Cryostructuring of Polymeric Systems. 61. Physicochemical Properties of Poly(vinyl alcohol) Cryogels Prepared on the Basis of Urea-Containing DMSO-Solutions of the Polymer and Evaluation of the Resultant Gel Materials as Potential Drug Carriers

Macroporous physical poly(vinyl alcohol)-based (PVA) cryogels were prepared originating from the dime-thylsulfoxide solutions of the polymer that contained urea additives. The variables of the cryotropic gel-formation process were its temperature and the concentration of the added urea, which caused the increase in the rigidity and heat endurance of the resultant cryogels, as well as promoted widening of the macropores in the gel matter. Subsequent rinsing of the DMSO-swollen cryogels with the water excess resulted in the water-swollen PVA cryogels with simultaneous further increase in their rigidity. These gel matrices were tested with respect of their potential to operate as the polymeric carriers in the drug delivery systems. Loading of such water-swollen cryogels with a model drug, ε-amino caproic acid, and then studies of its release kinetics revealed that urea content in the initial PVA solutions used for the freeze-thaw-induced formation of the DMSO-swollen cryogels played the key role for the release characteristics of the drug-loaded water-swollen gel carrier. Namely, PVA cryogels prepared in the presence of a higher concentration of urea possessed the larger pores and, as a result, the drug release occurred somewhat faster.