PROTEIN ADSORPTION ON LOW-TEMPERATURE ISOTROPIC CARBON .2. EFFECTS OF SURFACE-CHARGE OF SOLIDS

Protein adsorption on low-temperature isotropic carbon (LTIC) and on gold electrodes was studied via changes in their double-layer capacitance. The surface charge of the electrodes was controlled by a DC potential. The more negatively charged LTIC always adsorbed more proteins from near neutral or acidic solutions, regardless of the charge on the proteins. Adsorption patterns did not change when the solution ionic strength was varied. At pH 7.4 the more negatively charged gold adsorbed the more positively charged proteins. Kinetic data indicate that higher adsorbed amounts were accompanied by higher initial adsorption rates. The electrostatic interaction did not appear to play a significant role in the interactions between the proteins and LTIC. Our hypothesis suggests hydrophobic and interfacial water properties are involved in protein adsorption on LTIC. (C) 1994 Academic Press, Inc.