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Nanoscience Days
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NSD2020
Online Posters
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Model pollutant degradation under visible radiation. The photocatalyst selection
A. M. Díez, Y. Kolen’ko
International Iberian Nanotechnology Laboratory, Braga, Portugal Email:[email protected]
Photocatalysis processes have been proposed lately as an alternative forwastewater remediation because of their easy set-up and the possibility of usingsolar radiation, which would make the process inexpensive [1]. However, the vastmajority of photocatalysts are powerful at short wavelengths (UVA, UVB) whichhave a limited presence on the solar spectrum.
This research was focused on the synthesis of visible radiation-activephotocatalysts. For that, TiO2 which is one of the best UVA photocatalyst [2], wasused as starting point and modified in order to extend its photo-response. For that,graphene oxide or other semiconductors (Fe3O4, SiO2) were added. Moreover, Cuwas affixed, favoring C-C breakage and also Fenton-like process if adding H2O2
(Eq. 1). Thus, generating radical species (HO●) which attack non-selectively theorganic matter [3].
Cu+ + H2O2 HO● + HO- + Cu2+ (Eq. 1)
Therefore, photocatalysis process can be coupled to photo-Fenton process for theefficient degradation of dye polluted effluents, enhancing the TiO2 performance(Table 1). Moreover, the process was optimized in terms of catalysts synthesisprocess and concentration, H2O2 concentration and pH. Being this combinedprocess suitable for the degradation of real polluted effluents.
Table 1. MB degradation after 1 hour of radiation under simulated visible radiation.
ProcessVis+TiO2
Vis+TiO2
+H2O2
TiO2
-GOTiO2-SiO2-Fe3O4-Cu
TiO2-SiO2-Fe3O4-Cu+ H2O2
MB degradation (%)
9.8 52.9 22.3 31.1 87.9
References
[1] N. A. Aziz, P. Palaniandy, H. A. Aziz, I. Dahlan. J. Chem. Res. 40, 704 (2016).[2] S. Shawaphun, T. Manangan, S. Wacharawichanant. Adv. Mat. Res. 93-94, 505 (2010).[3] H. Jin, X. Tian, Y. Nie, Z. Zhou, C. Yang, Y. Li, L. Lu. Environ. Sci. Technol.51, 12699(2017).
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Thermal conductance of a pillar-based phononic crystal at sub-Kelvin temperatures
T. Korkiamäki, I. M. W. Räisänen, T. A. Puurtinen and I. J. Maasilta. Nanoscience Center, Departments of Physics, University of Jyväskylä, Finland
Email: [email protected]
A phononic crystal (PnC) is an artificial periodic structure in one, two or three
dimensions that affects the propagation of phonons, the quanta of elastic waves. As
heat is mostly carried by phonons in insulators and semiconductors, PnC can be
utilised in controlling thermal transport in such materials. The mechanisms how
PnCs can work can be generally divided into two categories: one where incoherent,
diffusive particle-like scattering dominates, and another where coherent wave-like
scattering is operational [1]. Compared to hole-based PnCs [1,2], a much less
studied 2D crystals in thermal conductance manipulation are the pillar-based PnCs,
where the lattice is formed by a periodic array of pillars on a thin membrane (Fig.
1). For such PnCs, the phonon spectrum can also include localised resonances which
cannot carry heat.
In this work we have fabricated and measured the thermal conductance of a pillar-
based PnC, where aluminium pillars with a period of 5 µm, a height of 300 nm, and
with a 0.65 filling factor were deposited on a 300 nm thick silicon nitride film. The
measurements were conducted with a He3/He4 dilution refrigerator at sub-Kelvin
temperatures. The results showed a 65 % reduction in thermal conductance
compared to an unaltered film. Initially, it appears that the mechanism responsible
for the reduction was incoherent scattering. Possible causes for the breakdown of
the coherence include the pillar surface roughness, the pillar-film-interface, or grain
boundaries within the pillars.
Figure 1. A SEM image of a pillar-based phononic crystal structure with a heater-thermometer
in the middle.
[1] N. Zen et al. “Engineering thermal conductance using a two-dimensional
phononic crystal”. In: Nature Communications 5.3435 (2014).
[2] M. Maldovan. “Narrow Low-Frequency Spectrum and Heat Management by
Thermocrystals”. In: Phys. Rev. Lett. 110.025902 (2 Jan. 2013).
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Photoactivation of Bacterial Phytochromes Studied by Serial Femtosecond Crystallography
H. Takala, E. Claesson, W. Yang Wahlgren, G. Groenhof, E.A. Stojković,
J.A. Ihalainen, M. Schmidt, and S. Westenhoff
Department of Biological and Environmental Science, Nanoscience Center,
University of Jyväskylä, Finland
Email: [email protected]
Phytochromes are red light-sensing proteins found in plants, fungi and bacteria.
