Publications by authors named "Rupert Kargl"

35 Publications

Succinylation of Polyallylamine: Influence on Biological Efficacy and the Formation of Electrospun Fibers.

Polymers (Basel) 2021 Aug 24;13(17). Epub 2021 Aug 24.

Laboratory for Characterisation and Processing of Polymers, Faculty of Mechanical Engineering, University of Maribor, Smetanova 17, 2000 Maribor, Slovenia.

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 and . 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.
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http://dx.doi.org/10.3390/polym13172840DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8433649PMC
August 2021

Influence of Charge and Heat on the Mechanical Properties of Scaffolds from Ionic Complexation of Chitosan and Carboxymethyl Cellulose.

ACS Biomater Sci Eng 2021 08 15;7(8):3618-3632. Epub 2021 Jul 15.

Institute of Chemistry and Technology of Biobased System (IBioSys), Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria.

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.
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http://dx.doi.org/10.1021/acsbiomaterials.1c00534DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8396805PMC
August 2021

Water-based carbodiimide mediated synthesis of polysaccharide-amino acid conjugates: Deprotection, charge and structural analysis.

Carbohydr Polym 2021 Sep 20;267:118226. Epub 2021 May 20.

Institute of Chemistry and Technology of Biobased System (IBioSys), Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria; Institute of Automation, Faculty of Electrical Engineering and Computer Science, University of Maribor, Koroška cesta 46, 2000 Maribor, Slovenia. Electronic address:

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: H, C- DEPT 135, H- 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.
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http://dx.doi.org/10.1016/j.carbpol.2021.118226DOI Listing
September 2021

Anticoagulant Activity of Cellulose Nanocrystals from Isora Plant Fibers Assembled on Cellulose and SiO Substrates via a Layer-by-Layer Approach.

Polymers (Basel) 2021 Mar 18;13(6). Epub 2021 Mar 18.

Institute for Chemistry and Technology of Biobased Systems (IBioSys), Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria.

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) 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 SiO 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.
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http://dx.doi.org/10.3390/polym13060939DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8003298PMC
March 2021

Protein repellent anti-coagulative mixed-charged cellulose derivative coatings.

Carbohydr Polym 2021 Feb 25;254:117437. Epub 2020 Nov 25.

Institute for Chemistry and Technology of Biobased Systems, Graz University of Technology, Stremayrgasse 9, A-8010, Graz, Austria.

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.
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http://dx.doi.org/10.1016/j.carbpol.2020.117437DOI Listing
February 2021

Comparison of Trimethylsilyl Cellulose-Stabilized Carbonate and Hydroxide Nanoparticles for Deacidification and Strengthening of Cellulose-Based Cultural Heritage.

ACS Omega 2020 Nov 6;5(45):29243-29256. Epub 2020 Nov 6.

Laboratory for Characterization and Processing of Polymers, Faculty of Mechanical Engineering, University of Maribor, Smetanova Ulica 17, 2000 Maribor, Slovenia.

Herein, colloidal dispersions of alkaline nanoparticles (NPs: CaCO and Mg(OH)) 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 CaCO coatings are superior to Mg(OH) 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.
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http://dx.doi.org/10.1021/acsomega.0c03997DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7676302PMC
November 2020

How can we understand the influence of nanoparticles on the coagulation of blood?

Nanomedicine (Lond) 2020 08 17;15(20):1923-1926. Epub 2020 Jul 17.

Institute for Chemistry & Technology of Biobased Systems (IBIOSYS), Graz University of Technology, Stremayrgasse 9, Graz, 8010, Austria.

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http://dx.doi.org/10.2217/nnm-2020-0177DOI Listing
August 2020

Chemical Structure-Antioxidant Activity Relationship of Water-Based Enzymatic Polymerized Rutin and Its Wound Healing Potential.

Polymers (Basel) 2019 Sep 26;11(10). Epub 2019 Sep 26.

Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria.

