COMPLEMENT ACTIVATION ON THIOL-MODIFIED GOLD SURFACES

To evaluate the importance of protein adsorption and chemical composit ion of the solid surface on complement activation, we used mercaptogly cerol (MG) and mercaptopropionic acid (MPA) modified gold surfaces as model surfaces. The complement activation by these surfaces was determ ined by measuring fluid phase iC3b and C5b-9 in serum that had been in contact with the surfaces. In addition, ''active'' C3 deposition at t he modified surfaces was measured with the use of ellipsometry, an opt ical technique. It was found that the MG surface caused pronounced pro ductions of iC3b and C5b-9 in serum as well as increased C3 deposition on the surface. In contrast, the bare gold surface and the MPA surfac e caused very little complement activation. The MG surface seems to ha ve a high affinity with immunoglobulin G (IgG) that may be one explana tion for the high complement activation ability of the MG surface. How ever, complement activation at the MG surface was relatively insensiti ve to Mg-EGTA buffer at a high serum concentration, indicating alterna tive pathway activation when classical pathway activation was inhibite d. Corresponding control experiments performed with Mg-EGTA serum at h ydrophobic silicon surfaces precoated with IgG showed no sign of alter native pathway activation. At a lower serum concentration, classical p athway activation seemed to dominate at the MG surface and the hydroph obic silicon surface precoated with IgG. Most probably, it is the hydr oxyl groups at the MG surface that are associated with alternative pat hway activation. (C) 1996 John Wiley & Sons, Inc.