Upon photoactivation, phytochromes undergo a series of structural changes in order
alter their biochemical output activity. The structures of the resting and light-
activated states of bacteriophytochromes are partially known [1], but the details of
how the light cues are transferred into structural rearrangements are not well
understood. In particular, the primary structural response of the biliverdin
chromophore and the surrounding residues remains elusive.
Here, we present data from a phytochrome from Deinococcus radiodurans
collected by serial femtosecond crystallography (SFX) [2]. In particular, we show
structural snapshots of the protein at 1ps and 10ps after light excitation, which
provide a basis for understanding the primary photoresponses of phytochromes. The
snapshots reveal a liberation of the chromophore from the protein scaffold and
concomitant rotation of the biliverdin D-ring. We also find that the so-called pyrrole
water is displaced at 1ps, suggesting its hitherto unrecognized role in the
photochemistry of bacteriophytochromes.
Figure 1. The primary structural photoresponses captured in bacterial phytochromes help us
understand how plants see light.
References
[1] H. Takala, A. Björling, et al., Nature 509: 245-249 (2014).
[2] E. Claesson, W. Yuan Wahlgren, H. Takala, et al., Elife 9:e53514 (2020).
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Theoretical models for KPFM with flexible tip apexes
Ondrej Krejci
Aalto University, Finland Email: [email protected]
More than 10 years ago two types of Scanning Probe Microscopy (SPM) –Scanning Tunnelling Microscopy (STM) [1] and non-contact Atomic ForceMicroscopy (nc-AFM) [2] – showed a possibility to reveal positions of atoms onsmall flat organic molecules in real space without any damage to the sample.These two works noticeably enhanced the field of molecular, 1 and 2D materialstudies in surface science (i.e. [3]). The sub-molecular resolution was achieved byusage of non-reactive and flexible tip-apexes like CO-molecule [4,5].
Kelvin Probe Force Microscopy (KPFM) is a technique proceeded with combinednc-AFM/STM instrument, which basically measures the effect of applied voltagebetween the microscope tip and sample on the measured force. It has possibility tomeasure the changes of work-function on the microscale and electric field abovethe sample on the nanoscale. However, the physics behind KPFM signal withflexible-tip apexes showing the sub-molecular resolution, which could help withelemental recognition, remain unknown. Our work, employing small mechanisticmodels based on nc-AFM simulation techniques [4,5], suggests possible origins ofmeasured contrast (i.e. [6]). However, to fully understand all (possible) effects onthe measured signal a full DFT simulations with substrate, relaxing CO-tip withproper tip base [7] and applied electric field are necessary.
In this work, we will show the preliminary results of mechanistic models anddesign of the first DFT calculations simulating KPFM experiments and theycomparisons with experimental results. We believe that this work will help us tounderstand mechanisms and physics behind KPFM measurements performed withflexible tip-apexes and possibly can lead towards general recipe for chemicalresolution in SPM.
References
[1] R. Temirov et al., New J. Phys. 10, 2008, 053012.[2] L. Gross et al., Science 325, 2009, 1110.[3] A. Mistry et al., Chem. Eur. J. 21, 2015, 2011-2018. [4] P. Hapala et al., Phys. Rev. B 90, 2014, 085421.[5] P. Hapala et al., Phys. Rev. Lett. 113, 2015, 226101.[6] F. Mohn, et al., Nat. Nanotechnol. 7, 2012, 227-231.[7] F. Schulz et al., ACS Nano 12, 2018, 5274-5283.
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Triggering gelation via a selective deprotection reaction
R. Chevigny, a E. D. Sitsanidis, a A. Johansson, a E. Kalenius, c M. Pettersson, a M. Nissinen a
a Department of Chemistry, Nanoscience Centre, University of Jyväskylä, P.O. Box 35, FI-
40014,Finland. b Department of Chemistry, University of Jyväskylä, P.O. Box 35, FI-40014, Finland.
c Department of Chemistry, University of Jyväskylä, P.O. Box 35, FI-40014, Finland.
e-mail: [email protected]
We report the gelation trigger of N-(tert-butoxycarbonyl)-L-diphenylalanine-tert-butyl ester
(Boc-Phe-Phe-OtBu) 1, a di-protected diphenylalanine derivative by a selective deprotection
reaction. We followed the methodology reported by Lin et al. [1] for the deprotection of the
tert-butoxycarbonyl group (Boc-) in the presence of the tert-butyl ester group (-OtBu) under
acidic conditions. To the best of our knowledge, this is the first time that gelation is triggered
by a selective deprotection reaction other than enzymatic or photochemical reactions. The
gelation conditions were assessed and the mode of self-assembly of 1 investigated by FT-IR
and NMR spectroscopy. The chemical structure of the gelator building blocks (1-2) was
investigated by NMR and HR-MS spectroscopy. One of the major findings is the extension of
the life expectancy of the obtained organogel from 4 days (Figure 1b, left) to 6 months (Figure
1b, right) after performing swelling studies. Scanning electron microscopy also confirmed the
reshaping of the initial supramolecular network, from platted ribbons to fine elongated fibers.
