ИСТИНА

Modification of polymers and formation of corresponding polymer-based functional composites in solutions containing pressurized CO2 at hundred bars pressure is extremely promising for many possible applications. Solutions of CO2 in water, i.e. carbonic acid solutions formed under high pressure of CO2 saturating the aqueous phase, are both antimicrobial and biocompatible after decompression. Moreover, they are pronouncedly acidic (pH is below 3) when pressurized and can dissolve polycations, chitosan in particular, but they are also self-neutralizing at atmospheric pressure. Furthermore, they are environmentally safe, and also have a number of other technological advantages (providing one-stage process, sterility of the obtained material, no necessity to get rid of any unwanted solvent traces in the modified product, etc.). We proposed a new method of formation of chitosan composite gels with metal nanoparticles (NPs) in the solutions of carbonic acid that opens up a promising way to create antimicrobial composite products that can be used in biomedical applications: for example, during subsequent preparation by freeze-drying of hemostatic chitosan sponges with additional antimicrobial activity provided by Ag NPs. Another example is a composite gel of chitosan with polymer-stabilized Pt NPs where chitosan will play the role of an antimicrobial agent and Pt NPs will protect against skin inflammation and allergies caused by UV radiation. Themorphology of metal-containing chitosan gels, obtained in the solutions of carbonic acid under high pressure was examined by SEM, the size and distribution of NPs were studied by TEM, the mechanics was investigated by rheology measurments, the kinetics of reduction of nanoparticles was explored by UV-vis, IR and X-ray photoelectron spectroscopy and X-ray diffraction analysis. Figure 1.The illustration of chitosan-metal composite, its inner structure, the NPs distribution and the kinetics of Ag NPs reduction by chitosan, dissolved in carbonic acid under high pressure. Acknowledgments The reported study was funded by RFBR according to the research project No 19-03-00348 A