602ndash607 2011

[16] Z Zhao Z Li Q Xia H Xi and Y Lin ldquoFast synthesis oftemperature-sensitive PNIPAAm hydrogels by microwave irra-diationrdquo European Polymer Journal vol 44 no 4 pp 1217ndash12242008

[17] J Jovanovic andBAdnadjevic ldquoInfluence ofmicrowave heatingon the kinetic of acrylic acid polymerization and crosslinkingrdquoJournal of Applied Polymer Science vol 116 no 1 pp 55ndash632010

[18] Z X Zhao Z Li Q B Xia E Bajalis H X Xi and Y S LinldquoSwellingdeswelling kinetics of PNIPAAm hydrogels synthe-sized by microwave irradiationrdquo Chemical Engineering Journalvol 142 no 3 pp 263ndash270 2008

[19] A Kumar K Singh and M Ahuja ldquoXanthan-g-poly(acrylam-ide)microwave-assisted synthesis characterization and in vitrorelease behaviorrdquoCarbohydrate Polymers vol 76 no 2 pp 261ndash267 2009

[20] G B Marandi K Esfandiari F Biranvand M Babapour SSadeh and G R Mahdavinia ldquoPH sensitivity and swellingbehavior of partially hydrolyzed formaldehyde-crosslinkedpoly(acrylamide) superabsorbent hydrogelsrdquo Journal of AppliedPolymer Science vol 109 no 2 pp 1083ndash1092 2008

[21] A Mohanan B Vishalakshi and S Ganesh ldquoSwelling and dif-fusion characteristics of stimuli-responsive N-isopropylacryl-amide and 120581-carrageenan semi-IPN hydrogelsrdquo InternationalJournal of Polymeric Materials vol 60 no 10 pp 787ndash798 2011

[22] Z Peng and F Chen ldquoSynthesis and properties of lignin-basedpolyurethane hydrogelsrdquo International Journal of PolymericMaterials vol 60 no 9 pp 674ndash683 2011

[23] Y M Mohan P S K Murthy H Sudhakar B V K Naidu KM Raju and M P Raju ldquoSwelling and diffusion properties ofpoly(acrylamide-co-maleic acid) hydrogels a study with dif-ferent crosslinking agentsrdquo International Journal of PolymericMaterials vol 55 no 11 pp 867ndash892 2006

[24] C Chang L Zhang J Zhou L Zhang and J F KennedyldquoStructure and properties of hydrogels prepared from cellulosein NaOHurea aqueous solutionsrdquo Carbohydrate Polymers vol82 no 1 pp 122ndash127 2010

[25] M Pandey and M C I M Amin ldquoAccelerated prepara-tion of novel bacterial celluloseacrylamide-based hydrogel bymicrowave irradiationrdquo International Journal of PolymericMaterials vol 62 no 7 pp 402ndash405 2013

[26] Y Hagiwara A Putra A Kakugo H Furukawa and J PGong ldquoLigament-like tough double-network hydrogel based onbacterial celluloserdquo Cellulose vol 17 no 1 pp 93ndash101 2010

[27] P L Ritger andN A Peppas ldquoA simple equation for descriptionof solute release II Fickian and anomalous release from swel-lable devicesrdquo Journal of Controlled Release vol 5 no 1 pp 37ndash42 1987

[28] C Ozeroglu and A Birdal ldquoSwelling properties of acrylamide-NN1015840-methylene bis(acrylamide) hydrogels synthesized byusing meso-23-dimercaptosuccinic acid-cerium(IV) redoxcouplerdquo Express Polymer Letters vol 3 no 3 pp 168ndash176 2009

[29] Y Song J Zhou L Zhang and X Wu ldquoHomogenous mod-ification of cellulose with acrylamide in NaOHurea aqueoussolutionsrdquoCarbohydrate Polymers vol 73 no 1 pp 18ndash25 2008