The methodology presented here can be used for the in-situ preparation of soft materials by the
selective deprotection of precursor molecules towards potential gelator building blocks.
References
[1] L. S. Lin, J. Lanza T., S. E. De Laszlo, Q. Truong, T. Kamenecka and W. K. Hagmann, Tetrahedron
Lett., 41, 7013–7016, (2000).
Figure 1. a) Molecular formulae of the precursor 1 and the potential gelator 2. b) SEM imaging of
organogel before (left) and after (right) swelling
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Dynamical Coulomb Blockade in Sub-Micron Metal-Graphene Tunnel Junctions
J. I. Mastomäki, J. Manninen, V.-M. Hiltunen, A. Johansson, and I. J. Maasilta
Nanoscience Center, Departments of Physics, University of Jyväskylä, Finland
Email: [email protected]
Dynamical, or environmental, Coulomb blockade (DCB) in tunnel junction devices
is an important generalization of regular Coulomb blockade, which has found
applications for example in thermometry [1]. Characteristic to DCB is inelastic
tunneling, which provides detailed information about the electromagnetic
environment of the tunnel junction [2]. Detecting DCB usually requires carefully
engineered surroundings for tunnel junctions or complicated sample preparation [3],
and therefore, even if it is theoretically well-known, experimentally there is
relatively little research done.
Here, we present a simple way to produce tunable DCB junctions by contacting
graphene, a one-atom-thin layer of carbon, with sub-micron metal-metal oxide
contacts using conventional nanofabrication methods. In this system, the
environment is essentially the resistive graphene through which electrons must
travel between two tunnel junctions. DCB is clearly manifested in the measured
dynamical conductance, which shows a deep dip around the zero-bias at low
temperatures. The zero-bias dip has a strong temperature dependence in range
~100 mK to several K, and thus provides a way for local thermometry, which can
be applied in further studies of thermal transport in graphene nanodevices.
References
[1] F. Giazotto, et al., Rev. Mod. Phys., 78, 217 (2006).
[2] G.-L. Ingold and Y. V. Nazarov, Charge tunneling rates in ultrasmall junctions, in Single
Charge Tunneling: Coulomb Blockade Phenomena in Nanostructures, edited by H. Grabert and M. H. Devoret (Springer US, Boston, MA, 1992), p. 21.
[3] J. Senkpiel, et al., Phys. Rev. Lett. 124, 156803 (2020).
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The output domains of phytochromes amplify a downstreamfeedback loop between the PHY tongue and the chromophore
M. Kurttila1, J. Rumfeldt1, A. Winkler2 and J.A. Ihalainen1
1Nanoscience Center, Department of Biological and Environmental Science, University of Jyväskylä,Finland
2Institute of Biochemistry, Graz University of Technology, AustriaEmail: [email protected]
The structural dynamics of proteins are essential for their functionality. A photosensory proteincalled phytochrome includes a conserved ‘tongue’ extension (Fig. 1A). Gustavsson et al. haveshown by means of solution NMR that the tongue is structurally heterogeneous in the dark stateexchanging between β-sheet (adapted in the crystal structure) and random coil [1]. We usedFTIR spectroscopy together with pH-dependent UV-vis to demonstrate the effect of differentoutput domains to the dynamics of the tongue in a bacteriophytochrome from Deinococcusradiodurans (DrBphP). In the FTIR difference spectra the signal at 1631 cm-1 (in Pr),originating from the β-sheet secondary structure, is stronger in the full-length constructs thanin the truncated form without any output domain (Fig. 1B). The pH jump from pH 7.0 to 10.8detected by UV-vis follows the deprotonation of the biliverdin in the Pr state [2]. We argue thiscan only take place when the tongue switches from the “closed” β-sheet conformation to an“open” random coil, resulting in exposure of the (once buried) biliverdin to solvent. Thus, theslower rate of the deprotonation, observed as decrease of the absorption in 700 nm, in the full-length constructs reveals that the tongue is less dynamic than in the truncated DrBphP (Fig.1C). In the PaaC construct, which has a modulated output domain, the additional turn in thePHY and output domain connecting helix resulting from addition of 7 amino acids (PaaC +7)[3] seems to stabilize the tongue even more. Our experiments underline the tongue-stabilizingrole of the output modules and unveil a downstream feedback loop from the effector domainback to the photoconversion initializing chromophore.
