82 results on '"Kargl R"'
Search Results
2. The European Polysaccharide Network of Excellence (EPNOE) research roadmap 2040 : Advanced strategies for exploiting the vast potential of polysaccharides as renewable bioresources
- Author
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Gericke, M., Amaral, A. J. R., Budtova, T., De Wever, P., Groth, T., Heinze, T., Höfte, H., Huber, A., Ikkala, O., Kapuśniak, J., Kargl, R., Mano, J. F., Másson, M., Matricardi, P., Medronho, B., Norgren, Magnus, Nypelö, T., Nyström, L., Roig, A., Sauer, M., Schols, H. A., van der Linden, J., Wrodnigg, T. M., Xu, C., Yakubov, G. E., Stana Kleinschek, K., Fardim, P., Gericke, M., Amaral, A. J. R., Budtova, T., De Wever, P., Groth, T., Heinze, T., Höfte, H., Huber, A., Ikkala, O., Kapuśniak, J., Kargl, R., Mano, J. F., Másson, M., Matricardi, P., Medronho, B., Norgren, Magnus, Nypelö, T., Nyström, L., Roig, A., Sauer, M., Schols, H. A., van der Linden, J., Wrodnigg, T. M., Xu, C., Yakubov, G. E., Stana Kleinschek, K., and Fardim, P.
- Abstract
Polysaccharides are among the most abundant bioresources on earth and consequently need to play a pivotal role when addressing existential scientific challenges like climate change and the shift from fossil-based to sustainable biobased materials. The Research Roadmap 2040 of the European Polysaccharide Network of Excellence (EPNOE) provides an expert's view on how future research and development strategies need to evolve to fully exploit the vast potential of polysaccharides as renewable bioresources. It is addressed to academic researchers, companies, as well as policymakers and covers five strategic areas that are of great importance in the context of polysaccharide related research: (I) Materials & Engineering, (II) Food & Nutrition, (III) Biomedical Applications, (IV) Chemistry, Biology & Physics, and (V) Skills & Education. Each section summarizes the state of research, identifies challenges that are currently faced, project achievements and developments that are expected in the upcoming 20 years, and finally provides outlines on how future research activities need to evolve.
- Published
- 2024
- Full Text
- View/download PDF
3. Differences in integrity of white matter and changes with training in spelling impaired children: a diffusion tensor imaging study
- Author
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Gebauer, D., Fink, A., Filippini, N., Johansen-Berg, H., Reishofer, G., Koschutnig, K., Kargl, R., Purgstaller, C., Fazekas, F., and Enzinger, C.
- Published
- 2012
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4. UV-Induced reduction of graphene oxide in cellulose nanofibril composites
- Author
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Pottathara, Y. B., primary, Thomas, S., additional, Kalarikkal, N., additional, Griesser, T., additional, Grohens, Y., additional, Bobnar, V., additional, Finšgar, M., additional, Kokol, V., additional, and Kargl, R., additional
- Published
- 2019
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5. Protein-repellent and antimicrobial nanoparticle coatings from hyaluronic acid and a lysine-derived biocompatible surfactant
- Author
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Bračič, M., primary, Fras-Zemljič, L., additional, Pérez, L., additional, Kogej, K., additional, Stana-Kleinschek, K., additional, Kargl, R., additional, and Mohan, T., additional
- Published
- 2017
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6. Selective immobilization and detection of DNA on biopolymer supports for the design of microarrays
- Author
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Kargl, R., primary, Vorraber, V., additional, Ribitsch, V., additional, Köstler, S., additional, Stana-Kleinschek, K., additional, and Mohan, T., additional
- Published
- 2015
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7. Differences in integrity of white matter and changes with training in spelling impaired children: a diffusion tensor imaging study
- Author
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Gebauer, D., primary, Fink, A., additional, Filippini, N., additional, Johansen-Berg, H., additional, Reishofer, G., additional, Koschutnig, K., additional, Kargl, R., additional, Purgstaller, C., additional, Fazekas, F., additional, and Enzinger, C., additional
- Published
- 2011
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8. Dyslexie und ihre neuronale Signatur
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Bartl-Pokorny, K., additional, Landerl, K., additional, Einspieler, C., additional, Enzinger, C., additional, Gebauer, D., additional, Fink, A., additional, Zhang, D., additional, Kozel, N., additional, Kargl, R., additional, Seither Preisler, A., additional, Vollmann, R., additional, and Marschik, P., additional
- Published
- 2011
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9. Polysaccharides: Structures and materials for biomedical applications
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Kargl, R., TAMILSELVAN MOHAN, and Kleinschek, K. S.
10. Hyaluronic acid conjugates of glycine peptides and L-tryptophan.
- Author
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Gürer F, Mohan T, Bračič M, Barlič A, Makuc D, Plavec J, Kleinschek KS, and Kargl R
- Subjects
- Humans, Magnetic Resonance Spectroscopy, Hyaluronic Acid chemistry, Tryptophan chemistry, Glycine chemistry, Peptides chemistry, Peptides pharmacology, Human Umbilical Vein Endothelial Cells drug effects
- Abstract
This work reports about the conjugation of glycine C-terminal ethyl and methyl ester peptides and L-tryptophan methyl ester with sodium hyaluronate in aqueous solutions using the peptide coupling agent DMTMM (or short DMT, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methyl-morpholinium chloride). Detailed infrared (IR) absorbance and
1 H and13 C (2D) NMR studies (heteronuclear multi-bond correlation spectroscopy, HMBC) confirmed covalent and regioselective amide bonds with the D-glucuronate, but also proves the presence of DMT traces in all conjugates. The ethyl ester`s methyl protons on the peptides` C-terminal could be used to quantify the degree of substitution of the peptide on the hyaluronate scaffold by NMR. The ester group also proved stable during conjugation and work-up, and could in some cases be selectively cleaved in water whilst leaving the amide bond intact as shown by potentiometric charge titration, NMR and IR. The conjugates did not influence the capability of human umbilical vein endothelial cells (HUVECs) to reduce MTS (5-[3-(carboxymethoxy)phenyl]-3-(4,5-dimethyl-2-thiazolyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt) to a formazan dye, which points towards a low cytotoxicity for the obtained products. The conjugation method and products could be tested for tissue engineering gels or drug delivery purposes with alternative, biologically active peptides., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)- Published
- 2024
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11. The European Polysaccharide Network of Excellence (EPNOE) research roadmap 2040: Advanced strategies for exploiting the vast potential of polysaccharides as renewable bioresources.
- Author
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Gericke M, Amaral AJR, Budtova T, De Wever P, Groth T, Heinze T, Höfte H, Huber A, Ikkala O, Kapuśniak J, Kargl R, Mano JF, Másson M, Matricardi P, Medronho B, Norgren M, Nypelö T, Nyström L, Roig A, Sauer M, Schols HA, van der Linden J, Wrodnigg TM, Xu C, Yakubov GE, Stana Kleinschek K, and Fardim P
- Subjects
- Polysaccharides
- Abstract
Polysaccharides are among the most abundant bioresources on earth and consequently need to play a pivotal role when addressing existential scientific challenges like climate change and the shift from fossil-based to sustainable biobased materials. The Research Roadmap 2040 of the European Polysaccharide Network of Excellence (EPNOE) provides an expert's view on how future research and development strategies need to evolve to fully exploit the vast potential of polysaccharides as renewable bioresources. It is addressed to academic researchers, companies, as well as policymakers and covers five strategic areas that are of great importance in the context of polysaccharide related research: (I) Materials & Engineering, (II) Food & Nutrition, (III) Biomedical Applications, (IV) Chemistry, Biology & Physics, and (V) Skills & Education. Each section summarizes the state of research, identifies challenges that are currently faced, project achievements and developments that are expected in the upcoming 20 years, and finally provides outlines on how future research activities need to evolve., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)
- Published
- 2024
- Full Text
- View/download PDF
12. 4-Axis 3D-Printed Tubular Biomaterials Imitating the Anisotropic Nanofiber Orientation of Porcine Aortae.
- Author
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Lackner F, Šurina P, Fink J, Kotzbeck P, Kolb D, Stana J, Grab M, Hagl C, Tsilimparis N, Mohan T, Stana Kleinschek K, and Kargl R
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- Animals, Humans, Swine, Tissue Engineering methods, Cell Culture Techniques methods, Printing, Three-Dimensional, Tissue Scaffolds chemistry, Biocompatible Materials chemistry, Nanofibers chemistry
- Abstract
Many of the peculiar properties of the vasculature are related to the arrangement of anisotropic proteinaceous fibers in vessel walls. Understanding and imitating these arrangements can potentially lead to new therapies for cardiovascular diseases. These can be pre-surgical planning, for which patient-specific ex vivo anatomical models for endograft testing are of interest. Alternatively, therapies can be based on tissue engineering, for which degradable in vitro cell growth substrates are used to culture replacement parts. In both cases, materials are desirable that imitate the biophysical properties of vessels, including their tubular shapes and compliance. This work contributes to these demands by offering methods for the manufacturing of anisotropic 3D-printed nanofibrous tubular structures that have similar biophysical properties as porcine aortae, that are biocompatible, and that allow for controlled nutrient diffusion. Tubes of various sizes with axial, radial, or alternating nanofiber orientation along the blood flow direction are manufactured by a customized method. Blood pressure-resistant, compliant, stable, and cell culture-compatible structures are obtained, that can be degraded in vitro on demand. It is suggested that these healthcare materials can contribute to the next generation of cardiovascular therapies of ex vivo pre-surgical planning or in vitro cell culture., (© 2023 The Authors. Advanced Healthcare Materials published by Wiley-VCH GmbH.)
