By freezing at -20°C for 12 h and then defrosting by heating at a rate of 0.03°C/min of aqueous solutions of polyvinyl alcohol (PVA) without and with 0.1-0.5 mol/L additives of basic α-amino acids (arginine, histidine, lysine, ornithine) in non-protonated or salt forms, macroporous physical (non-covalent) cryogels were prepared and the effect of such additives on the physicochemical properties of the gel materials formed in this way was studied. It has been shown that in relation to the cryotropic gelation of PVA, additives of arginine, its hydrochloride, as well as histidine, exhibit chaotropic activity due to counteracting hydrogen bonding, thus leading to a decrease in the elasticity and heat resistance of the resultant cryogels, whereas additives of lysine, ornithine and their hydrochlorides, as well as histidine hydrochloride, due to the promotion of hydrogen bonding, act as kosmotropic agents, causing an increase in the compressive modulus of elasticity and an increase in the fusion temperature of the samples. The study of the kinetics of release of the amino acid additives used in the work showed that the release of hydrochlorides from the gel carrier into the external aqueous environment occurred somewhat more slowly than that of non-protonated forms, but in all cases without noticeable diffusion difficulties. Considering that such amino acids are used in cosmetology, the results obtained in this study suggest that PVA cryogels loaded with amino acid additives may be of practical interest in the development of carriers for cosmetics such as nourishing masks, coatings for problem areas of the skin, “patches”, etc.
O. Yu. Kolosova (Wed,) studied this question.