Figure 1. A) The crystal structure of construct named PaaC, consisting of D. radiodurans chromophorebinding domain (CBD) and PHY-domain with Synechocystis adenylate cyclase output domain instead ofhistidine kinase, in Pr state [3] (PDB code: 6FHT). B) FTIR spectra measured in D2O with highlighted β-sheet signal, presumably from the tongue. C) The pH dependent UV-vis demonstrates the rate of thebiliverdin deprotonation.
References
[1] E. Gustavsson et al., Biophysical Journal 118, 2 (2020).[2] J. Rumfeldt et al., Photochemistry and Photobiology 95, 4 (2019).[3] S. Etzl, et al., J. Biol. Chem. 293, 23 (2018).
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Application of quantum dot nanoparticles for high-sensitive immunoassays
N.A. Taranova, A.V. Zherdev, and B.B. Dzantiev
A.N. Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian
Academy of Sciences, Russia Email:[email protected]
Lateral flow immunoassay (LFIA) is the effective solution for on-site testing. However, despite the rapidity of the LFIAs, their sensitivity often does not allow detecting trace amounts of analytes. The report presents new approaches that were proposed and realized to decrease the detection limits of LFIAs. Semiconductor nanoparticles named as quantum dots (QDs) demonstrated their potential for application in different areas, ranging from microelectronics to bioimaging. Advantages of QDs as labels for LFIA are based on their properties, which are achieved by variations in chemical composition, size (1-10 nm), and surface coverage. Conjugation of QDs with antibodies allow combining efficient immune binding and strong fluorescence [1].
We have characterized QDs as labels for LFIA and studied their advantages in comparison with such commonly used labels as colloidal gold. The application of QDs provides 10-20-fold increase of sensitivity for LFIA and simple visual control of the assay results. The integration of QDs with different emission spectra provides possibility for simple multiplex assay [2]. The test strip for LFIA in this case comprising several binding zones, where each specific immune reactants form complexes with QDs differing in fluorescence color. The multicolor ‘traffic light’ test system allows identifying analytes and measuring their concentrations based on the color of the bands in the test zone. This fluorescence-based LFIA was realized for simultaneous detection of three cardiomarkers. We have synthesized three conjugates, nanely red QDs – antibodies to troponin I, yellow QDs – antibodies to myoglobin and green QDs – antibodies to fatty acid binding protein. “Traffic light” LFIA was realized for simultaneous deteсtion of these three cardiomarkers. For example, the reached limit of detection of myoglobin is 0.4 ng/mL that accords to diagnostic demands.
This work was financially supported by the Russian Science Foundation (grant No. 20-73-00325).
References [1 ] H. Li B. Dong, L. Dou, W. Yu, X. Yu, K. Wen, Y. Ke, J. Shen, and Z. Wang. Sensors and Actuators B: Chemical, 324, 128771 (2020). [2] N.A. Taranova, A.N. Berlina, A.V. Zherdev, and B.B. Dzantiev. Biosensors and Bioelectronics, 63, 255-261 (2015).
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Surface characteristics control the attachment and functionality of(chimeric) avidin
Shao D.1, K. Tapio 1, S. Auer 2, J.J. Toppari1, V. Hytönen 2, Markus Ahlskog1
1 Nanoscience Center and Department of Physics, University of Jyväskylä, Finland ([email protected]) 2 BioMediTech, University of Tampere, Tampere, Finland
The physical adsorption (physisorption) of proteins to surfaces is an important butuncompletely understood factor in many biological processes, and of increasing significancein bionanotechnology as well [1]. Avidin is a most important protein due to the strong avidin-biotin binding which has numerous applications [2]. We have undertaken thoroughexperimentation on the physisorption of avidin, to chemically different flat surfaces, Si andgraphite, and also to the curved version of the latter, on multiwalled carbon nanotubes(MWNT) of different diameter.
Figure 1: Avidin molecules (in the middle) were deposited on topographically or chemically differentsurfaces. The flat topography was given by SiO2 or graphite while the MWNT surface was curved.MWNT and graphite is chemically similar while the SiO2 is distinct from these.
The difference between the behavior of avidin on Si and graphite is drastic, in that on Siavidin deposits as single globular tetrameric units, while on graphite it forms irregularnetworks of two layers thick filaments. On MWNTs avidin also deposits as one dimensionalformations, or stripes, but as opposed to the irregular network appearance on graphite, thecylindrical nanometer sized curvature orders the stripes in a perpendicular andquasiperiodical arrangement to the MWNT axis. We also demonstrated the preservedfunctionality of the deposited avidin with respect to biotin binding.