[30] S Ouajai and R A Shanks ldquoComposition structure and ther-mal degradation of hemp cellulose after chemical treatmentsrdquoPolymer Degradation and Stability vol 89 no 2 pp 327ndash3352005

[31] H Jin C Zha and L Gu ldquoDirect dissolution of cellulosein NaOHthioureaurea aqueous solutionrdquo Carbohydrate Re-search vol 342 no 6 pp 851ndash858 2007


[32] S Kim G Iyer A Nadarajah J M Frantz and A L SpongbergldquoPolyacrylamide hydrogel properties for horticultural applica-tionsrdquo International Journal of Polymer Analysis and Character-ization vol 15 no 5 pp 307ndash318 2010

[33] R da Silva and M G de Oliveira ldquoEffect of the cross-linkingdegree on the morphology of poly(NIPAAm-co-AAc) hydro-gelsrdquo Polymer vol 48 no 14 pp 4114ndash4122 2007

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


[13 14] Accelerated microwave irradiation has gained a lot ofattention because of the following factors associated with itsafety concerns low energy consumption and low produc-tion cost [16 17] Compared to hydrogels synthesized usingwater bath method hydrogels synthesized using microwaveirradiation have greater porosity (005ndash015 times 10minus2 cm3gversus 045ndash27 times 10minus2 cm3g) [18] Furthermore Kumar et alreported that the percentage of grafting of xanthan gum withpolyacrylamide (PAM) increased from 1276 to 8715 withan increase in irradiation power from 40 W to 100 W conse-quentially increasing the drug release rate with an increase ingrafting percentageThey also observed a higher drug releaserate from the grafted copolymer matrix as compared to thexanthan gum matrix [19]

Over the last twodecades ldquosmart-swelling hydrogelsrdquo thatexhibit remarkable changes in their swelling behavior inresponse to environmental stimuli such as temperaturepH and ionic strength have become popular carriers forcontrolled drug delivery PAM which was used in this studyhas been reported to produce nonionic hydrogels Howeverin the presence of an alkali PAM is hydrolyzed and producesanionic hydrogels that exhibit higher pH sensitivity thanthat of nonionic hydrogels Electrostatic repulsion betweenthe carboxylic groups of the ionic hydrogels results in apH-responsive swelling of the hydrogel such pH-responsiveswelling behavior can assist in the control of drug release[11 20ndash23]

In this study BCPAM hydrogels were synthesized usingBC dispersion and BC dissolved in NaOHurea solvent sys-tem Hydrogels were developed by using microwave irradia-tion instead of the conventional heating method to improvethe degree of grafting and reduce the time consumption Theresulting hydrogels were characterized using Fourier trans-form infrared spectroscopy (FT-IR) X-ray diffraction (XRD)and scanning electron microscopy (SEM) The swellingbehavior of the hydrogels was then determined at differentpH values and ionic strengths Finally drug loading andrelease behavior of the hydrogels were investigated to evaluatethe potential for the application of these hydrogels in drugdelivery

2 Experimental

21 Materials Acrylamide (AM) potassium persulfate(KPS) NN1015840-methylenebisacrylamide (MBA) and theophyl-linewere purchased fromSigmaAldrich JapanUrea sodiumhydroxide and other reagents were of analytical grade andused without further purification Phosphate buffer solutionsat pH 2 5 7 and 9 were prepared as described in the BritishPharmacopoeia Nata de coco was used as a source of BCand was procured from a local food company

22 Purification of Nata de Coco Nata de coco was purifiedas previously described [1] Briefly nata de coco was washedand soaked in distilled water to attain pH (5ndash7) To achievea constant weight the samples were then blended in a wetblender poured into trays and then freeze-dried Using apulverizer (Pulverisette 14 Frisch Germany) the BC sheetswere micronized to produce a fluffy BC powder