- Published
- 2024
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13. 3D-Printed Collagen-Nanocellulose Hybrid Bioscaffolds with Tailored Properties for Tissue Engineering Applications.
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Dobaj Štiglic A, Lackner F, Nagaraj C, Beaumont M, Bračič M, Duarte I, Kononenko V, Drobne D, Madhan B, Finšgar M, Kargl R, Stana Kleinschek K, and Mohan T
- Subjects
- Humans, Biocompatible Materials pharmacology, Biocompatible Materials chemistry, Collagen chemistry, Cellulose pharmacology, Cellulose chemistry, Printing, Three-Dimensional, Tissue Engineering, Tissue Scaffolds chemistry
- Abstract
Hybrid collagen (Coll) bioscaffolds have emerged as a promising solution for tissue engineering (TE) and regenerative medicine. These innovative bioscaffolds combine the beneficial properties of Coll, an important structural protein of the extracellular matrix, with various other biomaterials to create platforms for long-term cell growth and tissue formation. The integration or cross-linking of Coll with other biomaterials increases mechanical strength and stability and introduces tailored biochemical and physical factors that mimic the natural tissue microenvironment. This work reports on the fabrication of chemically cross-linked hybrid bioscaffolds with enhanced properties from the combination of Coll, nanofibrillated cellulose (NFC), carboxymethylcellulose (CMC), and citric acid (CA). The bioscaffolds were prepared by 3D printing ink containing Coll-NFC-CMC-CA followed by freeze-drying, dehydrothermal treatment, and neutralization. Cross-linking through the formation of ester bonds between the polymers and CA in the bioscaffolds was achieved by exposing the bioscaffolds to elevated temperatures in the dry state. The morphology, pores/porosity, chemical composition, structure, thermal behavior, swelling, degradation, and mechanical properties of the bioscaffolds in the dry and wet states were investigated as a function of Coll concentration. The bioscaffolds showed no cytotoxicity to MG-63 human bone osteosarcoma cells as tested by different assays measuring different end points. Overall, the presented hybrid Coll bioscaffolds offer a unique combination of biocompatibility, stability, and structural support, making them valuable tools for TE.
- Published
- 2023
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14. Morphology and swelling of thin films of dialcohol xylan.
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Palasingh C, Kargl R, Stana Kleinschek K, Schaubeder J, Spirk S, Ström A, and Nypelö T
- Abstract
Polysaccharides are excellent network formers and are often processed into films from water solutions. Despite being hydrophilic polysaccharides, the typical xylans liberated from wood are sparsely soluble in water. We have previously suggested that an additional piece to the solubilization puzzle is modification of the xylan backbone via oxidative cleavage of the saccharide ring. Here, we demonstrate the influence of the degree of modification, i.e., degree of oxidation (DO) on xylan solubilization and consequent film formation and stability. Oxidized and reduced wood xylans (i.e., dialcohol xylans) with the highest DO (77 %) within the series exhibited the smallest hydrodynamic diameter (d
h ) of 60 nm in dimethylsulfoxide (DMSO). We transferred the modified xylans into films credit to their established solubility and then quantified the film water interactions. Dialcohol xylans with intermediate DOs (42 and 63 %) did not form continuous films. The films swelled slightly when subjected to humidity. However, the film with the highest DO demonstrated a significant moisture uptake that depended on the film mass and was not observed with the other modified grades or with unmodified xylan., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)- Published
- 2023
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15. Cytotoxicity and Antibacterial Efficacy of Betaine- and Choline-Substituted Polymers.
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Jurko L, Makuc D, Štern A, Plavec J, Žegura B, Bošković P, and Kargl R
- Abstract
Cationic charge has been widely used to increase polymer adsorption and flocculation of dispersions or to provide antimicrobial activity. In this work, cationization of hydroxyethyl cellulose (HEC) and polyvinyl alcohol (PVA) was achieved by covalently coupling betaine hydrochloride and choline chloride to the polymer backbones through carbonyl diimidazole (CDI) activation. Two approaches for activation were investigated. CDI in excess was used to activate the polymers' hydroxyls followed by carbonate formation with choline chloride, or CDI was used to activate betaine hydrochloride, followed by ester formation with the polymers' hydroxyls. The first approach led to a more significant cross-linking of PVA, but not of HEC, and the second approach successfully formed ester bonds. Cationic, nitrogen-bearing materials with varying degrees of substitution were obtained in moderate to high yields. These materials were analyzed by Fourier transform infrared spectroscopy, nuclear magnetic resonance, polyelectrolyte titration, and kaolin flocculation. Their dose-dependent effect on the growth of Staphylococcus aureus and Pseudomonas aeruginosa , and L929 mouse fibroblasts, was investigated. Significant differences were found between the choline- and betaine-containing polymers, and especially, the choline carbonate esters of HEC strongly inhibited the growth of S. aureus in vitro but were also cytotoxic to fibroblasts. Fibroblast cytotoxicity was also observed for betaine esters of PVA but not for those of HEC. The materials could potentially be used as antimicrobial agents for instance by coating surfaces, but more investigations into the interaction between cells and polysaccharides are necessary to clarify why and how bacterial and human cells are inhibited or killed by these derivatives, especially those containing choline., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)
- Published
- 2023
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16. 3D Printed Porous Nanocellulose-Based Scaffolds As Carriers for Immobilization of Glycosyltransferases.
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Lackner F, Liu H, Štiglic AD, Bračič M, Kargl R, Nidetzky B, Mohan T, and Kleinschek KS
- Subjects
- Porosity, Printing, Three-Dimensional, Cellulose chemistry, Tissue Scaffolds chemistry, Glycosyltransferases
- Abstract
Biocatalysis is increasingly becoming an alternative method for the synthesis of industrially relevant complex molecules. This can be realized by using enzyme immobilized polysaccharide-based 3D scaffolds as compatible carriers, with defined properties. Especially, immobilization of either single or multiple enzymes on a 3D printed polysaccharide scaffold, exhibiting well-organized interconnected porous structure and morphology, is a versatile approach to access the performance of industrially important enzymes. Here, we demonstrated the use of nanocellulose-based 3D porous scaffolds for the immobilization of glycosyltransferases, responsible for glycosylation in natural biosynthesis. The scaffolds were produced using an ink containing nanofibrillated cellulose (NFC), carboxymethyl cellulose (CMC), and citric acid. Direct-ink-writing 3D printing followed by freeze-drying and dehydrothermal treatment at elevated temperature resulted in chemically cross-linked scaffolds, featuring tunable negative charges (2.2-5.0 mmol/g), pore sizes (10-800 μm), fluid uptake capacity, and exceptional dimensional and mechanical stability in the wet state. The negatively charged scaffolds were applied to immobilize two sugar nucleotide-dependent glycosyltransferases (C-glycosyltransferase, Z
basic2 -CGT; sucrose synthase, Zbasic2 -SuSy), each harboring a cationic binding module (Zbasic2 ) to promote charge-based enzyme adsorption. Both enzymes were immobilized at ∼30 mg of protein/g of dry carrier (∼20% yield), independent of the scaffold used. Their specific activities were 0.50 U/mg (Zbasic2 -CGT) and 0.19 U/mg (Zbasic2 -SuSy), corresponding to an efficacy of 37 and 18%, respectively, compared to the soluble enzymes. The glycosyltransferases were coimmobilized and shown to be active in a cascade reaction to give the natural C-glycoside nothofagin from phloretin (1.0 mM; ∼95% conversion). All enzyme bound scaffolds showed reusability of a maximum of 5 consecutive reactions. These results suggest that the 3D printed and cross-linked NFC/CMC-based scaffolds could present a class of solid carriers for enzyme (co)-immobilization, with promising applications in glycosyltransferase-catalyzed synthesis and other fields of biocatalysis.- Published
- 2022
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17. Nano-fibrillated cellulose-based scaffolds for enzyme (co)-immobilization: Application to natural product glycosylation by Leloir glycosyltransferases.
