BLOOD PROTEIN INTERACTIONS WITH CHROMIUM SURFACES

Protein adsorption, contact activation, and complement activation were studied on thin evaporated films of chromium (Cr) in vitro. The surfa ces were, prior to the experiments, cleaned in either ethanol and wate r, or in a basic peroxide solution (RCA standard clean 1, SC-1). Surfa ce spectroscopic studies of the outermost oxides showed a significant reduction of carbon contaminants after washing in SC-1 bur also sugges ted an increase in the oxidation state as compared with the ethanol-wa shed surfaces. In situ ellipsometry combined with antibody techniques was used to determine protein deposition and antibody binding onto sur faces after incubations in heparin plasma or in normal serum. Incubati on times from 1 to 10 min in serum showed increased depositions of ser um and antibodies to complement factor 3c (C3c) and was larger on etha nol-washed surfaces than on surfaces washed in SC-1. ELISA methods ind icated increased amounts of iC3b in serum for both surfaces, but no pr esence of C3 convertases (C4d or Bb fractions). A low or transient com plement activation via the classical pathway was indicated on ethanol washed Cr, since deposition of secondary antibodies to complement fact or 1q (C1q) was observed only after short incubation times in serum. N o procoagulant activity of Cr was indicated, since only low amounts of antibodies to factor XII (F XII), prekallikrein (PKK), and high molec ular weight kiniogen (HMWK) bound to the surfaces after incubations in heparin plasma. These results were confirmed using a colorimetric ass ay where the relative amounts of free plasma kallikrein was assessed u sing a chromogenic substrate, H-D-Pro-Phe-Arg-pNA (S-2302).