ANTIBACTERIAL POLYURETHANE-BASED COMPOSITES: STRUCTURE, PROPERTIES AND BEHAVIOURS

Numerous medical devices used for medical practice are inserted into the human body for short periods of time or destined to remain in place permanently. Once inserted, however, they could stimulate the development of an ideal environment for pathogenic bacteria and give rise to resilient infections. The object of this research project was the study and the development of innovative materials for the realization of biomedical devices with antibacterial functions. In this work, polyurethane-based composites, containing different antibacterial functions introduced by processing techniques (melt compounding) or post-processing (coatings) were prepared and characterized. TGA, FTIR, SEC, UV, AFM, Contact Angle, Mechanical Tests, Rheology have been performed to investigate the prepared composites. Microstructural characterization of TPU-based starting material was investigated by 1H and 13C NMR spectroscopy highlighting the chemical composition of the monomers and the comonomer sequences. Molecular investigations of finished materials indicates a decrease in the polymer molecular weights after the compounding. For samples loaded with chitosan and silver a slight reduction was registered, whereas the presence of TiO2 determined a marked reduction of the molecular weights. TiO2, in the form of anatase, exhibiting a catalytic photo activity, which enhanced sterilization capabilities beside the generation of hydroxyl radicals capable of degrading the polymer matrix, as evidenced in TGA experiments. Mechanical properties of composites materials, measured by carrying out tensile tests, showed slight differences in Young modulus, tensile strength and elongation at break when compared to the homopolymer, with the exception of TiO2-based composite which resulted more brittle. Similar rheological behaviors were observed for composites and the homopolymer, performing frequency sweep experiments. The antibacterial activities of the composite materials were evaluated by comparing the behavior of composite surfaces exposed to two different types of bacterial strains. The observed results show a variable activity depending on the bacterial strains used. The most promising results concern the activity towards S. aureus for which, in some cases, a reduction of 50% bacterial proliferation was observed in only 24 hours (Figure 1). Summarizing, the whole data confirm a possible inexpensive introduction of the investigated fillers at industrial scale, especially considering the promising antibacterial activities observed for such composites.