Novel Functional Hybrid Materials from Renewable Sources

The aim of the project is the preparation of novel functional hybrid materials on the basis of renewable resources. For this purpose, different types of polysaccharides (chitins, chitosans, alginates, arabinoxylans) are subjected to classical sol-gel chemistry using a variety of alkoxysilanes. All used polysaccharides are waste products either in food or paper making industry and cannot be used for nutrition purposes. The use of different fabrication pathways for the hybrid materials allows obtaining materials with different shapes such as nanometric films (spin-coating), nanofibers (electrospinning) and porous materials (supercritical drying). The thickness and diameter of the films and nanofibers is tuned by variation of the viscosity and the concentration of the stock solutions as well as by the molecular weight of the polysaccharides, respectively. The incorporation of silicon compounds into the polysaccharide matrix provides a tuning of the swelling behavior of the materials which is advantageous in respect of later, desired applications in wound dressings and artificial tissues. In addition, a tuning of the wettability can be easily performed due to the choice of hydrophilic, hydrophobic or oleophobic silicon compounds. Besides standard surface analytics (atomic force microscopy, scanningransmission electron microscopy, X-ray photoelectron spectroscopy etc), the materials are investigated in respect to their antimicrobial activity towards different kinds of microorganisms such as staphylococcus aureus, escherichia coli, streptococcus agalensis, candida albicans, candida glabrata. The influence of the silane content, type of alkoxysilane and the surface morphology on the antimicrobial activity is studied in detail. In addition, cell compatibility studies (endothelian cells and fibroblasts) are performed to ensure biocompatibility. For the nanometric films and nanofibers, these tests can be done in situ using a quartz crystal microbalance with dissipation (QCM-D) where the growth and proliferation of e.g. endothelian cells can be monitored online. The QCM-D method is also used to monitor the interaction capacity of the films with proteins, too. In particular, the interaction capacity with fibronectin is of interest due to its key role in the healing of wounds and assimilation of artificial tissues as well as in the differentiation and mitigation of cells. Besides interactions with physiological systems, the nanofibers will be subjected to nano-intendation experiments. These experiments use the tip of an atomic force microscope to distort the nanofibers and to determine the mechanical strength (Young`s modulus) on the nanometer scale. These experiments are carried out using different humidities and in the presence of simulated body fluid to mimic physiological conditions. In the course of these studies, the release of silicon species from the materials is determined by means of induced coupled plasma mass spectrometry.