ИСТИНА

It is well-known that materials based on chitosan are very promising from the viewpoint of the variety of biomedical applications (protective coatings, drug delivery, bone tissue regeneration implants, etc.), because of the complex of unique properties of this widely available biopolymer, such as biocompatibility, non-toxicity, antimicrobial activity. Usually diluted acetic acid is used to dissolve chitosan, but it is known, that some residuals of this acid in chitosan-containing medical devices or materials could act as promoters of the human allergenic reaction. Therefore it will be very useful to find a biocompatible medium for chitosan dissolution. We propose a novel approach to stabilize antimicrobial metal nanoparticles by biopolymer chitosan dissolved in the unique medium, namely carbonic acid, i.e. in water saturated with carbon dioxide at high pressure. Carbonic acid exhibits certain antimicrobial properties due to the action of CO2 under high pressure. Moreover after the depressurization of CO2 it decomposes spontaneously into gas carbon dioxide and pure water. Therefore carbonic acid is an absolute biocompatible and self-neutralizing medium, which is very promising from the viewpoint of biomedical applications. We showed that one could obtain stable composite chitosan gels (allowing the freeze-drying with keeping their porous morphology) with metal nanoparticles in the solutions of carbonic acid. Moreover these nanoparticles can be effectively reduced by gaseous, biocompatible and also self-neutralizing reduction agent H2, which can be simply admixed to the CO2.