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 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 O•, NO•, and OH•, and (iii) chelate Fe. The influence of PR on fibroblast and HaCaT cell viability was evaluated to confirm the applicability of water soluble PR for wound healing application.
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http://dx.doi.org/10.3390/polym11101566DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6835416PMC
September 2019

Affinity of Serum Albumin and Fibrinogen to Cellulose, Its Hydrophobic Derivatives and Blends.

Front Chem 2019 6;7:581. Epub 2019 Sep 6.

Laboratory for Characterization and Processing of Polymers, Faculty of Mechanical Engineering, University of Maribor, Maribor, Slovenia.

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 bovine serum albumin (BSA) and 0.1 and 1 mg mL 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.
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http://dx.doi.org/10.3389/fchem.2019.00581DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6743410PMC
September 2019

Functional dextran amino acid ester particles derived from N-protected S-trityl-L-cysteine.

Colloids Surf B Biointerfaces 2019 Sep 4;181:561-566. Epub 2019 Jun 4.

Laboratory for Characterization and Processing of Polymers (LCPP), Faculty of Mechanical Engineering, University of Maribor, Smetanova ulica 17, SI-2000, Maribor, Slovenia; Institute of Paper, Pulp and Fibre Technology (IPZ), Graz University of Technology, Inffeldgasse 23, A - 8010, Graz, Austria. Electronic address:

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 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.
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http://dx.doi.org/10.1016/j.colsurfb.2019.06.005DOI Listing
September 2019

Estimation of the magnitude of quadrupole relaxation enhancement in the context of magnetic resonance imaging contrast.

J Chem Phys 2019 May;150(18):184306

Institute of Medical Engineering, Graz University of Technology, Stremayrgasse 16 / III, A-8010 Graz, Austria.

Magnetic Resonance Imaging (MRI) is one of the most powerful diagnostic tools providing maps of 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 for 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 (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.
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http://dx.doi.org/10.1063/1.5082177DOI Listing
May 2019

Nano- and Micropatterned Polycaprolactone Cellulose Composite Surfaces with Tunable Protein Adsorption, Fibrin Clot Formation, and Endothelial Cellular Response.

Biomacromolecules 2019 06 29;20(6):2327-2337. Epub 2019 May 29.

Laboratory for Characterisation and Processing of Polymers, Faculty of Mechanical Engineering , University of Maribor , Smetanova ulica17 , 2000 Maribor , Slovenia.

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.
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http://dx.doi.org/10.1021/acs.biomac.9b00304DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6750646PMC
June 2019

Chitin nanowhisker - Inspired electrospun PVDF membrane for enhanced oil-water separation.

J Environ Manage 2018 Dec 15;228:249-259. Epub 2018 Sep 15.

International and Inter University Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, 686560, Kerala, India. Electronic address:

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.
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http://dx.doi.org/10.1016/j.jenvman.2018.09.039DOI Listing
December 2018

Nanofibrous polysaccharide hydroxyapatite composites with biocompatibility against human osteoblasts.

Carbohydr Polym 2017 Dec 30;177:388-396. Epub 2017 Aug 30.

University of Maribor, Faculty of Mechanical Engineering, Laboratory for Characterisation and Processing of Polymers, Smetanova 17, SI-2000 Maribor, Slovenia.

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.
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http://dx.doi.org/10.1016/j.carbpol.2017.08.111DOI Listing
December 2017

Multilayered Polysaccharide Nanofilms for Controlled Delivery of Pentoxifylline and Possible Treatment of Chronic Venous Ulceration.

Biomacromolecules 2017 Sep 22;18(9):2732-2746. Epub 2017 Aug 22.

University of Maribor , Faculty of Medicine, Institute of Biomedical Sciences, Taborska ulica 8, SI-2000 Maribor, Slovenia.

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 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.
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http://dx.doi.org/10.1021/acs.biomac.7b00523DOI Listing
September 2017

Nonspecific protein adsorption on cationically modified Lyocell fibers monitored by zeta potential measurements.