- Author
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Liu H, Štiglic AD, Mohan T, Kargl R, Kleinschek KS, and Nidetzky B
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- Glycosylation, Cellulose metabolism, Uridine Diphosphate Glucose, Glycosyltransferases genetics, Glycosyltransferases metabolism, Biological Products
- Abstract
Polysaccharide-based scaffolds are promising carriers for enzyme immobilization. Here, we demonstrate a porous scaffold prepared by direct-ink-writing 3D printing of an ink consisting of nanofibrillated cellulose, carboxymethyl cellulose and citric acid for immobilization application. Negative surface charge introduced by the components made the scaffold amenable for an affinity-like immobilization via the cationic protein module Z
basic2 . Zbasic2 fusions of two sugar nucleotide-dependent glycosyltransferases (C-glycosyltransferase, Z-CGT; sucrose synthase, Z-SuSy) were immobilized individually, or co-immobilized, and applied to synthesize the natural C-glycoside nothofagin. The cascade reaction involved β-C-glycosylation of phloretin (10 mM, ~90 % conversion) from UDP-glucose, provided from sucrose and catalytic amounts of UDP (1.0 mM). Enzymes were co-immobilized at ~65 mg protein/g carrier to receive activities of 9.5 U/g (Z-CGT) and 4.5 U/g (Z-SuSy) in 22-33 % yield (protein) and an effectiveness of 23 % (Z-CGT) and 13 % (Z-SuSy). The scaffold-bound enzymes were recyclable for 5 consecutive reactions., Competing Interests: Declaration of competing interest The authors declare that there is no any conflict of interest., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)- Published
- 2022
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18. Unraveling the timescale of the structural photo-response within oriented metal-organic framework films.
- Author
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Klokic S, Naumenko D, Marmiroli B, Carraro F, Linares-Moreau M, Zilio SD, Birarda G, Kargl R, Falcaro P, and Amenitsch H
- Abstract
Fundamental knowledge on the intrinsic timescale of structural transformations in photo-switchable metal-organic framework films is crucial to tune their switching performance and to facilitate their applicability as stimuli-responsive materials. In this work, for the first time, an integrated approach to study and quantify the temporal evolution of structural transformations is demonstrated on an epitaxially oriented DMOF-1-on-MOF film system comprising azobenzene in the DMOF-1 pores (DMOF-1/AB). We employed time-resolved Grazing Incidence Wide-Angle X-Ray Scattering measurements to track the structural response of the DMOF-1/AB film upon altering the length of the azobenzene molecule by photo-isomerization ( trans -to- cis , 343 nm; cis -to- trans , 450 nm). Within seconds, the DMOF-1/AB response occurred fully reversible and over several switching cycles by cooperative photo-switching of the oriented DMOF-1/AB crystallites as confirmed further by infrared measurements. Our work thereby suggests a new avenue to elucidate the timescales and photo-switching characteristics in structurally responsive MOF film systems., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)
- Published
- 2022
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19. Organic acid cross-linked 3D printed cellulose nanocomposite bioscaffolds with controlled porosity, mechanical strength, and biocompatibility.
- Author
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Štiglic AD, Gürer F, Lackner F, Bračič D, Winter A, Gradišnik L, Makuc D, Kargl R, Duarte I, Plavec J, Maver U, Beaumont M, Kleinschek KS, and Mohan T
- Abstract
Herein, we fabricated chemically cross-linked polysaccharide-based three-dimensional (3D) porous scaffolds using an ink composed of nanofibrillated cellulose, carboxymethyl cellulose, and citric acid (CA), featuring strong shear thinning behavior and adequate printability. Scaffolds were produced by combining direct-ink-writing 3D printing, freeze-drying, and dehydrothermal heat-assisted cross-linking techniques. The last step induces a reaction of CA. Degree of cross-linking was controlled by varying the CA concentration (2.5-10.0 wt.%) to tune the structure, swelling, degradation, and surface properties (pores: 100-450 μm, porosity: 86%) of the scaffolds in the dry and hydrated states. Compressive strength, elastic modulus, and shape recovery of the cross-linked scaffolds increased significantly with increasing cross-linker concentration. Cross-linked scaffolds promoted clustered cell adhesion and showed no cytotoxic effects as determined by the viability assay and live/dead staining with human osteoblast cells. The proposed method can be extended to all polysaccharide-based materials to develop cell-friendly scaffolds suitable for tissue engineering applications., Competing Interests: The authors declare no competing interests., (© 2022 The Author(s).)
- Published
- 2022
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20. Polysaccharide peptide conjugates: Chemistry, properties and applications.
- Author
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Mohan T, Kleinschek KS, and Kargl R
- Subjects
- Biocompatible Materials, Diagnostic Imaging, Drug Delivery Systems, Tissue Engineering, Alginates chemistry, Chitosan chemistry, Dextrans chemistry, Glycoconjugates chemistry, Peptides chemistry
- Abstract
The intention of this publication is to give an overview on research related to conjugates of polysaccharides and peptides. Dextran, chitosan, and alginate were selected, to cover four of the most often encountered functional groups known to be present in polysaccharides. These groups are the hydroxyl, the amine, the carboxyl, and the acetal functionality. A collection of the commonly used chemical reactions for conjugation is provided. Conjugation results into distinct properties compared to the parent polysaccharide, and a number of these characteristics are highlighted. This review aims at demonstrating the applicability of said conjugates with a strong emphasis on biomedical applications, drug delivery, biosensing, and tissue engineering. Some suggestions are made for more rigorous chemistries and analytics that could be investigated. Finally, an outlook is given into which direction the field could be developed further. We hope that this survey provides the reader with a comprehensive summary and contributes to the progress of works that aim at synthetically combining two of the main building blocks of life into supramolecular structures with unprecedented biological response., (Copyright © 2021 The Author(s). Published by Elsevier Ltd.. All rights reserved.)
- Published
- 2022
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21. Solid Phase Peptide Synthesis on Chitosan Thin Films.
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Katan T, Kargl R, Mohan T, Steindorfer T, Mozetič M, Kovač J, and Stana Kleinschek K
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- Microscopy, Atomic Force, Quartz Crystal Microbalance Techniques, Solid-Phase Synthesis Techniques, Surface Properties, Water chemistry, Chitosan chemistry
- Abstract
Stable chitosan thin films can be promising substrates for creating nanometric peptide-bound polyglucosamine layers. Those are of scientific interest since they can have certain structural similarities to bacterial peptidoglycans. Such films were deposited by spin coating from chitosan solutions and modified by acetylation and N -protected amino acids. The masses of deposited materials and their stability in aqueous solutions at different pH values and water interaction were determined with a quartz crystal microbalance with dissipation (QCM-D). The evolution of the surface composition was followed by X-ray photoelectron (XPS) and attenuated total reflectance infrared (ATR-IR) spectroscopy. Morphological changes were measured by atomic force microscopy (AFM), while the surface wettability was monitored by by static water contact angle measurements. The combination of the characterization techniques enabled an insight into the surface chemistry for each treatment step and confirmed the acetylation and coupling of N -protected glycine peptides. The developed procedures are seen as first steps toward preparing thin layers of acetylated chitin, potentially imitating the nanometric peptide substituted glycan layers found in bacterial cell walls.
- Published
- 2022
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22. One-Step Fabrication of Hollow Spherical Cellulose Beads: Application in pH-Responsive Therapeutic Delivery.
- Author
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Mohan T, Ajdnik U, Nagaraj C, Lackner F, Dobaj Štiglic A, Palani T, Amornkitbamrung L, Gradišnik L, Maver U, Kargl R, and Stana Kleinschek K
- Subjects
- Anti-Inflammatory Agents, Non-Steroidal chemistry, Diclofenac chemistry, Drug Carriers chemistry, Drug Delivery Systems, Humans, Hydrogen-Ion Concentration, Materials Testing, Molecular Structure, Particle Size, Porosity, Surface Properties, Anti-Inflammatory Agents, Non-Steroidal pharmacology, Biocompatible Materials chemistry, Cellulose chemistry, Diclofenac pharmacology, Inflammation drug therapy, Pain drug therapy
- Abstract
The path to greater sustainability and the development of polymeric drug delivery systems requires innovative approaches. The adaptation and use of biobased materials for applications such as targeted therapeutic delivery is, therefore, in high demand. A crucial part of this relates to the development of porous and hollow structures that are biocompatible, pH-responsive, deliver active substances, and contribute to pain relief, wound healing, tissue regeneration, and so forth. In this study, we developed a facile single-step and water-based method for the fabrication of hollow spherical cellulose beads for targeted drug release in response to external pH stimuli. Through base-catalyzed deprotection, hydrophobic solid and spherical cellulose acetate beads are transformed into hydrophilic cellulose structures with a hollow interior (wall thickness: 150 μm and inner diameter: 650 μm) by a stepwise increment of temperature and treatment time. Besides the pH-responsive fluid uptake properties, the hollow cellulose structures exhibit a maximum encapsulation efficiency of 20-85% diclofenac (DCF), a nonsteroidal anti-inflammatory drug, used commonly to treat pain and inflammatory diseases. The maximum amount of DCF released in vitro increased from 20 to 100% when the pH of the release medium increased from pH 1.2 to 7.4. As for the DCF release patterns and kinetic models at specific pH values, the release showed a diffusion- and swelling-controlled profile, effortlessly fine-tuned by external environmental pH stimuli. Overall, we show that the modified beads exhibit excellent characteristics for transport across the gastrointestinal tract and enhance the bioavailability of the drug. Their therapeutic efficacy and biocompatibility are also evident from the studies on human fibroblast cells. We anticipate that this platform could support and inspire the development of novel sustainable and effective polysaccharide-based delivery systems.