23 Synthesis of Hydrogels A solvent system consisting ofNaOHurea was used to dissolve the BC Two different ratiosof NaOH (6amp 8wv) and urea (4wv) were dissolved indistilled water to prepare the solvent system for dissolutionNext 25 g of BC powder was added to 100mL of solventwith constant stirring and stored at minus10∘C for 12 hThe frozensolid was then thawed and stirred extensively at 25∘C untila transparent solution was attained [24] To prepare the BCdispersion purified BC with a particle size in the range 50ndash100 120583mwas dispersed in distilledwater to produce 25 (wv)dispersion [25]

To synthesize the BCPAM hydrogels AM (20 g) wasadded to 20mL of freshly prepared BC solution followed bythe addition of potassium persulfate as an initiator (7wwof AM) and MBA (7ww of AM) as a crosslinker Nextthe reaction mixtures were irradiated using a microwaveirradiator (LG model MS2388K Korea) at 340W for 30 s tosynthesize hydrogels (SH) Similarly the hydrogels from thedispersed BC were produced using the same concentrationof AM crosslinker and initiator with the exception of BCdispersion being used instead of a solution (DH) SimilarlyPAM was prepared by exposure to microwave radiations inthe absence of BC as shown in Table 1

24 Characterization of the Hydrogels

241 Gel Fraction Determination The gel fractions (GF) ofthe hydrogels were determined to estimate the degree ofgrafting Freshly prepared hydrogel discs (12 cm in diameter)were dried in an oven at 60∘C to a constant weight (119882

0) The

dried hydrogel discs were then soaked in distilled water toremove any unreacted monomers or sol from the hydrogelsThe water was changed after 24 h and the absorbance of thesolvent used to soak the hydrogels was determined at 270 nmto detect the unreacted PAMThese extracted hydrogels werethen dried again to a constant weight (119882

1) at a temperature

of 60∘C in an ovenThe percentage of gel fraction (GF) wascalculated using (1) [13 14]

GF = 11988211198820

times 100 (1)

242 FT-IR Spectroscopic Analysis IR spectra of the sampleswere recorded using Perkin Elmer FT-IR Spectra 2000 atroom temperature (25∘C) The test specimens were preparedusing the KBr disc method and analyzed over the range of400ndash4000 cmminus1

243 X-Ray Diffraction X-ray diffractograms of the BC andhydrogels were obtained using an X-ray diffractometer (D8-Advance Bruker AXS) with Cu K120572 radiation at 40 kV and50mA in a differential angle range of 5ndash60∘ 2120579 [4]

244 Morphological Analysis Themorphology of the freeze-dried swollen hydrogels was examined using scanning-electron microscopy (Leo 1450 VP Germany) The freeze-dried samples were mounted on to an aluminum stub withdouble-sided carbon tape and coated with gold in a sputtercoater (SC500 BioRad UK) under argon atmosphere




NaOHurea ratio( wv)



119870 1198772

119870 1198772

119899

PAMDH

0102510

0000


09960996

01000111

08440841

00020002

09570954

07940775

SH64

2510 64 7329 plusmn 165 0991 0135 0824 0002 0932 0723SH84

2510 84 695 plusmn 305 0990 0149 0813 0002 0921 0712



SR =(Gs minus Gd)

Gdtimes 100 (2)



64 and SH

84) by using


DL =119882dg

119882gtimes 100 (3)








4






Microwave


NaOH Hydrolysis

+

+



MBA


BC

(Sodium acrylate)

Initiation


S2O8

O

O

OOO

O

O

OH

NH2

NH2NH2

ONa

ONa

(AM)

(AM)

2SO4

minus



64and SH

84) dispersed


64and SH




64 and SH



64and SH

84



BC

PAM

DH

3421 1658

1451

1667

2929 15681408

3398

2914

1163

1059

3215

3438

2924

1452

SH64

SH84

4000 3500 3000 2500 2000 1500 1000 500400(cmminus1)

T(

)


0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

Lin

(cou

nts)

Lin

(cou

nts)

