Adsorption of bovine serum albumin onto radiation-crosslinked poly(acrylamide/acrylic acid)

Abstract

Poly(acrylamide/acrylic acid) (AAm/AAc) hydrogels were prepared at initial acrylic acid compositions of 70, 80 and 85 mol%, respectively. Mixtures of AAm and AAc monomers were irradiated in a Co-60 gamma-ray source at a dosage of 8 kGy. These hydrogels were used in experiments associated with the swelling, diffusion and adsorption of bovine serum albumin (BSA) from aqueous solution. The data obtained allowed the swelling and diffusion parameters for the hydrogels to be calculated. In the BSA adsorption experiments, the adsorption kinetics together with the influence of the pH of the medium, the initial BSA concentration and the composition of the hydrogels on the adsorption efficiency of the AAm/AAc hydrogels were all studied. The rates of BSA adsorption were found to conform to pseudo-first-order kinetics and a kinetic model was used to calculate the corresponding rate constant for the adsorption processes. The adsorption of BSA onto AAm/AAc hydrogels decreased with increasing pH, with the maximum adsorption being observed at a pH value of 3.7. In terms of the Giles classification, the adsorption was of type C. BSA adsorption increased as the AAc content of the hydrogels increased. Significant amounts of adsorbed BSA (up to 95%) were eluted when an elution medium containing 1.0 M NaSCN was employed at a pH value of 8.0.