Carbohydr Polym 2017 May 25;164:49-56. Epub 2017 Jan 25.

Institute for Chemistry and Technology of Materials, Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria; CD-Laboratory for Fiber Swelling and Paper Performance, Inffeldgasse 23(A), 8010 Graz, Austria; Laboratory for Characterization and Processing of Polymers (LCPP), University of Maribor, Smetanova 17, 2000 Maribor, Slovenia; Institute for Paper, Pulp and Fiber Technology, Inffeldgasse 23, 8010 Graz, Austria. Electronic address:

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 NMeCl 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.
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http://dx.doi.org/10.1016/j.carbpol.2017.01.088DOI Listing
May 2017

Synthesis and film formation of furfuryl- and maleimido carbonic acid derivatives of dextran.

Carbohydr Polym 2017 Apr 26;161:1-9. Epub 2016 Dec 26.

Center of Excellence for Polysaccharide Research, Institute for Organic Chemistry and Macromolecular Chemistry, Friedrich Schiller University of Jena, Humboldtstraße 10, D-07743 Jena, Germany. Electronic address:

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.
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http://dx.doi.org/10.1016/j.carbpol.2016.12.038DOI Listing
April 2017

Interaction of Tissue Engineering Substrates with Serum Proteins and Its Influence on Human Primary Endothelial Cells.

Biomacromolecules 2017 02 24;18(2):413-421. Epub 2017 Jan 24.

Institute for Chemistry and Technology of Materials, Graz University of Technology , Stremayrgasse 9, 8010 Graz, Austria.

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.
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http://dx.doi.org/10.1021/acs.biomac.6b01504DOI Listing
February 2017

Exploring Nonspecific Protein Adsorption on Lignocellulosic Amphiphilic Bicomponent Films.

Biomacromolecules 2016 Mar 18;17(3):1083-92. Epub 2016 Feb 18.

Institute for Chemistry and Technology of Materials, Graz University of Technology , Stremayrgasse 9, 8010 Graz, Austria.

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.
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http://dx.doi.org/10.1021/acs.biomac.5b01700DOI Listing
March 2016

Photolithographic patterning of cellulose: a versatile dual-tone photoresist for advanced applications.

Cellulose (Lond) 2015;22(1):717-727. Epub 2014 Oct 16.

Chair of Chemistry of Polymeric Materials, University of Leoben, Otto Glöckel-Straße 2, 8700 Leoben, Austria.

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.
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http://dx.doi.org/10.1007/s10570-014-0471-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4579862PMC
October 2014

Designing Hydrophobically Modified Polysaccharide Derivatives for Highly Efficient Enzyme Immobilization.

Biomacromolecules 2015 Aug 31;16(8):2403-11. Epub 2015 Jul 31.

βInstitute for Engineering Materials and Design, University of Maribor, Smetanova 17, 2000 Maribor, Slovenia.

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.
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http://dx.doi.org/10.1021/acs.biomac.5b00638DOI Listing
August 2015

Antifouling coating of cellulose acetate thin films with polysaccharide multilayers.

Carbohydr Polym 2015 Feb 26;116:149-58. Epub 2014 Apr 26.

Institute of Chemistry, Karl-Franzens-University Graz, Heinrichstraße 28, 8010 Graz, Austria.

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).
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http://dx.doi.org/10.1016/j.carbpol.2014.04.068DOI Listing
February 2015

Interaction and enrichment of protein on cationic polysaccharide surfaces.

Colloids Surf B Biointerfaces 2014 Nov 5;123:533-41. Epub 2014 Oct 5.

Institute for Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria.

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.
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http://dx.doi.org/10.1016/j.colsurfb.2014.09.053DOI Listing
November 2014

Photoregeneration of trimethylsilyl cellulose as a tool for microstructuring ultrathin cellulose supports.