- Published
- 2022
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23. Rapid Functionalization of Polytetrafluorethylene (PTFE) Surfaces with Nitrogen Functional Groups.
- Author
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Vesel A, Zaplotnik R, Primc G, Mozetič M, Katan T, Kargl R, Mohan T, and Kleinschek KS
- Abstract
The biocompatibility of body implants made from polytetrafluoroethylene (PTFE) is inadequate; therefore, the surface should be grafted with biocompatible molecules. Because PTFE is an inert polymer, the adhesion of the biocompatible film may not be appropriate. Therefore, the PFTE surface should be modified to enable better adhesion, preferably by functionalization with amino groups. A two-step process for functionalization of PTFE surface is described. The first step employs inductively coupled hydrogen plasma in the H-mode and the second ammonia plasma. The evolution of functional groups upon treatment with ammonia plasma in different modes is presented. The surface is saturated with nitrogen groups within a second if ammonia plasma is sustained in the H-mode at the pressure of 35 Pa and forward power of 200 W. The nitrogen-rich surface film persists for several seconds, while prolonged treatment causes etching. The etching is suppressed but not eliminated using pulsed ammonia plasma at 35 Pa and 200 W. Ammonia plasma in the E-mode at the same pressure, but forward power of 25 W, causes more gradual functionalization and etching was not observed even at prolonged treatments up to 100 s. Detailed investigation of the XPS spectra enabled revealing the surface kinetics for all three cases.
- Published
- 2021
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24. Non-Equilibrium Plasma Methods for Tailoring Surface Properties of Polyvinylidene Fluoride: Review and Challenges.
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Vesel A, Zaplotnik R, Primc G, Mozetič M, Katan T, Kargl R, Mohan T, and Kleinschek KS
- Abstract
Modification and functionalization of polymer surface properties is desired in numerous applications, and a standard technique is a treatment with non-equilibrium gaseous plasma. Fluorinated polymers exhibit specific properties and are regarded as difficult to functionalize with polar functional groups. Plasma methods for functionalization of polyvinylidene fluoride (PVDF) are reviewed and different mechanisms involved in the surface modification are presented and explained by the interaction of various reactive species and far ultraviolet radiation. Most authors used argon plasma but reported various results. The discrepancy between the reported results is explained by peculiarities of the experimental systems and illustrated by three mechanisms. More versatile reaction mechanisms were reported by authors who used oxygen plasma for surface modification of PVDF, while plasma sustained in other gases was rarely used. The results reported by various authors are analyzed, and correlations are drawn where feasible. The processing parameters reported by different authors were the gas pressure and purity, the discharge configuration and power, while the surface finish was predominantly determined by X-ray photoelectron spectroscopy (XPS) and static water contact angle (WCA). A reasonably good correlation was found between the surface wettability as probed by WCA and the oxygen concentration as probed by XPS, but there is hardly any correlation between the discharge parameters and the wettability.
- Published
- 2021
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25. Water-based carbodiimide mediated synthesis of polysaccharide-amino acid conjugates: Deprotection, charge and structural analysis.
- Author
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Gürer F, Kargl R, Bračič M, Makuc D, Thonhofer M, Plavec J, Mohan T, and Kleinschek KS
- Subjects
- Carboxymethylcellulose Sodium chemical synthesis, Glycine chemical synthesis, Molecular Structure, Tryptophan chemical synthesis, Carbodiimides chemistry, Carboxymethylcellulose Sodium analogs & derivatives, Glycine analogs & derivatives, Indicators and Reagents chemistry, Tryptophan analogs & derivatives
- Abstract
We report here a one-step aqueous method for the synthesis of isolated and purified polysaccharide-amino acid conjugates. Two different types of amino acid esters: glycine methyl ester and L-tryptophan methyl ester, as model compounds for peptides, were conjugated to the polysaccharide carboxymethylcellulose (CMC) in water using carbodiimide at ambient conditions. Detailed and systematic pH-dependent charge titration and spectroscopy (infrared, nuclear magnetic resonance:
1 H,13 C- DEPT 135,1 H-13 C HMBC/HSQC correlation), UV-vis, elemental and ninhydrin analysis provided solid and direct evidence for the successful conjugation of the amino acid esters to the CMC backbone via an amide bond. As the concentration of amino acid esters increased, a conjugation efficiency of 20-80% was achieved. Activated charcoal aided base-catalyzed deprotection of the methyl esters improved the solubility of the conjugates in water. The approach proposed in this work should have the potential to tailor the backbone of polysaccharides containing di- or tri-peptides., (Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.)- Published
- 2021
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26. Succinylation of Polyallylamine: Influence on Biological Efficacy and the Formation of Electrospun Fibers.
- Author
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Jurko L, Bračič M, Hribernik S, Makuc D, Plavec J, Jerenec F, Žabkar S, Gubeljak N, Štern A, and Kargl R
- Abstract
Succinylation of proteins is a commonly encountered reaction in biology and introduces negatively charged carboxylates on previously basic primary amine groups of amino acid residues. In analogy, this work investigates the succinylation of primary amines of the synthetic polyelectrolyte polyallylamine (PAA). It investigates the influence of the degree of succinylation on the cytotoxicity and antibacterial activity of the resulting polymers. Succinylation was performed in water with varying amounts of succinic anhydride and at different pH values. The PAA derivatives were analyzed in detail with respect to molecular structure using nuclear magnetic resonance and infrared absorbance spectroscopy. Polyelectrolyte and potentiometric charge titrations were used to elucidate charge ratios between primary amines and carboxylates in the polymers. The obtained materials were then evaluated with respect to their minimum inhibitory concentration against Staphylococcus aureus and Pseudomonas aeruginosa . The biocompatibility was assessed using mouse L929 fibroblasts. The degree of succinylation decreased cytotoxicity but more significantly reduced antibacterial efficacy, demonstrating the sensitivity of the fibroblast cells against this type of ampholytic polyelectrolytes. The obtained polymers were finally electrospun into microfiber webs in combination with neutral water-soluble polyvinyl alcohol. The resulting non-woven could have the potential to be used as wound dressing materials or coatings.
- Published
- 2021
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27. Influence of Charge and Heat on the Mechanical Properties of Scaffolds from Ionic Complexation of Chitosan and Carboxymethyl Cellulose.
- Author
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Dobaj Štiglic A, Kargl R, Beaumont M, Strauss C, Makuc D, Egger D, Plavec J, Rojas OJ, Stana Kleinschek K, and Mohan T
- Subjects
- Carboxymethylcellulose Sodium, Hot Temperature, Humans, Materials Testing, Tissue Scaffolds, Chitosan
- Abstract
As one of the most abundant, multifunctional biological polymers, polysaccharides are considered promising materials to prepare tissue engineering scaffolds. When properly designed, wetted porous scaffolds can have biomechanics similar to living tissue and provide suitable fluid transport, both of which are key features for in vitro and in vivo tissue growth. They can further mimic the components and function of glycosaminoglycans found in the extracellular matrix of tissues. In this study, we investigate scaffolds formed by charge complexation between anionic carboxymethyl cellulose and cationic protonated chitosan under well-controlled conditions. Freeze-drying and dehydrothermal heat treatment were then used to obtain porous materials with exceptional, unprecendent mechanical properties and dimensional long-term stability in cell growth media. We investigated how complexation conditions, charge ratio, and heat treatment significantly influence the resulting fluid uptake and biomechanics. Surprisingly, materials with high compressive strength, high elastic modulus, and significant shape recovery are obtained under certain conditions. We address this mostly to a balanced charge ratio and the formation of covalent amide bonds between the polymers without the use of additional cross-linkers. The scaffolds promoted clustered cell adhesion and showed no cytotoxic effects as assessed by cell viability assay and live/dead staining with human adipose tissue-derived mesenchymal stem cells. We suggest that similar scaffolds or biomaterials comprising other polysaccharides have a large potential for cartilage tissue engineering and that elucidating the reason for the observed peculiar biomechanics can stimulate further research.
- Published
- 2021
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28. Anticoagulant Activity of Cellulose Nanocrystals from Isora Plant Fibers Assembled on Cellulose and SiO 2 Substrates via a Layer-by-Layer Approach.