[1] Kastantin, M.; Langdon, B. B.; Schwartz, D. K. Advances in Colloid and InterfaceScience 207, 240 (2014). [2] Laitinen, O. H.; Nordlund, H. R.; Hytönen, V. P.; Kulomaa, M. S. Trends in Biotechnology 25, 269 – 277 (2007).
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Free-standing 2D metals from binary metal alloys
J. Nevalaita, and P. Koskinen
Nanoscience Center, Department of Physics, University of Jyväskylä, Finland Email: [email protected]
Recent experiment demonstrated the formation of free-standing Au monolayers byexposing Au-Ag alloy to electron beam irradiation [1]. Inspired by this discovery,we used semi-empirical effective medium theory simulations toinvestigate monolayer formation in 30 different binary metal alloys composed oflate d-series metals Ni, Cu, Pd, Ag, Pt, and Au [2]. In qualitative agreement withthe experiment, our molecular dynamics simulations find that the beam energyrequired to dealloy Ag atoms from Au-Ag alloy is smaller than the energy requiredto break the dealloyed Au monolayer. Our simulations suggest that similar methodcould also be used to form Au monolayers from Au-Cu alloy and Pt monolayersfrom Pt-Cu, Pt-Ni, and Pt-Pd alloys (Fig. 1).
Figure 1. Dealloying energy windows for five best alloy candidates and a schematic of theexperimental setup. Shown are electron beam energy ranges that correspond to no dealloying(blue), only alloying secondary metal while keeping primary metal monolayer intact (white),dealloying secondary metal and primary metal monolayer (red), and dealloying all atoms(black).
References
[1] X. Wang, C. Wang, C. Chen, H. Duan, and K. Du, Nano Lett. 19, 4560 (2019). [2] J. Nevalaita and P. Koskinen, AIP Adv. 10, 065327 (2020)
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Conformation-dependent phytochrome activates secondary signalling
Nanekar Rahul, Ihalainen Janne (2020)
Nanoscience Center, Department of Biological and Environmental Sciences, University of Jyväskylä, Finland
email: [email protected]
Red light sensing bacterial phytochromes relay the light signal via interaction with cognate
response regulator (RR) proteins. Phytochromes can switch between two conformationally
distinct states: resting (Pr) and illuminated (Pfr). Amount of either conformational state can be
populated using red (670nm) or far red (780nm) light. However Pfr conformation, over time, can
revert to Pr state through a process called dark reversion. Introduction of a single amino acid
mutation (F469W) slows down the dark reversion process (Figure A) enabling more detailed
bicohemical and biophysical characterization of the Pfr state phytochromes [1].
We have used UV-Vis spectrometry and Isothermal Titration Calorimetry to investigate the
phytochrome binding to its cognate RR. The Pr state phytochrome binds to RR with moderate
mid-micromolar (kD=3.7µM) affinity (Figure B) while Pfr state phytochrome does it strongly
(kD=0.6µM) (Figure C). Stronger binding affinity in Pfr state infers the favourable conformation
of the phytochrome for RR recruitment.
Figure: (A) Spectral properties show slowed down Pfr to Pr conversion of mutant (F469W) in comparison
with WT phytochrome. (B) and (C) show ITC determined binding constants for RR and F469W (mutant
phytochrome) in Pr and Pfr conformation, respectively.
References
[1] E. Sethe Burgie, Junrui Zhang, Richard D. Vierstra Structure 24, 448-457 (2016).
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Acoustic wave tunneling between adjacent anisotropicpiezoelectric solids: generalized theory
Zhuoran Geng, Ilari J. Maasilta
Nanoscience Center, Departments of Physics, University of Jyväskylä, Finland Email: [email protected]
Electroacoustic waves propagating in a semi-infinite piezoelectric half-space canhave a finite transmission into an adjacent piezoelectric solid, even through avacuum gap. In other words, sound can jump or tunnel across vacuum. Inparticular, with specific crystal orientations, the slow transverse (ST) waves canexcite so called pseudo-surface waves on both interfaces, leading to a unitytransmission. Although similar complete transmission of the electroacoustic wavehas been claimed in the past [1,2,3], there is still lack of proper study that isapplicable to an anisotropic medium with an arbitrary crystal cut.
In this presentation, by extending the Stroh formalism [4], we introduce ageneralized formalism for electroacoustic wave tunneling across a vacuum gap,calculate analytical and numerical illustrative examples, and present comparisonswith previous literature. In particular, the tunneling conditions for the unitytransmission of an acoustic wave through vacuum gap are presented and discussed.
Figure 1. (a) Schematic of two adjacent identical piezoelectric solids separated by a narrowvacuum gap. Laboratory coordinates are presented as xyz, while Z indicates the orientationof the crystal. (b) and (c) demonstrate the maximum amplitude transmission coefficients of aslow transvers (ST) wave with different crystal orientations and crystal cuts for ZnO.
