AGGREGATION OF HSA, IGG, AND FIBRINOGEN ON METHYLATED SILICON SURFACES

Ellipsometry was used to quantify adsorption and tapping mode atomic f orce microscopy to study surface aggregation of human serum albumin (H SA), immunoglobulin G (Igc), and fibrinogen (Fib) adsorbed from aqueou s solutions onto methylated silicon surfaces. After exposure to air th e protein monolayers were spontaneously restructured, exposing disorga nized areas with heterogeneity depending on the degree of surface meth ylation. The aggregation patterns also depended on some properties of the adsorbed protein (such as the number of contact points with the su rface), but seemed to be almost independent of the adsorption time. Th e results indicate that aggregates were formed due to lateral reorgani zation on the adsorbed layer at the air-liquid interface during the dr ying process. The interpretation is that the heterogeneous structures result from a thermodynamically driven interaction between the hydroph obic surface and the similarly hydrophobic air. The main conclusion th at can be extracted from this work is that fibrinogen (hydrophobic and large protein) interacts more irreversibly with the silicon surfaces than IgG, and much more so than HSA, which is less hydrophobic and sma ller than fibrinogen. (C) 1998 Academic Press.