Study of cryostructuring of polymer systems. 42. Physicochemical properties and microstructure of wide-porous covalently cross-linked albumin cryogels

Abstract

Chemically cross-linked wide-porous protein cryogels have been obtained by freezing aqueous bovine serum albumin (BSA) solutions (30–50 g/L) at–15,–20, or–25°C in the presence of water-soluble carbodiimide (CDI) as a coupling agent. It has been shown that the gel-fraction yield and the swelling extent of the polymer phase of the formed spongy matrices depend primarily on the initial concentration of albumin and the amount of CDI added to a system, while the morphometric characteristics of the porous microstructure of the BSA cryogels are mainly determined by the temperature of the cryogenic treatment. The sizes of macropores in the obtained cryogels range from ≈50 to ≈200 μm. A high-sensitivity differential scanning calorimetric study of the conformational state of protein macromolecules incorporated into the spatial network of the polymer phase (gel walls of macropores) of the cryogels has shown that, during the cryotropic gelation, the native structure of albumin globules is subjected to “cold denaturation,” and the partly unfolded conformation of the protein is, simultaneously, fixed by intermolecular covalent cross links.