References:
[1] M. Balakirev and A. Gorchakov, Sov. Phys. Solid State 19, 327 (1977) [2] A. N. Darinskii and M. Weihnacht, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 53, 412 (2006).[3] M. Prunnila and J. Meltaus, Phys. Rev. Lett. 105, 125501 (2010).[4] A. N. Stroh, J. Math. Phys. 41, 77 (1962).
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Observing targeted protein immobilization on (laser-oxidized) graphene in situ via Atomic Force Microscopy
J. Schirmer,a E.D. Sitsanidis,a K.K. Mentel,a V.J. Hiltunen,b P. Myllyperkiö,a M.
Nissinena and M. Petterssona
aNanoscience Center, Department of Chemistry, University of Jyväskylä, Finland bNanoscience Center, Department of Physics, University of Jyväskylä, Finland
Email: [email protected]
Our research focuses on the development of biocompatible interface between
graphene and nerve cells, towards implantable microchips for neuroapplications. To
promote neuronal growth, we intend to functionalize graphene-based surfaces with
proteins that support the proliferation of neurons. In previous studies, our group
developed a method to tuneably oxidize graphene monolayer via laser-induced two-
photon oxidization. [1] Here, we present the non-covalent immobilization of
Horseradish Peroxidase (HRP) on graphene-based surfaces. Atomic force
microscopy in a sealed liquid cell was applied to study the pH dependence of the
protein immobilization in situ.
Figure 1. Immobilization of HRP on (oxidized) graphene: AFM height sensor images (top) and
respective cross-section plots (bottom) in pH 5.1 (left), 7.1 (middle) and 9.1 (right).
References
[1] J. Aumanen, A. Johansson, J. Koivistoinen, P. Myllyperkiö, and M. Pettersson,
Patterning and Tuning of Electrical and Optical Properties of Graphene by Laser
Induced Two-Photon Oxidation, Nanoscale 7, 2851 (2015).
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Can we rely on zeta potential data for the soft nanoparticles in drug
delivery? A critical analysis.
Wali Inam1 Presenter, Sergey Filippov1 and Hongbo Zhang1
1Faculty of science and engineering, department of bioscience, Abo Akademi University, Turku,
Finland: Email: [email protected], [email protected], [email protected]
Zeta potential is an important parameter for nanoparticle characterization. It is measured at the
slipping plane, an imaginary boundary that segregates loosely associated ions in the diffusion
layer (around nanoparticle) from the ions moving in the bulk solution. Zeta potential is
estimated by measuring electrophoretic mobility of the particles under the influence of an
applied electric field. For hard particles (metal nanoparticles) henry’s equation (U/E =
2ƐζF(Ka)/3η) along with either smoluchowski (for higher ionic strength) or huckel (lower ionic
strength) approximation is used for appropriate prediction of zeta potential. Contrarily, for soft
particles (polymeric nanoparticles) Ohshima approximation is only possible approach to
estimate zeta potential.[1] Concept of zeta potential is not well explored for polymeric
nanoparticles used in drug delivery and biotechnological applications. [2][3] Zeta potential is
a delicate parameter, value of which depends on characteristic of particle and bulk solution.
Characterizing surface charge of nanoparticles via zeta potential may give misleading
conclusions, if factors effecting zeta potential are ignored. Thus, there is a dire need to run an
investigation to analyse how zeta potential of polymeric particles is affected by its ambience?
In this study six different polymeric nanoparticles (Acetelated dextran, AcDEX, Spermine
modified acetelated dextran, SpAcDEX, PLGA and HPMC-HF, MF and LF) were first
fabricated using microfluidics technology. Zeta potential of nanoparticles was studied as a
function of nanoparticle concentration, pH and ionic strength. Data analysis showed that zeta
potential alters inversely as concentration of nanoparticles and ionic strength solution is
increased (figure 1). Effect of pH on zeta potential is highly subjective to the nature of polymer
(figure 1). Further, this study suggest that electrophoretic mobility is a better predictor of
surface charge than zeta potential.
Figure 1 Zeta potential of AcDEX nanoparticles as a function of nanoparticle concentration
References
1. ROBERT J. HUNTER. ZETA POTENTIAL IN COLLOID SCIENCE Principles and
Applications. ACADEMIC PRESS INC, London, 1–60 (1988).
2. Wich PR, Fréchet JMJ. Degradable Dextran Particles for Gene Delivery Applications. Aust. J.
Chem. [Internet]. 65(1), 15 (2012).
3. Cui W, Li J, Decher G. Self-Assembled Smart Nanocarriers for Targeted Drug Delivery. Adv.
Mater. [Internet]. 28(6), 1302–1311 (2016).