6 10 20 30 40 50 60

2120579 scale

0123456789

1011121314151617181920212223242526times10

4

6 10 20 30 40 50 60 702120579 scale

BCPAMDH

SH64

SH84




64 and SH




64 and

SH84



(a) (b)

(c) (d)


84



and SH84


64and SH

84









0

500

1000

1500

2000

2500

3000

2 5 7 9

Swel

ling

ratio

()

pH

PAMDH

SH64

SH84

(a)

PAMDH

0

500

1000

1500

2000

2500

3000

05 M 01 M 001 M 0001 M

Swel

ling

ratio

()


SH64

SH84

(b)



Formulation


(mean plusmn SD)

Compressivestrain









64hydrogels






38 Swelling Studies


64and SH



64and SH

84clearly underlie








3

+) and




SH84


64and

SH84

revealed that SH64


84 The


0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500

Cum

ulat

ive r

elea

se (

)

Time (min)

PAMDH

SH64

SH84



4 Conclusions


Acknowledgments



References










































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






NaOHurea ratio( wv)



119870 1198772

119870 1198772

119899

PAMDH

0102510

0000


09960996

01000111

08440841

00020002

09570954

07940775

SH64

2510 64 7329 plusmn 165 0991 0135 0824 0002 0932 0723SH84

2510 84 695 plusmn 305 0990 0149 0813 0002 0921 0712



SR =(Gs minus Gd)

Gdtimes 100 (2)



64 and SH

84) by using


DL =119882dg

119882gtimes 100 (3)








4






Microwave


NaOH Hydrolysis

+

+



MBA


BC

(Sodium acrylate)

Initiation


S2O8

O

O

OOO

O

O

OH

NH2

NH2NH2

ONa

ONa

(AM)

(AM)

2SO4

minus



64and SH

84) dispersed


64and SH




64 and SH



64and SH

84



BC

PAM

DH

3421 1658

1451

1667

2929 15681408

3398

2914

1163

1059

3215

3438

2924

1452

SH64

SH84

4000 3500 3000 2500 2000 1500 1000 500400(cmminus1)

T(

)


0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

Lin

(cou

nts)

Lin

(cou

nts)

6 10 20 30 40 50 60

2120579 scale

0123456789

1011121314151617181920212223242526times10

4

6 10 20 30 40 50 60 702120579 scale

BCPAMDH

SH64

SH84




64 and SH




64 and

SH84



(a) (b)

(c) (d)


84



and SH84


64and SH

84









0

500

1000

1500

2000

2500

3000

2 5 7 9

Swel

ling

ratio

()

pH

PAMDH

SH64

SH84

(a)

PAMDH

0

500

1000

1500

2000

2500

3000

05 M 01 M 001 M 0001 M

Swel

ling

ratio

()


SH64

SH84

(b)



Formulation


(mean plusmn SD)

Compressivestrain









64hydrogels






38 Swelling Studies


64and SH



64and SH

84clearly underlie








3

+) and




SH84


64and

SH84

revealed that SH64


84 The


0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500

Cum

ulat

ive r

elea

se (

)

Time (min)

PAMDH

SH64

SH84



4 Conclusions


Acknowledgments



References










































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Microwave


NaOH Hydrolysis

+

+



MBA


BC

(Sodium acrylate)

Initiation


S2O8

O

O

OOO

O

O

OH

NH2

NH2NH2

ONa

ONa

(AM)

(AM)

2SO4

minus



64and SH

84) dispersed


64and SH




64 and SH



64and SH

84



BC

PAM

DH

3421 1658

1451

1667

2929 15681408

3398

2914

1163

1059

3215

3438

2924

1452

SH64

SH84

4000 3500 3000 2500 2000 1500 1000 500400(cmminus1)

T(

)


0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

Lin

(cou

nts)

Lin

(cou

nts)

6 10 20 30 40 50 60

2120579 scale

0123456789

1011121314151617181920212223242526times10

4

6 10 20 30 40 50 60 702120579 scale

BCPAMDH

SH64

SH84




64 and SH




64 and

SH84



(a) (b)