Molecules 2014 Oct 10;19(10):16266-73. Epub 2014 Oct 10.

Institute for the Engineering and Design of Materials, University of Maribor, Smetanova Ulica 17, 2000 Maribor, Slovenia.

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.
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http://dx.doi.org/10.3390/molecules191016266DOI Listing
October 2014

Triggering protein adsorption on tailored cationic cellulose surfaces.

Biomacromolecules 2014 Nov 8;15(11):3931-41. Epub 2014 Oct 8.

Institute for Chemistry, University of Graz , Heinrichstrasse 28, 8010 Graz, Austria.

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.
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http://dx.doi.org/10.1021/bm500997sDOI Listing
November 2014

Cationically rendered biopolymer surfaces for high protein affinity support matrices.

Chem Commun (Camb) 2013 Dec;49(98):11530-2

University of Maribor, Institute for the Engineering and Design of Materials, Smetanova Ulica 17, 2000 Maribor, Slovenia.

The use of cationic biopolymer surfaces for high protein binding affinity matrices is described. As model proteins, fluorescently labeled bovine serum albumins (FITC-BSA, TRITC-BSA) have been employed. The amount of proteins on such cationically rendered surfaces was quantified by QCM-D. In addition, flexible, transparent, patterned COP slides have been prepared and loaded with proteins ranging from 15 pM to 15 μM TRITC-BSA.
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http://dx.doi.org/10.1039/c3cc46414hDOI Listing
December 2013

Interaction and structure in polyelectrolyte/clay multilayers: a QCM-D study.

Langmuir 2013 Jul 25;29(27):8544-53. Epub 2013 Jun 25.

Division of Surface and Interface Science, Institute of Chemistry, Karl-Franzens-University Graz, Heinrichstrasse 28, A-8010 Graz, Austria.

This study focuses on the investigation of the influence of the ionic strength on the internal structure, film forming behavior, and swelling properties of polyelectrolyte/clay multilayers. Layer-by-layer films were prepared with three different polyelectrolytes [polyethylenimine (PEI), polydiallyldimethylammoniumchloride (pDADMAC), and 2-hydroxy-3-trimethylammonium propyl chloride starch (HPMA starch)] in combination with laponite clay platelets on three different surfaces. All experiments were carried out at two different ionic strengths (30 mM or 500 mM NaCl). The experiments performed with strong polyelectrolytes revealed a higher film thickness and adsorbed masses of clay and polyelectrolyte at 500 mM NaCl. The films containing PEI showed different behavior and were considerably less sensitive to changes in the ionic strength. This was also reflected by the swelling behavior as demonstrated by quartz crystal microbalance with dissipation (QCM-D) measurements. Films comprising PEI showed, in contrast to the other polyelectrolytes, much lower swelling in water leading to more compact and stable films in humid environments which is important for numerous applications of LbL clay coatings.
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http://dx.doi.org/10.1021/la400880aDOI Listing
July 2013

Chitosan-silane sol-gel hybrid thin films with controllable layer thickness and morphology.

Carbohydr Polym 2013 Mar 27;93(1):285-90. Epub 2012 Apr 27.

Karl-Franzens-Universität Graz, Institut für Chemie, Heinrichstrasse 28/III, 8010 Graz, Austria.

The preparation of thin films of chitosan-silane hybrid materials by combining sol-gel processing and spin coating is reported. A variety of silanes can be used as starting materials for the preparation of such thin films, namely tetraethoxysilane, tri-tert-butoxysilanol, trimethylethoxysilane, p-trifluoromethyltetra-fluorophenyltriethoxysilane, trivinylmethoxysilane, (methoxymethyl)trimethyl-silane, and hexamethoxydisilane. These silanes are subjected to a sol-gel process before they are added to acidic chitosan solutions. The chitosan:silane ratio is kept constant at 6:1 (w/w) and dilutions with ethanol are prepared and spin coated. Depending on the degree of dilution, film thickness can be controlled in a range between 5 and 70 nm. For the determination of additional surface properties, static water contact angle measurements and atomic force microscopy have been employed.
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http://dx.doi.org/10.1016/j.carbpol.2012.04.030DOI Listing
March 2013

Enzymatic digestion of partially and fully regenerated cellulose model films from trimethylsilyl cellulose.