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The effect of crystallization packing on the excited statedecay properties in Bacteriophytochromes – a microcrystal
study
Valentyna Kuznetsova1,2, Heli Lehtivuori1, Heikki Takala1, Janne A. Ihalainen1,#
1 Department of Biological and Environmental Sciences, Nanoscience Center, Universityof Jyvaskyla, Jyvaskyla, Finland
2 Institute of Physics, Faculty of Science University of South Bohemia, Ceske Budejovice,Czech Republic
Email: [email protected]
X-ray free electron lasers (XFEL) have opened a new era in structural biology [1].Today we are able to obtain crystal structures of (bio)molecules, while followingthe photoisomerization [2] or chemical reactions in ultrafast time scales. Yet thistype of experiments stays expensive and resource consuming. Apart from the needof high-power X-ray pulse formation and advanced detection facilities, theapproach requires microcrystals which diffract to considerably high resolution, to2.2 Å or lower, but at the same time show similar kinetic responses as detected insolution environment. Here, we demonstrate by means of transient absorption VIS/NIR laser spectroscopy how the crystal packing effects on the photochemicalresponse of truncated bacteriophytochrome modules (PAS-GAF and PAS-GAF-PHY). In contrast to solution, the first photoproduct, known as a Lumi-R, iscompletely abolished in the crystal state. Still, a contribution to an intermediatestate, can be discerned. We present the excitation power dependence data ofmicrocrystals excited state dynamics and discuss what may lead to differences inspectroscopic responses obtained in VIS/NIR laser laboratory and XFEL facilities.
References
[1] P.Mehrabi, et al., bioRxiv (2020). [2] E.Claesson, et al., eLife Sciences. 9 (2020).
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Redox-responsive tumor targeted dual-drug loadedbiocompatible metal-organic frameworks nanoparticles for
enhancing anticancer effects
C.Liu, X. Xu, J. Zhou, J. Yan, D. Wang and H. Zhang
Pharmaceutical Sciences Laboratory, Åbo Akademi University, Finland Email: [email protected]
Metal-organic frameworks (MOFs) have proven to be a promising class of drugcarriers due to their high porosity, crystalline properties with defined structureinformation, and abundant surface chemistry for further functionalization[1].However, there has not been extensive research on MOF-based drug carriers withstimuli-responsive, dual-drug delivery, and tumor targeting functions. Here, wedemonstrate the strategy of constructing a redox responsive and tumor-targetedMOF as dual-drug carrier by anchoring functional disulfide anhydride and folicacid molecules to the organic links of MOFs, respectively. The MOF compositesshow the controlled release of loaded 5-fluorouracil (5-FU) entrapped within UiO-66-NH2 nanostructures modified with dichloroacetic acid, which acts as asynergistical drug with 5-FU in cancer cells. In addition, the overexpressed GSHin cancer cells attacks the thiolate moiety and is oxidized in the process as itcleaves the disulfide bonds, thereby achieving redox stimuli-responsive drugsrelease in MOFs. The confocal laser scanning microscopy further proved thatconjugation of folic acid to the MOF surface can significantly enhance thetargeting uptake of cancer cells. This work paves the way to the construction ofstimuli responsive tumor-targeted Nano MOF based drug carriers with potentialfor cancer therapies.
Figure 1. The synthesis of 5-FU-DCA-UiO-DTDP-FA by post-modification of the surfaces ofthe UiO-66-NH2 with DTDPA and NH2-FA and the encapsulation of 5-FU into the pores ofthe frameworks for the targeted delivery of DCA and 5-FU
References
[1] D. Joseph, D. Liu, and W. Lin, Acc. Chem. Res. 44, 10 (2011): 957-968.
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A topological isomer of the Au25(SR)18- nanocluster
M.F. Matusa, S. Malolaa, E.K. Bonillab, B.M. Barngroverb,c, C.M. Aikensb and H.
Häkkinena
aNanoscience Center, Departments of Physics and Chemistry, University of Jyväskylä,
Finland. bDepartment of Chemistry, Kansas State University, Manhattan, USA. cDepartment of Chemistry, Stephen F. Austin State University, Nacogdoches, USA
Email: [email protected]
Structural isomerism in thiolate-protected gold nanoclusters Aun(SR)m has gained
great interest for investigation of structure−property relationships.[1,2] Density
Functional Theory (DFT) calculations have been instrumental in predicting the
existence of metal cluster isomers and their effects in measured ensemble
properties.[3-5] However, needed time scales for a comprehensive exploration of
phase space when mapping potential isomers precludes DFT and alternatives
methods need to be used instead. In this study, an interesting isomer of the know
Au25(SR)18- structure were discovered via Reactive Molecular Dynamics
simulations (Reax-MD) and confirmed by DFT. The isomer is topologically
connected to the known crystal structure by a low-barrier collective rotation of the
icosahedral Au13 core. The isomerization takes place without breaking of any Au-S
bonds. The predicted isomer is essentially iso-energetic with the known crystal
structure but has a distinctly different optical spectrum. It has a significantly larger
collision cross-section as compared to the known structure, which suggests it could
be detectable in gas phase ESI-MS-TOF experiments.
