AGGREGATION OF IGG ON METHYLATED SILICON SURFACES STUDIED BY TAPPING MODE ATOMIC-FORCE MICROSCOPY

Tapping mode atomic force microscopy was used to study aggregation pat terns of human immunoglobulin G (IgG) adsorbed from aqueous solutions onto silicon surfaces methylated in dichlorodimethylsilane. Formation of dendrite-like aggregates of IgG were observed after air exposure an d appeared to be highly dependent on surface methylation as well as on protein concentration. Crosslinking the protein layer in 0.5% glutara ldehyde prior to air exposure resulted in homogeneous protein distribu tions with significantly reduced aggregation. This, and experiments us ing lyophilization techniques, indicates that aggregates form due to a lateral reorganization of the adsorbed protein layer at the air-liqui d interface. (C) 1995 Academic Press,Inc.