Noncovalent (physical) macroporous poly(vinyl alcohol) cryogels (PVACGs) formed by the freezing–defrosting technique without the use of chemical cross-linking reagents are of significant interest as biomedical materials. For their safe use in medicine, it is necessary to ensure reliable sterility of the corresponding processes and products. In this study, PVACGs are prepared by freezing 100 g/L aqueous solutions of this polymer at –20°C for 12 h followed by defrosting at a heating rate of 0.03°C/min. Then, the resulting cryogels are treated with 1–4 N solutions of strong mineral acids (HCl, H2SO4, and H3PO4) and both the character of changes in the physicochemical properties and microstructure of the gel matrix caused by the action of these acids, as well as the possibility of their use for the sterilization of PVACGs, are assessed. It has been shown that HCl solutions cause significant swelling and softening of the gel matrix up to its complete dissolution in 4 N HCl. On the contrary, the treatment of the cryogels with aqueous solutions of H2SO4 or H3PO4 leads to an increase in the elasticity and heat endurance of these cryogels. Tests of the sterilizing properties of such acidic solutions with respect to the cells of microorganisms (bacteria, yeasts, mycelial fungi) incorporated into the cryogels have revealed the high efficiency of this approach, which is attractive especially from the viewpoints of both the simplicity of the treatment itself and the financial viability in the case of using aqueous solutions of sulfuric acid.
Lozinsky et al. (Wed,) studied this question.