Ultrathin antifouling and antibacterial protective nanocoatings were prepared from ionic derivatives of chitosan using layer-by-layer deposition methodology. The surfaces of silicon, and glass protected by these nanocoatings were resistant to non-specific adsorption of proteins disregarding their net charges at physiological conditions (positively charged TGF-β1 growth factor and negatively charged bovine serum albumin) as well as human plasma components. The coatings also preserved surfaces from the formation of bacterial (Staphylococcus aureus) biofilm as shown using microscopic studies (SEM, AFM) and the MTT viability test. Moreover, the chitosan-based films adsorbed onto glass surface demonstrated the anticoagulant activity towards the human blood. The antifouling and antibacterial actions of the coatings were correlated with their physicochemical properties. The studied biologically relevant properties were also found to be dependent on the thickness of those nanocoatings. These materials are promising for biomedical applications, e.g., as protective coatings for medical devices, anticoagulant coatings and protective layers in membranes.

We report here on synthesis and characterization of novel hybrid material consisting of silver nanoparticles (nAgs) embedded in calcium carbonate microparticles (μ-CaCO3) serving as carriers for sustained release. nAgs are commonly used as antimicrobial agents in many commercial products (textiles, cosmetics, and drugs). Although they are considered to be safe, their interactions with human organisms are still not fully understood; therefore it is important to apply them with caution and limit their presence in the environment. The synthesis of the new material was based on the co-precipitation of CaCO3 and nAg in the presence of poly(sodium 4-styrenesulfonate). Such designed system enables sustained release of nAg to the environment. This hybrid colloidal material (nAg/μ-CaCO3) was characterized by microscopic and spectroscopic methods. The release of nAg from μ-CaCO3 microparticles was followed in water at various pH values. Microbiological tests confirmed the effectiveness of these microparticles as an antibacterial agent. Importantly, the material can be stored as a dry powder and subsequently re-suspended in water without the risk of losing its antimicrobial activity. nAg/μ-CaCO3 was applied here to insure bacteriostatic properties of down feathers that may significantly prolong their lifetime in typical applications. Such microparticles may be also used as, e.g., components of coatings and paints protecting various surfaces against microorganism colonization.Electronic supplementary materialThe online version of this article (doi:10.1007/s11051-012-1313-7) contains supplementary material, which is available to authorized users.

One-component'' chitosan-based multilayer films have been formed and characterized for the first time. Two derivatives of chitosan containing oppositely charged strong ionic groups were synthesized for that purpose. Low molecular weight chitosan was modified by glycidyltrimethylammonium chloride to obtain the cationic form (CCh) of the polymer. The anionic form of chitosan (ACh) was obtained by sulfonation of carboxymethylchitosan with trimethylamine-sulfur trioxide. The two derivatives of chitosan were used to prepare stable multilayer polyelectrolyte films through a layer-bylayer (LbL) deposition technique. The films revealed smooth surfaces and linear growth of the thickness during LbL adsorption as measured by atomic force microscope (AFM). Contact angle measurements revealed a very hydrophilic nature of the formed films. In contrast, the hybrid films, made of one of the chitosan derivatives and the synthetic oppositely charged polyelectrolyte, demonstrated non-linear growths and much higher surface roughnesses. So far, the multilayer films built of natural polymers like chitosan and alginate as well as the mentioned hybrid films have shown difficulties in regular formation related to the differences in polymer backbones and/or the charge distribution along them. The approach proposed here omits the inherent entropic barrier and leads to the controlled formation of robust ''one-component'' multilayer films. The entropy-driven formation of such films was also supported by the calorimetric studies on the model polyelectrolyte complexes in solution. Thanks to biocompatibility and bacteriostatic properties of chitosan and its derivatives, CCh/ACh multilayer films may be potentially useful for many biomedical and environmental protection applications.

No abstract

Biodegradation of new polymer foundry binders composition of poly(acrylic acid)/dextrin **) Summary -Investigations were carried out focusing on novel polymeric binders and their susceptibility to biodegradation. As an example a water-soluble composition of poly(acrylic acid)/dextrin is presented. Determination of the total oxygen demand for biodegradation has been accomplished under laboratory conditions, in accordance with the static water test system (the Zahn-Wellens method). In that system the mixture in which the biodegradation takes place contains activated sludge as the inorganic nutrient and the investigated polymeric composition designed to be the exclusive source of carbon and energy. The progressively increasing biodegradation has been tested by means of the chemical oxygen demand and by the simultaneously determined degree of biodegradation R t . These investigations have proven the poly(acrylic acid)/dextrin composition to be a material fully biodegradable in water. This statement is justified by degree of biodegradation R t = 65 % which occurred on the 28th day of testing. At the same time a separate sample of the crosslinked polymeric composition was tested on the biodegradation resulting from storing the sample for over 6 months in garden soil. During that time several analyses were performed by means of the Raman spectroscopy, optical microscopy and atomic force microscopy (AFM). The intention was to study structural changes on surfaces resulting from the degradation.

The formation of ultrathin chitosan-based nanocoating on HL-60 model cells and their protective function in hypothermic storage are presented. HL-60 cells are encapsulated in ultrathin shells by adsorbing cationic and anionic chitosan derivatives in a stepwise, layer-by-layer, procedure carried out in an aqueous medium under mild conditions. The chitosan-based films are also deposited on model lipid bilayer and the interactions are studied using ellipsometry and atomic force microscopy. The cells covered with the chitosan-based films and stored at 4 °C for 24 h express viability comparable to that of the control sample incubated at 37 °C, while the unprotected cells stored under the same conditions do not show viability. It is shown that the chitosan-based shell protects HL-60 cells against damaging effect of hypothermic storage. Such nanocoatings provide protection, mechanical stability, and support the cell membrane, while ensuring penetration of small molecules such as nutrients/gases what is essential for cell viability.

The control of the morphology, as well as the physical and chemical properties, of nanopores is a key issue for many applications.