In vitro plasma protein adsorption and kallikrein formation on 3-mercaptopropionic acid, L-cysteine and glutathione immobilized onto gold.

3-Mercaptopropionic acid (MPA), L-cysteine (L-cys), and glutathione (GSH) monolayers were immobilized onto gold and used in in vitro protein tests. The surfaces were characterized with ellipsometry, static contact angle measurements, atomic force microscopy, and Fourier transform infrared reflection absorption spectroscopy (FT-IRAS). After incubations in human plasma and antibody solutions, the surface antisera binding patterns were determined with ellipsometry. Using serum instead of plasma, complement activation was studied in the same fashion. Activated coagulation Factor XII and kallikrein formation on the surfaces and in the plasma were studied using a kallikrein-specific colorimetric assay. 3-Mercaptopropionic acid indicated contact activation of coagulation but L-cysteine did not. Glutathione displayed low deposition of plasma proteins, large deposition of proteins from serum, and did not promote kallikrein formation. None of the surfaces could be attributed complement activating properties, as determined by antibody deposition. The present study demonstrates that surface biology in complex model systems can be conveniently studied in vitro through systematic and well defined surface modifications.