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In this work, surfaces of casted silicone sheets and silicone tubes were functionalized with colloidal polysaccharide complexes (chitosan, carboxymethyl chitosan, and hyaluronic acid in combination with a lysine-based surfactant) in order to introduce antimicrobial and antifouling surface properties. The surface chemistry and morphology, as well as the chemical and mechanical stability of the coatings were characterized. For this purpose, different microscopic and spectroscopic methods, pH-potentiometric titrations and standard methods for evaluation of mechanical properties were used. Finally, the antimicrobial and antifouling properties of functionalized silicone materials were evaluated in vitro. The findings of the physicochemical characterization showed that a discontinuous 3-step dip-coating process can be successfully implemented to coat casted polydimethylsiloxane sheets and tubes with colloidal polysaccharide complexes. These coatings exhibit slow-release leaching in aqueous environment at pH 4.5, 7, and 8 and show very good stability against mechanical abrasion, thus displaying high stability potential during catheter insertion. The antimicrobial properties against gram-positive bacteria, gram-negative bacteria and fungi, showed inhibition of bacterial growth of up to 86%. Furthermore, the bacterial biofilm formation tests have revealed that the hyaluronic acid-surfactant coating exhibits high biofilm growth reduction.

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 + Me 3 Cl groups: 0.27 and 0.64) irreversibly adsorb on the fibers as proven by charge reversal (−12 to +7 mV 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.

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.

The use of biomass to produce value-adding materials is a core objective of the circular economy, which has attracted great research interest in recent decades. In this context, we present here a simple dispersion-casting process for consolidation of cellulose nanofibrils (CNF), lignosulphonate (LS)-rich bio-waste and CaCl2 in composite membranes. The addition of CaCl2 to CNF and LS dispersions reduces the ζ potential, due to an electrostatic screening, which promotes the aggregation of CNF, increases its moisture content and promotes LS deposition on CNFs already in the dispersion phase. Addition of both the LS and CaCl2 to CNF dispersion has an adverse effect on the mechanical properties of the final membranes. The effectiveness of the new composite membranes has been described in terms of their passive (charring) flame retardancy and 100 % UVA/UVB shielding capacity, both identified for membranes with the highest LS content, as well as high electronic resistance.

Chitosan (CS) and trimethyl chitosan (TMC) solutions, as well as nanoparticles synthesized by ionic gelation method are studied. Their characterization is focused on determining the charge and antimicrobial properties against common pathogenic microorganisms and Lactobacillus spp., usually found in resident microbiota of vaginal and gastrointestinal tract. Special emphasis is given to the evaluation of antimicrobial activity in relation to the available cationic charge and the presence of nano-sized chitosan in comparison with chitosan macromolecules. In order to investigate the chitosan's antimicrobial mode of action diffusion nuclear magnetic resonance (D-NMR) is used as a novel approach. This technique enables the monitoring of chitosan nanoparticles (CSNP) effects onto healthy Lactobacillus cells. D-NMR results indicate that CSNP interact with the membrane of Lactobacillus cells, causing the perturbation of the membrane wall and lead to the death of the cells, suggesting the mechanism of Lactobacillus inhibition caused by CSNP. Lactobacillus inhibition is also reflected in low minimal inhibitory concentration (MIC).

This study presents a simple and straightforward method for the preparation of aqueous-based stable polysaccharide-metal oxide nanoparticles composites — composed of carboxymethyl cellulose (CMC) and titanium dioxide nanoparticles (TiO2 NPs), and their interaction with the cellulose surface, is presented. Using a combination of anionic polysaccharide CMC as a stabilizer agent and ultrasound probe sonication technique as an agitation tool, a highly stable dispersion of CMC/TiO2 NPs composites is prepared in water, with and without the presence of calcium chloride electrolyte, at various pH values. The results of the dynamic light scattering and the zeta-potential measurements showed that the quality, the stability of the dispersions and the hydrodynamic radius of the particles (ca, 200–300 nm) remain well-preserved for several weeks under normal storage conditions. The transmission electron microscope revealed that the morphology and size of the dry particles size (ca. 25–50 nm) remain unchanged and are not influenced by the addition of the stabilizer CMC, the electrolyte or the pH value of the solution. The presence of electrolyte and the low pH of the dispersions strongly favored an irreversible and enhanced deposition of CMC/TiO2 NPs on cellulose surface as showed by a quartz crystal microbalance with dissipation. A linear correlation between the concentration of CMC and the adsorbed mass of polymer and NPs, and the water content of the adsorbed layers is observed. X-ray photoelectron spectroscopy and atomic force microscopy are combined to prove the successful immobilization of polymer and NPs on the cellulose surface. The knowledge gained from this study can be extended not only for the stabilization of various metal oxide nanoparticles but also for the development of green polymer/NPs composites, that may have the potential to be used as functional coatings in biomedical (e.g. wound dressing) applications.