- Author
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Mohan T, Chirayil CJ, Nagaraj C, Bračič M, Steindorfer TA, Krupa I, Maadeed MAAA, Kargl R, Thomas S, and Stana Kleinschek K
- Abstract
In this study, we report the isolation of cellulose nanocrystals (CNCs) from Isora plant fibers by sulfuric acid hydrolysis and their assembly on hydrophilic cellulose and silicon-di-oxide (SiO
2 ) surfaces via a layer-by-layer (LBL) deposition method. The isolated CNCs were monodispersed and exhibited a length of 200-300 nm and a diameter of 10-20 nm, a negative zetapotential (-34-39 mV) over a wide pH range, and high stability in water at various concentrations. The multi-layered structure, adsorbed mass, conformational changes, and anticoagulant activity of sequentially deposited anionic (sulfated) CNCs and cationic polyethyleneimine (PEI) on the surfaces of cellulose and SiO2 by LBL deposition were investigated using a quartz crystal microbalance technique. The organization and surface features (i.e., morphology, thickness, wettability) of CNCs adsorbed on the surfaces of PEI deposited at different ionic strengths (50-300 mM) of sodium chloride were analysed in detail by profilometry layer-thickness, atomic force microscopy and contact angle measurements. Compared to cellulose (control sample), the total coagulation time and plasma deposition were increased and decreased, respectively, for multilayers of PEI/CNCs. This study should provide new possibilities to fabricate and tailor the physicochemical properties of multilayer films from polysaccharide-based nanocrystals for various biomedical applications.- Published
- 2021
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29. Protein repellent anti-coagulative mixed-charged cellulose derivative coatings.
- Author
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Bračič M, Mohan T, Kargl R, Grießer T, Heinze T, and Stana Kleinschek K
- Subjects
- Amination, Anticoagulants pharmacology, Biocompatible Materials pharmacology, Cellulose pharmacology, Humans, Hydrogen-Ion Concentration, Kinetics, Membranes, Artificial, Polyelectrolytes chemistry, Protein Binding drug effects, Protons, Serum Albumin, Bovine chemistry, Static Electricity, Sulfuric Acid Esters chemistry, Thrombin antagonists & inhibitors, Thrombin metabolism, Water chemistry, Anticoagulants chemistry, Biocompatible Materials chemistry, Blood Coagulation drug effects, Cellulose analogs & derivatives, Polyesters chemistry
- Abstract
This study describes the formation of cellulose based polyelectrolyte charge complexes on the surface of biodegradable polycaprolactone (PCL) thin films. Anionic sulphated cellulose (CS) and protonated cationic amino cellulose (AC) were used to form these complexes with a layer-by-layer coating technique. Both polyelectrolytes were analyzed by charge titration methods to elucidate their pH-value dependent protonation behavior. A quartz crystal microbalance with dissipation (QCM-D) in combination with X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to follow the growth, stability and water content of up to three AC/CS bi-layers in aqueous environment. This was combined with coagulation studies on one, two and three bilayers of AC/CS, measuring the thrombin formation rate and the total coagulation time of citrated blood plasma with QCM-D. Stable mixed charged bilayers could be prepared on PCL and significantly higher masses of AC than of CS were present in these complexes. Strong hydration due to the presence of ammonium and sulphate substituents on the backbone of cellulose led to a significant BSA repellent character of three bilayers of AC/CS coatings. The total plasma coagulation time was increased in comparison to neat PCL, indicating an anticoagulative nature of the coatings. Surprisingly, a coating solely composed of an AC layer significantly prolonged the total coagulation time on the surfaces although it did not prevent fibrinogen deposition. It is suggested that these cellulose derivative-based coatings can therefore be used to prevent unwanted BSA deposition and fibrin clot formation on PCL to foster its biomedical application., (Copyright © 2020 Elsevier Ltd. All rights reserved.)
- Published
- 2021
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30. Comparison of Trimethylsilyl Cellulose-Stabilized Carbonate and Hydroxide Nanoparticles for Deacidification and Strengthening of Cellulose-Based Cultural Heritage.
- Author
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Amornkitbamrung L, Bračič D, Bračič M, Hribernik S, Malešič J, Hirn U, Vesel A, Kleinschek KS, Kargl R, and Mohan T
- Abstract
Herein, colloidal dispersions of alkaline nanoparticles (NPs: CaCO
3 and Mg(OH)2 ) are stabilized by trimethylsilyl cellulose (TMSC) in hexamethyldisiloxane and employed to treat historical wood pulp paper by an effortless dip-coating technique. Both alkaline NPs exhibit high stability and no size and shape changes upon stabilization with the polymer, as shown by UV-vis spectroscopy and transmission electron microscopy. The long-term effect of NP/TMSC coatings is investigated in detail using accelerated aging. The results from the pH-test and back-titration of coated papers show a complete acid neutralization (pH ∼ 7.4) and introduction of adequate alkaline reserve even after prolonged accelerated aging. Scanning electron microscopy-energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and infrared and water contact angle measurements showed the introduction of a thin and smooth hydrophobic NP/TMSC coating on the paper fibers. Acid-catalyzed desilylation of TMSC was observed by declining C-Si infrared absorbance peaks upon aging. The CaCO3 coatings are superior to Mg(OH)2 with respect to a reduced yellowing and lower cellulose degradation upon aging as shown by colorimetric measurements and degree of polymerization analysis. The tensile strength and folding endurance of coated and aged papers are improved to 200-300 and 50-70% as illustrated by tensile strength and double folding endurance measurements., Competing Interests: The authors declare no competing financial interest., (© 2020 American Chemical Society.)- Published
- 2020
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31. How can we understand the influence of nanoparticles on the coagulation of blood?
- Author
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Kargl R and Kleinschek KS
- Subjects
- Adsorption, Blood Coagulation, Surface Properties, Nanoparticles
- Published
- 2020
- Full Text
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32. Generic Method for Designing Self-Standing and Dual Porous 3D Bioscaffolds from Cellulosic Nanomaterials for Tissue Engineering Applications.
- Author
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Mohan T, Dobaj Štiglic A, Beaumont M, Konnerth J, Gürer F, Makuc D, Maver U, Gradišnik L, Plavec J, Kargl R, and Stana Kleinschek K
- Abstract
Three-dimensional scaffolds (3D) with controlled shape, dual porosity and long-term mechanical and dimensional stability in biofluids are of interest as biotemplates in tissue engineering. Herein, self-standing and lightweight cellulose-based biogenic scaffolds with a spatially structured morphology, macropores and interconnected micropores were fabricated using a combination of direct ink writing 3D printing and freeze-drying techniques. This was achieved by developing a water-based and low-cost bicomponent ink based on commercially available nanofibrillated cellulose (NFC) and carboxymethyl cellulose (CMC). Physical cross-linking through dehydrothermal treatment significantly increased the surface hardness, indentation modulus, compression strength, as well as the dimensional stability of the scaffolds in biofluids, in comparison to untreated materials. However, no differences in the spectra of solid state nuclear magnetic resonance or infrared were observed for dehydrothermal treated samples, suggesting that the increase of mechanical properties and dimensional stability is based on the physical cross-linking of functional groups both at the interface between NFC and CMC. The supramolecular structure of the polymers was well-preserved as disclosed by X-ray diffraction measurements. The cross-linked scaffolds showed high proliferation, viability, and attachment of human bone tissue derived osteoblast cells (hFOB). The simple and straightforward avenue proposed here for the design of cellulose-based fibrous inks and dual porous scaffolds from the commercially available materials and without the need of any additional cross-linkers should pave the way for the development of implantable, degradable scaffolds and cell-laden biomaterials for bone tissue regeneration and 3D bioprinting applications.
- Published
- 2020
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33. Chemical Structure-Antioxidant Activity Relationship of Water-Based Enzymatic Polymerized Rutin and Its Wound Healing Potential.
- Author
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Pivec T, Kargl R, Maver U, Bračič M, Elschner T, Žagar E, Gradišnik L, and Kleinschek KS
- Abstract
The flavonoid rutin (RU) is a known antioxidant substance of plant origin. Its potential application in pharmaceutical and cosmetic fields is, however, limited, due to its low water solubility. This limitation can be overcome by polymerization of the phenolic RU into polyrutin (PR). In this work, an enzymatic polymerization of RU was performed in water, without the addition of organic solvents. Further, the chemical structure of PR was investigated using
1 H NMR, and FTIR spectroscopy. Size-exclusion chromatography (SEC) was used to determine the molecular weight of PR, while its acid/base character was studied by potentiometric charge titrations. Additionally, this work investigated the antioxidant and free radical scavenging potential of PR with respect to its chemical structure, based on its ability to (i) scavenge non biological stable free radicals (ABTS), (ii) scavenge biologically important oxidants, such as O2 •, NO•, and OH•, and (iii) chelate Fe2+ . The influence of PR on fibroblast and HaCaT cell viability was evaluated to confirm the applicability of water soluble PR for wound healing application., Competing Interests: The authors declare no conflict of interest.- Published
- 2019
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34. Affinity of Serum Albumin and Fibrinogen to Cellulose, Its Hydrophobic Derivatives and Blends.