(c) (d)


84



and SH84


64and SH

84









0

500

1000

1500

2000

2500

3000

2 5 7 9

Swel

ling

ratio

()

pH

PAMDH

SH64

SH84

(a)

PAMDH

0

500

1000

1500

2000

2500

3000

05 M 01 M 001 M 0001 M

Swel

ling

ratio

()


SH64

SH84

(b)



Formulation


(mean plusmn SD)

Compressivestrain









64hydrogels






38 Swelling Studies


64and SH



64and SH

84clearly underlie








3

+) and




SH84


64and

SH84

revealed that SH64


84 The


0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500

Cum

ulat

ive r

elea

se (

)

Time (min)

PAMDH

SH64

SH84



4 Conclusions


Acknowledgments



References










































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




BC

PAM

DH

3421 1658

1451

1667

2929 15681408

3398

2914

1163

1059

3215

3438

2924

1452

SH64

SH84

4000 3500 3000 2500 2000 1500 1000 500400(cmminus1)

T(

)


0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

Lin

(cou

nts)

Lin

(cou

nts)

6 10 20 30 40 50 60

2120579 scale

0123456789

1011121314151617181920212223242526times10

4

6 10 20 30 40 50 60 702120579 scale

BCPAMDH

SH64

SH84




64 and SH




64 and

SH84



(a) (b)

(c) (d)


84



and SH84


64and SH

84









0

500

1000

1500

2000

2500

3000

2 5 7 9

Swel

ling

ratio

()

pH

PAMDH

SH64

SH84

(a)

PAMDH

0

500

1000

1500

2000

2500

3000

05 M 01 M 001 M 0001 M

Swel

ling

ratio

()


SH64

SH84

(b)



Formulation


(mean plusmn SD)

Compressivestrain









64hydrogels






38 Swelling Studies


64and SH



64and SH

84clearly underlie








3

+) and




SH84


64and

SH84

revealed that SH64


84 The


0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500

Cum

ulat

ive r

elea

se (

)

Time (min)

PAMDH

SH64

SH84



4 Conclusions


Acknowledgments



References










































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)

(c) (d)


84



and SH84


64and SH

84









0

500

1000

1500

2000

2500

3000

2 5 7 9

Swel

ling

ratio

()

pH

PAMDH

SH64

SH84

(a)

PAMDH

0

500

1000

1500

2000

2500

3000

05 M 01 M 001 M 0001 M

Swel

ling

ratio

()


SH64

SH84

(b)



Formulation


(mean plusmn SD)

Compressivestrain









64hydrogels






38 Swelling Studies


64and SH



64and SH

84clearly underlie








3

+) and




SH84


64and

SH84

revealed that SH64


84 The


0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500

Cum

ulat

ive r

elea

se (

)

Time (min)

PAMDH

SH64

SH84



4 Conclusions


Acknowledgments



References










































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

500

1000

1500

2000

2500

3000

2 5 7 9

Swel

ling

ratio

()

pH

PAMDH

SH64

SH84

(a)

PAMDH

0

500

1000

1500

2000

2500

3000

05 M 01 M 001 M 0001 M

Swel

ling

ratio

()


SH64

SH84

(b)



Formulation


(mean plusmn SD)

Compressivestrain









64hydrogels






38 Swelling Studies


64and SH



64and SH

84clearly underlie








3

+) and




SH84


64and

SH84

revealed that SH64


84 The


0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500

Cum

ulat

ive r

elea

se (

)

Time (min)

PAMDH

SH64

SH84



4 Conclusions


Acknowledgments



References










































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials









3

+) and




SH84


64and

SH84

revealed that SH64


84 The


0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500

Cum

ulat

ive r

elea

se (

)

Time (min)

PAMDH

SH64

SH84



4 Conclusions


Acknowledgments



References










































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




References










































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



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Rapid Synthesis of Superabsorbent Smart-Swelling Bacterial