The optimized preparation of novel electrospun nanofibrous composites from cellulose acetate (CA) and ultra-high silica zeolites (UHSZ) are reported as a promising material for the adsorption of Volatile Organic Compound (VOCs). Two types of UHSZs, i.e. silicalite and USY were prepared by hydrothermal crystallization while the fabrication of composites was performed using single needle and needle-less electrospinning systems, demonstrating the scalability of the composite fibres’ manufactured. Herein, factors such as properties of spinning solutions and electrospinning process parameters were studied, as well as interactions between the CA and UHSZs. In addition, Quartz Crystal Microbalance - Dissipation technique (QCM-D) was employed with an aim to study the adsorption behaviour of newly developed composites using ammonia as a model pollutant. The QCM-D data revealed that the presence of UHSZs in the CA materials increased adsorption capacity, designating CA/UHSZ composites as potential materials suitable for a large-scale removal of VOCs from polluted air.

With the aim of develop new materials for active food packaging, composites of low-density polyethylene (LDPE) with chitosan (CS) or chitosan sodium montmorillonite clay nanocomposites (CSnano), with or without Irganox 1076 commercial synthetic antioxidant or vitamin E (VE) as natural antioxidant were prepared by melt processing. The obtained materials have been characterized by processing behavior, mechanical and thermal properties, positive groups determination, atomic force microscopy and standard tests to assess antimicrobial and antioxidant activities. The compositions assuring insignificant decrease in mechanical and thermal properties were selected as LDPE/3CSnano/VE and LDPE/6CSnano/VE. It has been shown the chitosan imparts antimicrobial properties to LDPE films while the vitamin E increased the oxidation induction period, especially for materials containing chitosan nanocomposites. The incorporation of both chitosan nanocomposites and vitamin E in polyethylene gave films with good antimicrobial and thermal properties because of significant increase of charge surface and important changes in surface topology and antimicrobial activity because of a synergistic effect. The nanocomposites cannot only passively protect the food against environmental factors, but they may enhance shelf life of food products. (C) 2013 Elsevier Ltd. All rights reserved.

During the last decade xylans were widely researched and several derivatives have been developed and analyzed. However, the application properties of these new products are still sparsely known. The main objective of the presented investigation was to examine whether sulfated xylans from different sources (hard wood and oat-spelt) possess antithrombotic properties and how their protonation/deprotonation behavior in water solutions influence these properties. Two types of xylans, glucuronoxylan derived from beech wood, and arabinoxylan from oat spelt, were sulfated. Infrared spectroscopy, elemental analysis, NMR and size exclusion chromatography were applied for analyzing the success of derivatization. Deprotonation/protonation behavior of xylan samples in water solutions was analyzed by titration methods and the antithrombotic properties were investigated using activated partial thromboplastin time determination. The results showed significant increases in negative charges for the sulfated samples, which were a consequence of introducing sulfated groups as strong acids. However, the increase of antithrombotic properties was not influenced only by the presence of certain amounts of sulfate functional groups but also by the total negative-charges originating from both sulfate and carboxyl groups. The later was proved by the high linear correlation between the activated partial thromboplastin time values, and the total charge of the samples.

The protonation of cotton fabric with irreversibly adsorbed medical chitosan (CO–CT) was measured in aquatic medium at 0.1 M ionic strength by means of potentiometric titrations, and compared with the results obtained for pure cotton and chitosan. For CO–CT, the charging isotherm exhibits a charge reversal around pH � 6:0, which is identified as the point of zero charge (PZC). The pure chitosan and the acid fraction that is present in cotton, protonate according to the one-pK model, with pK CT ¼ 6:3 and pK CO ¼ 4:7, respectively. At pH > PZC, the charge of the acid fraction in CO–CT is negative and constant, and the proton binding is attributed purely to the adsorbed chitosan. On the other hand, the cottonbound acid exhibits a more complex protonation mechanism in CO–CT than in the pure fabric, which is evidenced as an excess positive charge at pH < PZC and a deviation from the one-pK behavior.