Mechanism and characteristics of protein release from lactitol-based cross-linked hydrogel

Lactitol-based cross-linked hydrogel was synthesized, and model proteins (α-chymotrypsin, β-lactoglobulin, bovine serum albumin (BSA), and γ-globulin) were incorporated into the cross-linked hydrogel. The larger-molecular-weight proteins have lower diffusivity (D(e)) in the hydrogel. Increasing temperature accelerated the diffusion rate of proteins; however, the diffusion did not follow the Arrhenius equation at temperatures above 37 °C. The swelling ratio of the hydrogel was slightly decreased after heating for 2 h at 37 and 45 °C, and significantly reduced after 1 h at 60 °C. Therefore, diffusion of β-lactoglobulin and BSA may be decreased by hydrogel shrinking at temperature over 37 °C. The model proteins have high affinities to buffer solution compared to the hydrogel network structure, resulting in high partition coefficients (K > 1) which do not affect the calculation of D(e) values. Incorporated protein release follows the theory of hindered diffusion.