- Author
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Kargl R, Bračič M, Resnik M, Mozetič M, Bauer W, Stana Kleinschek K, and Mohan T
- Abstract
This work describes the preparation of spin-coated thin polymer films composed of cellulose (CE), ethyl cellulose (EC), and cellulose acetate (CA) in the form of bi- or mono-component coatings on sensors of a quartz crystal microbalance with dissipation monitoring (QCM-D). Depending on the composition and derivative, hydrophilicity can be varied resulting in materials with different surface properties. The surfaces of mono- and bi-component films were also analyzed by atomic force microscopy (AFM) and large differences in the morphologies were found comprising nano- to micrometer sized pores. Extended protein adsorption studies were performed by a QCM-D with 0.1 and 10 mg mL
-1 bovine serum albumin (BSA) and 0.1 and 1 mg mL-1 fibrinogen from bovine plasma in phosphate buffered saline. Analysis of the mass of bound proteins was conducted by applying the Voigt model and a comparison was made with the Sauerbrey wet mass of the proteins for all films. The amount of deposited proteins could be influenced by the composition of the films. It is proposed that the observed effects can be exploited in biomaterial science and that they can be used to extent the applicability of bio-based polymer thin films composed of commercial cellulose derivatives.- Published
- 2019
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35. Functional dextran amino acid ester particles derived from N-protected S-trityl-L-cysteine.
- Author
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Bratuša A, Elschner T, Heinze T, Fröhlich E, Hribernik S, Božič M, Žagar E, Kleinschek KS, Thonhofer M, and Kargl R
- Subjects
- Cysteine chemistry, Dextrans chemistry, Particle Size, Surface Properties, Amino Acids chemistry, Cysteine analogs & derivatives, Esters chemistry
- Abstract
This work describes the derivatization of dextran using N-(tert-butyloxycarbonyl)-S-(trityl)-L-cysteine in the presence of N,N'-carbonyldiimidazole (CDI) as a coupling agent. Homogeneous reactions in dimethyl sulfoxide allowed for an efficient coupling of the amino acid derivative to the polymer backbone. Derivatization was confirmed by infrared and
13 C NMR spectroscopy, size exclusion chromatography and elemental analysis. The presence of hydrophobic protecting groups resulted in a product that can be shaped into water-insoluble particles stable in an aqueous environment and non-toxic for lung epithelial cells. It is suggested that materials composed of ester bonds between amino acids and polysaccharides are useful for targeted drug delivery, bio-imaging or surface functionalization., (Copyright © 2019. Published by Elsevier B.V.)- Published
- 2019
- Full Text
- View/download PDF
36. Nano- and Micropatterned Polycaprolactone Cellulose Composite Surfaces with Tunable Protein Adsorption, Fibrin Clot Formation, and Endothelial Cellular Response.
- Author
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Mohan T, Nagaraj C, Nagy BM, Bračič M, Maver U, Olschewski A, Stana Kleinschek K, and Kargl R
- Subjects
- Cell Line, Cell Survival drug effects, Humans, Blood Coagulation drug effects, Cellulose chemistry, Cellulose pharmacology, Endothelial Cells metabolism, Fibrin metabolism, Polyesters chemistry, Polyesters pharmacology
- Abstract
This work describes the interaction of the human blood plasma proteins albumin, fibrinogen, and γ-globulins with micro- and nanopatterned polymer interfaces. Protein adsorption studies were correlated with the fibrin clotting time of human blood plasma and with the growth of primary human pulmonary artery endothelial cells (hECs) on these patterns. It was observed that blends of polycaprolactone (PCL) and trimethylsilyl-protected cellulose form various thin-film patterns during spin coating, depending on the mass ratio of the polymers in the spinning solutions. Vapor-phase acid-catalyzed deprotection preserves these patterns but yields interfaces that are composed of hydrophilic cellulose domains enclosed by hydrophobic PCL. The blood plasma proteins are repelled by the cellulose domains, allowing for a suggested selective protein deposition on the PCL domains. An inverse proportional correlation is observed between the amount of cellulose present in the films and the mass of irreversibly adsorbed proteins. This results in significantly increased fibrin clotting times and lower masses of deposited clots on cellulose-containing films as revealed by quartz crystal microbalance with dissipation measurements. Cell viability of hECs grown on these surfaces was directly correlated with higher protein adsorption and faster clot formation. The results show that presented patterned polymer composite surfaces allow for a controllable blood plasma protein coagulation and a significant biological response from hECs. It is proposed that this knowledge can be utilized in regenerative medicine, cell cultures, and artificial vascular grafts by a careful choice of polymers and patterns.
- Published
- 2019
- Full Text
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37. Estimation of the magnitude of quadrupole relaxation enhancement in the context of magnetic resonance imaging contrast.
- Author
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Kruk D, Masiewicz E, Umut E, Petrovic A, Kargl R, and Scharfetter H
- Subjects
- Bismuth chemistry, Hydrogen chemistry, Nanoparticles chemistry, Proton Magnetic Resonance Spectroscopy, Contrast Media chemistry, Magnetic Resonance Imaging methods
- Abstract
Magnetic Resonance Imaging (MRI) is one of the most powerful diagnostic tools providing maps of
1 H relaxation times of human bodies. The method needs, however, a contrast mechanism to enlarge the difference in the relaxation times between healthy and pathological tissues. In this work, we discuss the potential of a novel contrast mechanism for MRI based on Quadrupole Relaxation Enhancement (QRE) and estimate the achievable value of QRE under the most favorable conditions. It has turned out that the theoretically possible enhancement factors are smaller than those of typical paramagnetic contrast agents, but in turn, the field-selectivity of QRE-based agents makes them extremely sensitive to subtle changes of the electric field gradient in the tissue. So far, QRE has been observed for solids (in most cases for14 N) as a result of very slow dynamics and anisotropic spin interactions, believed to be necessary for QRE to appear. We show the first evidence that QRE can be achieved in solutions of compounds containing a high spin nucleus (209 Bi) as the quadrupole element. The finding of QRE in a liquid state is explained in terms of spin relaxation theory based on the stochastic Liouville equation. The results confirm the relaxation theory and motivate further exploration of the potential of QRE for MRI.- Published
- 2019
- Full Text
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38. Chitin nanowhisker - Inspired electrospun PVDF membrane for enhanced oil-water separation.
- Author
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Gopi S, Kargl R, Kleinschek KS, Pius A, and Thomas S
- Subjects
- Electrons, Oils chemistry, Porosity, Tensile Strength, Water chemistry, Chitin chemistry, Polyvinyls chemistry
- Abstract
The requirement of promoting a revolution in filtration technology has led to growing devotion in advanced functional materials such as electrospun membranes for filtering devices as a solution for providing water at lower energy costs. In this study, electrospun polyvinylidene fluoride membranes were fabricated by reinforcing 0.5 and 1 wt. % of chitin nanowhiskers in order to improve their thermal stability, mechanical properties, pure water flux and oil-water filtration performance for the possible application as filtration membranes. Morphological analysis revealed the porous and fibrous structure of membranes which confirmed by BET surface area analysis. Incorporation of chitin nanowhiskers improved the mechanical properties of the membranes such as elongation at break and tensile strength (specifically at 1 wt. % of chitin nanowhisker) while resulted in substantial enhancement of their thermal properties. Furthermore, polyvinylidene fluoride/chitin nanowhisker membranes showed enhanced oil-water separation ability, while reinforcement of chitin nanowhisker led to increase pure water flux rate, which measured as a crucial point in filtration membranes. The oil-water separation results compared with a commercial polyvinylidene fluoride membrane and the results signified the potential of electrospun polyvinylidene fluoride/chitin nanowhisker to be used for filtration application., (Copyright © 2018 Elsevier Ltd. All rights reserved.)
- Published
- 2018
- Full Text
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39. Nanofibrous polysaccharide hydroxyapatite composites with biocompatibility against human osteoblasts.
