Abstract: The elucidation of key influence factors for electrostatic adsorption is very important to control protein nonspecific adsorption on modified surfaces. In this study, real-time surface plasmon resonance technique is used to characterize the electrostatic adsorption of two proteins (mouse IgGand protein A) on carboxymethyldextran-modified surface. The results show that protein solution pHand ionic strength are key influence factors for efficient electrostatic adsorption. The influence of protein solution pHon the amount of electrostatic adsorption depends on the type of the charge and the charge density of both protein and modified matrix on the surface. The electrostatic adsorption process involves a competition between the positively charged protein and other positively charged species in the buffer solution. Adecrease of ionic strength leads to an increasing electrostatic adsorption. The kinetic adsorption constants of protein Aat different pHvalues were also calculated and compared.

Key words: Surface plasmon resonance, Electrostatic adsorption, Protein