INVESTIGATION OF THE EFFECT OF PROCESSING ALLOGENEIC AND XENOGENIC BIOMATERIALS IN SUB- AND SUPERCRITICAL CARBON DIOXIDE ON THE ABILITY TO SUPPRESS CALCIFICATION

Highlights Hybrid decellularization of allografts in scCO 2 with a small addition of the detergent Tween 80 is very effective in terms of reducing calcification. A special coating based on chitosan nanoparticles obtained and applied from the water/subcritical CO 2 system makes it possible to significantly reduce calcification of the standard GA-stabilized pericardium. Aim. To conduct a comparative analysis of anticalcification properties of implants based on allo- and xeno-tissue after treatment in super- (scCO 2 ) and subcritical carbon dioxide. Methods. We have performed a modification of the following structures: a) rat vessels by hybrid decellularization in scCO 2 with detergents b) calf pericardium by direct coating of chitosan nanoparticles with silver from the water/carbon dioxide system under pressure (carbonic acid). Following that we have performed an in vivo calcification study on rats (n = 10 for each type of sample). To model the behavior of biomaterial in the human body, we have implanted allogeneic modified aorta into rats. To determine the calcium in the extracted samples, we have used spectrophotometric method to estimate the concentration of calcium. To assess the cytotoxicity of nanocoated pericardium samples, we have measured the impedance of cells populated on biomaterial samples was used. Results. The treatment of rat vessels in supercritical CO 2 reduces the deposition of calcium salts by 30% compared to baseline allografts. Pericardium coated with chitosan nanoparticles can be characterized by a significant decrease in calcification – the biomatrix coated with Cht_Ag/TPP contains only (0.015 ± 0.005) wt.% of calcium salts, which is significantly lower compared with GA-stabilized pericardium with (0.070 ± 0.015) wt.% after the experiment. Biocomposites with nanocoating are characterized by similar cellular index compared to a sample of uncoated xeno-tissue. All samples exhibit a cytostatic effect, including nanocoated samples (Cht_Ag/TPP), which proves the encapsulation of silver in the polymer matrix and ensures the absence of negative effects on the body during normal functioning. The coating of biomatrix based on hollow chitosan nanoparticles contributes to an increase in cell proliferation. Conclusion. The use of supercritical technology for the purification of biomaterials, as well as the creation and application of polymer protective coatings in order to enhance the ability to suppress calcification looks very promising. At the same time, the use of such a “green” approach to the modification of bioprostheses is a more advantageous strategy relative to the standard generally accepted methods of their chemical modification.