- Author
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Gašparič P, Kurečič M, Kargl R, Maver U, Gradišnik L, Hribernik S, Kleinschek KS, and Smole MS
- Subjects
- Cells, Cultured, Humans, Polysaccharides chemistry, Biocompatible Materials chemistry, Durapatite chemistry, Nanofibers, Osteoblasts cytology, Tissue Engineering, Tissue Scaffolds
- Abstract
Regenerative medicine has a high demand for defined scaffold materials that promote cell growth, stabilize the tissue during maturation and provide a proper three dimensional structure that allows the exchange of nutrients. In many instances nanofiber composites have already shown their potential for such applications. This work elaborates the development of polysaccharide based nanofibers with integrated hydroxyapatite nanoparticles. A detailed study on the formation of electrospun nanofibres from aqueous mixtures of carboxymethyl cellulose polyethylene oxide was performed. The influence of different processing conditions and spinning solution properties using a nozzle-less electrospinning device was systematically studied. Optimized parameters were used to incorporate hydroxyapatite nanoparticles into the fibers. Nanofibers were additionally hydrophobized with alkenyl succinic anhydride (ASA) to render them insoluble in water. The nanofiber webs were thoroughly investigated with respect to morphology, chemical composition and inorganic content. Time dependent biocompatibility testing of the materials with human bone-derived osteoblasts showed no significant reduction in cell viability for the developed materials composed of carboxymethyl cellulose/polyethyleneoxide. Cells grown on hydrophobized materials show similar viability as those grown on a commercial collagen/apatite matrix., (Copyright © 2017 Elsevier Ltd. All rights reserved.)
- Published
- 2017
- Full Text
- View/download PDF
40. Multilayered Polysaccharide Nanofilms for Controlled Delivery of Pentoxifylline and Possible Treatment of Chronic Venous Ulceration.
- Author
-
Stana J, Stergar J, Gradišnik L, Flis V, Kargl R, Fröhlich E, Stana Kleinschek K, Mohan T, and Maver U
- Subjects
- Cell Line, Humans, Alginates chemistry, Chitosan chemistry, Nanostructures chemistry, Pentoxifylline administration & dosage, Platelet Aggregation Inhibitors administration & dosage, Varicose Ulcer drug therapy
- Abstract
Local drug delivery systems made from nontoxic polysaccharide nanofilms have an enormous potential in wound care. A detailed understanding of the structural, surface, physicochemical, and cytotoxic properties of such systems is crucial to design clinically efficacious materials. Herein, we fabricated polysaccharide-based nanofilms onto either a 2D model (SiO
2 and Au sensors) or on nonwoven alginate 3D substrates using an alternating assembly of N,N,N-trimethylchitosan (TMC) and alginic acid (ALG) by a spin-assisted layer-by-layer (LbL) technique. These TMC/ALG multilayered nanofilms are used for a uniform encapsulation and controlled release of pentoxifylline (PTX), a potent anti-inflammatory drug for treatment of the chronic venous ulceration. We show a tailorable film growth and mass, morphology, as well as surface properties (charge, hydrophilicity, porosity) of the assembled nanofilms through control of the coating during the spin-assisted assembly. The uniform distribution of the encapsulated PTX in the TMC/ALG nanofilms is preserved even with when the amount of the incorporated PTX increases. The PTX release mechanism from the model and real systems is studied in detail and is very comparable for both systems. Finally, different cell-based assays illustrated the potential of the TMC/ALG multilayer system in wound care (e.g., treatment chronic venous ulceration) applications, including a decrease of TNF-α secretion, a common indicator of inflammation.- Published
- 2017
- Full Text
- View/download PDF
41. Nonspecific protein adsorption on cationically modified Lyocell fibers monitored by zeta potential measurements.
- Author
-
Payerl C, Bračič M, Zankel A, Fischer WJ, Kaschowitz M, Fröhlich E, Kargl R, Stelzer F, and Spirk S
- Subjects
- Adsorption, Hydrogen-Ion Concentration, Serum Albumin, Bovine chemistry, Static Electricity, Surface Properties, Chitosan chemistry, Proteins chemistry
- Abstract
Nonspecific protein deposition on Lyocell fibers via a cationization step was explored by adsorption of two different N,N,N-trimethyl chitosan chlorides (TMCs). Both, the cationization and the subsequent protein deposition steps were performed and monitored in situ by evaluating the zeta potential using the streaming potential method. Both employed TMCs (degree of substitution with N
+ Me3 Cl groups: 0.27 and 0.64) irreversibly adsorb on the fibers as proven by charge reversal (-12 to +7mV for both derivatives) after the final rinsing step. Onto these cationized fibers, BSA was deposited at different pH values (4, 5, and 7). Charge titrations revealed that close to the isoelectric point of BSA (4.7), BSA deposition was particularly favored, while at lower pH values (pH 4), hardly any adsorption took place due to electrostatic repulsion of the cationic fibers and the positively charged BSA. This work sets the foundation for further investigations to use zeta potential measurements for protein adsorption studies on fibrous materials., (Copyright © 2017 Elsevier Ltd. All rights reserved.)- Published
- 2017
- Full Text
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42. Synthesis and film formation of furfuryl- and maleimido carbonic acid derivatives of dextran.
- Author
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Elschner T, Obst F, Stana-Kleinschek K, Kargl R, and Heinze T
- Subjects
- Carbamates chemical synthesis, Dextrans chemical synthesis, Furans chemical synthesis, Maleimides chemical synthesis, Molecular Structure, Wettability, Carbamates chemistry, Dextrans chemistry, Furans chemistry, Maleimides chemistry
- Abstract
Carbonic acid derivatives of dextran possessing furfuryl- and maleimido moieties were synthesized and processed into thin films by spin coating. First, products with different degrees of substitution (DS) of up to 3.0 and substitution patterns were obtained and characterized by NMR- and FTIR spectroscopy, as well as elemental analysis. Thin films possessing maleimide groups were obtained by spin coating of maleimido dextran (furan-protected) and dextran furfuryl carbamate that was converted with bismaleimide. The removal of the protecting group (furan) on the thin film was monitored by QCM-D and compared with gravimetric analysis of the bulk material. Film morphology and wettability were determined by means of AFM and contact angle measurements., (Copyright © 2016 Elsevier Ltd. All rights reserved.)
- Published
- 2017
- Full Text
- View/download PDF
43. Interaction of Tissue Engineering Substrates with Serum Proteins and Its Influence on Human Primary Endothelial Cells.
- Author
-
Mohan T, Niegelhell K, Nagaraj C, Reishofer D, Spirk S, Olschewski A, Stana Kleinschek K, and Kargl R
- Subjects
- Cells, Cultured, Endothelial Cells cytology, Fibrinogen metabolism, Humans, Hydrophobic and Hydrophilic Interactions, Immunoglobulins metabolism, Materials Testing, Quartz Crystal Microbalance Techniques, Serum Albumin metabolism, Surface Properties, Tissue Engineering, Blood Proteins metabolism, Cell Adhesion physiology, Endothelial Cells metabolism, Polyesters metabolism, Polymers chemistry
- Abstract
Polymer-based biomaterials particularly polycaprolactone (PCL) are one of the most promising substrates for tissue engineering. The surface chemistry of these materials plays a major role since it governs protein adsorption, cell adhesion, viability, degradation, and biocompatibility in the first place. This study correlates the interaction of the most abundant serum proteins (albumin, immunoglobulins, fibrinogen) with the surface properties of PCL and its influence on the morphology and metabolic activity of primary human arterial endothelial cells that are seeded on the materials. Prior to that, thin films of PCL are manufactured by spin-coating and characterized in detail. A quartz crystal microbalance with dissipation (QCM-D), a multiparameter surface plasmon resonance spectroscopy instrument (MP-SPR), wettability data, and atomic force microscopy are combined to elucidate the pH-dependent protein adsorption on the PCL substrates. Primary endothelial cells are cultured on the protein modified polymer, and conclusions are drawn on the significant impact of type and form of proteins coatings on cell morphology and metabolic activity.
- Published
- 2017
- Full Text
- View/download PDF
44. Exploring Nonspecific Protein Adsorption on Lignocellulosic Amphiphilic Bicomponent Films.
- Author
-
Strasser S, Niegelhell K, Kaschowitz M, Markus S, Kargl R, Stana-Kleinschek K, Slugovc C, Mohan T, and Spirk S
- Subjects
- Adsorption, Surface-Active Agents chemistry, Triticum chemistry, Lignin chemistry, Membranes, Artificial, Serum Albumin, Bovine chemistry
- Abstract
In this contribution, we explore the interaction of lignocellulosics and proteins aiming at a better understanding of their synergistic role in natural systems. In particular, the manufacturing and characterization of amphiphilic bicomponent thin films composed of hydrophilic cellulose and a hydrophobic lignin ester in different ratios is presented which may act as a very simplified model for real systems. Besides detailed characterizations of the films and mechanisms to explain their formation, nonspecific protein adsorption using bovine serum albumin (BSA) onto the films was studied using a quartz crystal microbalance with dissipation (QCM-D). As it turns out, the rather low nonspecific protein adsorption of BSA on cellulose is further reduced when these hydrophobic lignins are incorporated into the films. The lignin ester acts in these blend films as sacrificial component, probably via an emulsification mechanism. Additionally, the amphiphilicity of the films may prevent the adsorption of BSA as well. Although there are some indications, it remains unclear whether any kind of protein interactions in such systems are of specific nature.
