PREPARATION, CHARACTERIZATION, AND ALBUMIN ADSORPTION OF AMPHOTERIC POLYMER LATTICES

Amphoteric polymer latices were prepared by Hofmann reaction of styrene/acrylamide (AAm) copolymer (P(St/AAm)) latex, i.e. by treating P(St/AAm) latex with sodium hypochlorite (NaOCl) and sodium hydroxide (NaOH) solutions. The reaction was carried out under different conditions to obtain latices having various isoelectric points (i.e.p.). All the latices obtained were highly monodisperse and of similar particle size. Conductometric titrations of amphoteric latices revealed that both acidic and basic groups existed on their surfaces, and that the surfaces of amphoteric latices were more hydrophilic than those of P(St/AAm) latex. The adsorption of bovine serum albumin (BSA) onto the latices was also studied. The adsorption of BSA onto amphoteric latices was lower than that onto P(St/AAm) latex, and was governed by electrostatic interactions. At lower ionic strengths, the adsorption behavior of BSA onto the amphoteric (H) latex having the highest i.e.p. was different from that onto other latices, showing maximum adsorption at a higher pH than the i.e.p. of the protein.