Figure 1. Schematic representation of the iso-energetic isomer of Au25(SR)18
- predicted by
Reactive-MD simulations.
References
[1] Y. Chen, et al., J. Am. Chem. Soc. 138, 1482 (2016).
[2] S. Malola and H. Hakkinen, J. Am. Chem. Soc. 141, 6006 (2019).
[3] F. Furche, et al., J. Chem. Phys. 117, 6982 (2002).
[4] H. Häkkinen, Chem. Soc. Rev. 37, 1847 (2008).
[5] H. Häkkinen, et al., J. Phys. Chem. A 107, 6168 (2003).
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Ion beam imaging and milling of the biological materials
M. Leppänen
Nanoscience Center, Departments of Physics, University of Jyväskylä, Finland
Email: [email protected]
Helium ion microscopy is a novel microscopy method that has several advantages
over conventional electron microscopy. Those are, for example, higher
magnification and the ability to cut materials. I will present some results about the
method with the antibacterial and other biological materials.
In a one study, it was found that ion microscopy is well suited to image bacteria and
viruses [1]. With the method, details of infectious viruses can be detected at different
stages of infection in a single sample. When the dose of the ion beam is increased,
it can be used to cut materials. This was exploited when antibacterial nanostructures
of the dragonfly wing were studied [2]. The bacteria on the wing were cleaved to
provide information about the interaction of the bacteria with nanostructures
(Figure 1). Imaging of the nanocellulose-based material has shown how important
the correct dose is to prevent any damage to the material [3]. Because the ion beam
can be used to cut, it can also damage the material when imaging.
Figure 1. Ion beam cut and imaged E.Coli bacteria on the dragonfly wing.
References
[1] M. Leppänen, et al., Advanced Biosystems, 1, 8, (2017).
[2] C. Bandara, et al., ACS Biomaterials Science & Engineering 6, 7, (2020).
[3] A. Ketola, et al., RSC Advances, 9, 27, (2019).
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Fabrication of stimuli-responsive nanogel for drug delivery application
Fadak Howaili1,3, Mahdi Abdollahi2, Majid Sadeghizadeh1 and Jessica M. Rosenholm3
1NanoBiotechnology Department, Faculty of Biological Science, Tarbiat Modares
University, Tehran, Iran 2Polymer Reaction Engineering Department, Faculty of Chemical Engineering, Tarbiat
Modares University, Tehran, Iran 3Pharmaceutical Sciences Laboratory, Faculty of Science and Engineering, Åbo Akademi
University, Turku, Finland Email: [email protected]
Nanogels are crosslinked polymer-based hydrogel nanoparticles, and due to their superior
properties including high drug loading capacity, low toxicity and stimuli responsiveness,
they are considered as next-generation drug delivery systems[1]. In this study, thermo-pH-
responsive nanogel (Ng) was synthesized by grafting poly (N-isopropyl acrylamide)
(PNIPAM) to chitosan (CS) in the presence of chemical crosslinker to serve as a drug carrier
agent[2]. We applied Fourier transform infrared spectroscopy (FTIR) to confirm successful
synthesis of Ng based on the CS and PNIPAM. The developed nanogel formulation was
thoroughly characterized by particle size distribution and zeta potential measurements in 4
different temperatures, Morphology and size measurements of nanogel were determined by
transmission electron microscopy (TEM). Nanogel was found to have a hydrodynamic size
of approximately 140 nm in diameter This work revealed that synthesized nanogel are
stimuli-responsive nanocarriers, which have a potential for delivery of hydrophobic
drugs[3].
Figure 1. FTIR spectrum of chitosan (CS), NIPAM and nanogel. Zeta potential and size measurement in different
temperature. SEM image of nanogel.
References
1. Maya, S., et al., Smart stimuli sensitive nanogels in cancer drug delivery and
imaging: a review. Current pharmaceutical design, 2013. 19(41): p. 7203-7218.
2. Leaf-nosed bat, in Encyclopædia Britannica. 2009, Encyclopædia Britannica
Online.
3. Ormategui, N., et al., Interaction of poly (Nisopropylacrylamide)(pNIPAM) based
nanoparticles and their linear polymer precursor with phospholipid membrane
models. Bioelectrochemistry, 2012. 87: p. 211-219.
a b c d
