ИСТИНА

The problem of creation of temporary prostheses, as well as dosage forms with controlled release of active substances based on biodegradable polymers is one of the actual problems of modern medicine. There are at least two questions in the scope of this problem. The first is how to find a “green” way to obtain polymer of the predetermined form containing drugs, cell growth factors, proteins, etc. Another question is how to measure mean and local concentrations of the active substances in the polymers, and how to control the release of the substances in vitro and in vivo. One of the most perspective solutions is using supercritical fluids, first of all, CO2 (scCO2) for impregnation of polymers. Many biodegradable polymers, such as D,L-polylactide, easily swell in it, and active substances can be dissolved or dispersed in scCO2. By varying ways of CO2 removing from polymers different forms may be obtained: solid pieces, foams, micron-size particles without traces of toxic organic solvents. Nitroxides are perspective additives to polymers due to combining biological activity and the ability to control their concentration, mobility, distribution between the polymer phase and biological fluids, etc, by EPR spectroscopy. In the lecture, our experience of using spin probe method of characterization of D,L-polylactide materials of different size and shape (films, foams, micron-size particles) obtained using scCO2, as well as peculiarities of the release of nitroxides of different nature, such as TEMPOL and spin-labelled drugs, is presented. The possibility of obtaining the materials with uniform distribution of nitroxides in polymer matrixes using scCO2 is shown. The features of the local mobility of spin probes in D,L-polylactide caused by intermolecular interactions are discussed. The kinetic curves and other regularities of the nitroxides release from D,L-polylactide films, foams and powders to phosphate buffer solution at 37oC are described. Therefore, the theranostic approach based on impregnation of bioderadable polymers by nitroxides in scCO2 and study of the features of their release seems to be very perspective.