Cryostructuring of polymer systems. Proteinaceous wide-pore cryogels generated by the action of denaturant/reductant mixtures on bovine serum albumin in moderately frozen aqueous media

Abstract

Freeze–thaw processing of bovine serum albumin (BSA) aqueous solutions, which contain also the additives of denaturants (urea in this case) and thiol-bearing reductants [cysteine (Cys) in this case] leads to the formation of wide-pore cryogels. The properties and porous morphology of these spongy gel matrices were demonstrated to depend on the initial concentration of all precursors and on the freezing/frozen storage temperature. The optimum conditions for preparing such BSA-based cryogels were found to be as follows: [BSA] = 3–5 g dL⁻¹, [urea] = 0.5–2.0 mol L⁻¹, [Cys] = 0.01 mol L⁻¹, and freezing temperatures in the range of −15 to −20 °C. The size of gross pores in thus prepared cryogels is ∼50–150 μm. The spatial network of BSA-cryogels was shown to be cross-linked chemically via interchain disulfide bridges. The significant role of hydrophobic interactions in the stabilization of 3D networks of these cryogels is inferred, as well as the supposition about the relay-race sequence mechanism of the intermolecular disulfide cross-link formation is made.