Carbohydr Polym 2013 Mar 25;93(1):191-8. Epub 2012 Feb 25.

Laboratory for Characterization and Processing of Polymers, Faculty of Mechanical Engineering, University of Maribor, Smetanova 17, SI-2000 Maribor, Slovenia.

Partially and fully regenerated cellulose model films from trimethylsilyl cellulose (TMSC) were prepared by a time dependent regeneration approach. These thin films were characterized with contact angle measurements and attenuated total reflectance infrared spectroscopy (ATR-IR). In order to get further insights into the completeness of the regeneration we studied the interaction of cellulase enzymes from Trichoderma viride with the cellulose films using a quartz crystal microbalance with dissipation (QCM-D). To support the results from the QCM-D experiments capillary zone electrophoresis (CZE) and atomic force microscopy (AFM) were applied. The changes in mass and energy dissipation due to the interaction of the enzymes with the substrates were correlated with the surface wettability and elemental composition of the regenerated films. The highest interaction activity between the films and the enzyme, as well as the highest cellulose degradation, was observed on fully regenerated cellulose films, but some degradation also occurred on pure TMSC films. The enzymatic degradation rate correlated well with the rate of regeneration. It was demonstrated that CZE can be used to support QCM-D data via the detection of enzyme hydrolysis products in the eluates of the QCM-D cells. Glucose release peaked at the same time as the maximum mass loss was detected via QCM-D. It was shown that a combination of QCM-D and CZE together with enzymatic digestion is a reliable method to determine the conversion rate of TMSC to cellulose. In addition QCM-D and AFM revealed that cellulase is irreversibly bound to hydrophobic TMSC surfaces, while pure cellulose is digested almost completely in the course of hydrolysis.
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http://dx.doi.org/10.1016/j.carbpol.2012.02.033DOI Listing
March 2013

Interactions of a cationic cellulose derivative with an ultrathin cellulose support.

Carbohydr Polym 2013 Feb 17;92(2):1046-53. Epub 2012 Oct 17.

Laboratory for Characterization and Processing of Polymers, Faculty of Mechanical Engineering, University of Maribor, Smetanova 17, SI-2000 Maribor, Slovenia.

The adsorption behavior of cellulose-4-[N-methylammonium]butyrate chloride (CMABC) on two hydrophilic substrates is studied, namely nanometric cellulose model thin films and silicon dioxide substrates. The adsorption is quantified in dependence of electrolyte concentration and pH value using a quartz crystal microbalance with dissipation (QCM-D). In case of CMABC, at high ionic strengths (25-100 mM NaCl) high adsorption is observed at pH 7 (Δf(3): -15 to -17 Hz) while at lower ionic strengths (1-10 mM) less CMABC (Δf(3): -2 to -12 Hz) is deposited on the cellulose surfaces as indicated by the frequency changes using QCM-D. A change in pH value from 7 to 8 reveals an increase in adsorption. Atomic force microscopy shows that the coating of cellulose thin films with CMABC changes the morphology from a fibrillar to a particle like structure on the surface. The surface wettability with water increases with an increasing amount of CMABC on the surface compared to neat cellulose model films. At lower pH values (3 and 5), CMABC does not adsorb onto the cellulose model thin films. XPS is used to validate the results and to determine the nitrogen content of the surfaces. In addition, adsorption of CMABC onto another hydrophilic and negatively charged substrate, silicon dioxide coated quartz crystals, cannot be detected at different pH values and electrolyte concentrations as proven by QCM-D.
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http://dx.doi.org/10.1016/j.carbpol.2012.10.026DOI Listing
February 2013
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