Characterization of protein adsorption on membrane surface by enzyme linked immunoassay

A new method for determining the amount of adsorbed protein on membrane sur face is developed on the basis of immunoassay using alkaline phosphotase as enzyme label and 4-nitrophenyl phosphate as substrate. Adsorption of human serum albumin (HSA) on HT Tuffryn, a kind of polysulfone microfiltration m embrane, in the absence and presence of an electric field is investigated e xperimentally. It is shown that the adsorption of HSA on HT membrane surfac e is finished within 5 min and the amount of the adsorbed HSA decreases wit h the increase in pH but is not sensitive to salt concentration. Desorption of the adsorbed HSA from HT membrane surface can only be achieved with NaO H. Adding surfactants in HSA solution to prevent the adsorption is attempte d and Tween 20 shows the best shielding function compared to polyethylene g lycol 6000 and pluronic-F108. A critical concentration exists for Tween 20, below which the increase in the concentration of Tween 20 results in a cor responding reduction of adsorbed HSA. Introducing electric field into the a dsorption leads to an enhanced adsorption of HSA, which appears to be a fun ction of pH and the electric held strength. (C) 2000 Elsevier Science B.V. All rights reserved.