- Published
- 2016
- Full Text
- View/download PDF
45. Designing Hydrophobically Modified Polysaccharide Derivatives for Highly Efficient Enzyme Immobilization.
- Author
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Mohan T, Rathner R, Reishofer D, Koller M, Elschner T, Spirk S, Heinze T, Stana-Kleinschek K, and Kargl R
- Subjects
- Benzylamines chemistry, Biopolymers chemistry, Hydrophobic and Hydrophilic Interactions, Polysaccharides chemistry, Polystyrenes chemistry, Surface Properties, Water chemistry, Biocatalysis, Biosensing Techniques, Enzymes, Immobilized chemistry, Horseradish Peroxidase chemistry
- Abstract
In this contribution, a hydrophobically modified polysaccharide derivative is synthesized in an eco-friendly solvent water by conjugation of benzylamine with the backbone of the biopolymer. Owing to the presence of aromatic moieties, the resulting water-soluble polysaccharide derivative self-assembles spontaneously and selectively from solution on the surface of nanometric thin films and sheets of polystyrene (PS). The synthetic polymer modified in this way bears a biocompatible nanolayer suitable for the immobilization of horseradish peroxidase (HRP), a heme-containing metalloenzyme often employed in biocatalysis and biosensors. Besides the detailed characterization of the polysaccharide derivative, a quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy (AFM) are used to investigate the binding efficiency and interaction of HRP with the tailored polysaccharide interfaces. Subsequent enzyme activity tests reveal details of the interaction of HRP with the solid support. The novel polysaccharide derivative and its use as a material for the selective modification of PS lead to a beneficial, hydrophilic environment for HRP, resulting in high enzymatic activities and a stable immobilization of the enzyme for biocatalytic and analytic purposes.
- Published
- 2015
- Full Text
- View/download PDF
46. Antifouling coating of cellulose acetate thin films with polysaccharide multilayers.
- Author
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Mohan T, Kargl R, Tradt KE, Kulterer MR, Braćić M, Hribernik S, Stana-Kleinschek K, and Ribitsch V
- Subjects
- Adsorption, Cellulose chemistry, Microscopy, Atomic Force, Serum Albumin, Bovine chemistry, Surface Properties, Wettability, Carboxymethylcellulose Sodium chemistry, Cellulose analogs & derivatives, Chitosan chemistry
- Abstract
In this investigation, partially deacetylated cellulose acetate (DCA) thin films were prepared and modified with hydrophilic polysaccharides with the layer-by-layer (LbL) technique. As polysaccharides, chitosan (CHI) and carboxymethyl cellulose (CMC) were used. DCA thin films were manufactured by exposing spin coated cellulose acetate to potassium hydroxide solutions for various times. The deacetylation process was monitored by attenuated total reflectance-infrared spectroscopy, film thickness and static water contact angle measurements. A maximum of three bilayers was created from the alternating deposition of CHI and CMC on the DCA films under two different conditions namely constant ionic strengths and varying pH values of the CMC solutions. Precoatings of CMC at pH 2 were used as a base layer. The sequential deposition of CMC and CHI was investigated with a quartz crystal microbalance with dissipation, film thickness, static water contact angle and atomic force microscopy (AFM) measurements. The versatility and applicability of the developed functional coatings was shown by removing the multilayers by rinsing with mixtures containing HCl/NaCl. The developed LbL coatings are used for studying the fouling behavior of bovine serum albumin (BSA)., (Copyright © 2014 Elsevier Ltd. All rights reserved.)
- Published
- 2015
- Full Text
- View/download PDF
47. Photolithographic patterning of cellulose: a versatile dual-tone photoresist for advanced applications.
- Author
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Wolfberger A, Petritz A, Fian A, Herka J, Schmidt V, Stadlober B, Kargl R, Spirk S, and Griesser T
- Abstract
In many areas of science and technology, patterned films and surfaces play a key role in engineering and development of advanced materials. Here, we present a versatile toolbox that provides an easy patterning method for cellulose thin films by means of photolithography and enzymatic digestion. A patterned UV-illumination of trimethylsilyl cellulose thin films containing small amounts of a photo acid generator leads to a desilylation reaction and thus to the formation of cellulose in the irradiated areas. Depending on the conditions of development, either negative and positive type cellulose structures can be obtained, offering lateral resolutions down to the single-digit micro meter range by means of contact photolithography. In order to highlight the potential of this material for advanced patterning techniques, cellulose structures with sub-µm resolution are fabricated by means of two-photon absorption lithography. Moreover, these photochemically structured cellulose thin films are successfully implemented as dielectric layers in prototype organic thin film transistors. Such photopatternable dielectric layers are crucial for the realization of electrical interconnects for demanding organic device architectures.
- Published
- 2015
- Full Text
- View/download PDF
48. Triggering protein adsorption on tailored cationic cellulose surfaces.
- Author
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Mohan T, Niegelhell K, Zarth CS, Kargl R, Köstler S, Ribitsch V, Heinze T, Spirk S, and Stana-Kleinschek K
- Subjects
- Adsorption physiology, Animals, Cations, Cattle, Protein Binding physiology, Surface Properties, Cellulose chemistry, Cellulose metabolism, Serum Albumin, Bovine chemistry, Serum Albumin, Bovine metabolism
- Abstract
The equipment of cellulose ultrathin films with BSA (bovine serum albumin) via cationization of the surface by tailor-made cationic celluloses is described. In this way, matrices for controlled protein deposition are created, whereas the extent of protein affinity to these surfaces is controlled by the charge density and solubility of the tailored cationic cellulose derivative. In order to understand the impact of the cationic cellulose derivatives on the protein affinity, their interaction capacity with fluorescently labeled BSA is investigated at different concentrations and pH values. The amount of deposited material is quantified using QCM-D (quartz crystal microbalance with dissipation monitoring, wet mass) and MP-SPR (multi-parameter surface plasmon resonance, dry mass), and the mass of coupled water is evaluated by combination of QCM-D and SPR data. It turns out that adsorption can be tuned over a wide range (0.6-3.9 mg dry mass m(-2)) depending on the used conditions for adsorption and the type of employed cationic cellulose. After evaluation of protein adsorption, patterned cellulose thin films have been prepared and the cationic celluloses were adsorbed in a similar fashion as in the QCM-D and SPR experiments. Onto these cationic surfaces, fluorescently labeled BSA in different concentrations is deposited by an automatized spotting apparatus and a correlation between the amount of the deposited protein and the fluorescence intensity is established.
- Published
- 2014
- Full Text
- View/download PDF
49. Interaction and enrichment of protein on cationic polysaccharide surfaces.
- Author
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Mohan T, Findenig G, Höllbacher S, Cerny C, Ristić T, Kargl R, Spirk S, Maver U, Stana-Kleinschek K, and Ribitsch V
- Subjects
- Animals, Cattle, Chitosan chemistry, Hydrogen-Ion Concentration, Microscopy, Fluorescence, Wettability, Amines chemistry, Polysaccharides chemistry, Proteins chemistry
- Abstract
In this study, the interaction of fluorescein isothiocyanate functionalized bovine serum albumin (FITC-BSA) with cellulose surfaces decorated with trimethyl chitosan (TMC) is investigated. Two types of TMC, one exhibiting a lower and one with a higher degree of cationization are used for protein adsorption. The adsorption is carried out at different pH values and concentrations of the protein solution. The amount, morphology and wettability of FITC-BSA coating on TMC/cellulose films are determined using quartz crystal microbalance with dissipation (QCM-D), atomic force microscopy, fluorescence microscopy and contact angle measurements. A lower pH and higher concentration of protein solution resulted in a greater amount of irreversibly adsorbed material owing to the reduced solubility and minimized electrostatic repulsion. A maximum adsorption of protein is observed on cellulose surfaces functionalized with TMC carrying a higher degree of cationization compared to TMC with a lower degree of cationization and pure cellulose surfaces at all applied concentrations and pH values. BSA is a commonly used model protein and is applied in this study to better understand its interaction with cationically rendered cellulose surfaces. Such knowledge is essential for creation of multifunctional polysaccharide-based biomaterials., (Copyright © 2014 Elsevier B.V. All rights reserved.)
- Published
- 2014
- Full Text
- View/download PDF
50. Photoregeneration of trimethylsilyl cellulose as a tool for microstructuring ultrathin cellulose supports.
- Author
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Wolfberger A, Kargl R, Griesser T, and Spirk S
- Subjects
- Biopolymers chemistry, Cellulose chemistry
- Abstract
Microstructured thin films based on cellulose, the most abundant biopolymer on Earth, have been obtained by UV-irradiation of acid-labile trimethylsilyl cellulose thin films in the presence of N-hydroxynaphtalimide triflate as photoacid generator. We demonstrate that this photoregeneration process can be exploited for the manufacture of cellulose patterns having feature sizes down to 1 μm, with potential applications in life sciences.
- Published
- 2014
- Full Text
- View/download PDF
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