EXPERIMENTAL APPROACH TO A BIOLOGICAL CHARACTERIZATION OF MATERIALS

Titanium oxide surfaces with thin (4 to 5 nm) or thick (30-40 nm) TiO2 layers and rough (R-rms 1.9 mu m) or smooth (R-rms 0.45 mu m) surface structure were exposed to capillary blood for 5 s through 64 min. The adsorption of main plasma proteins (albumin, IgG, fibrinogen), bindin g of cascade enzymes (serine proteases) and adhesion and activation of blood cells was measured with immunofluorescence techniques using spe cific antibodies, the binding of which was quantitated by computer-aid ed image analysis. The activation of cascade enzymes was detected with antibodies against prothrombin/thrombin (terminal step in the coagula tion cascade), C1q and C3c (initial complement activation), terminal c omplement complex (TCC), and plasmin (terminal step in fibrinolysis). The activation of cells was measured by expression of selectin (platel et CD62), expression of integrins (neutrophil CD11b), or respiratory b urst (NBT test) of peritoneal leucocytes adhering to the surfaces afte r in vivo exposure. The results show different profiles of protein ads orption at the four surfaces. Fibrinogen was the dominating protein on all surfaces, significant amounts of IgG was found on the rough surfa ces only. Prothrombin/thrombin and C1q were found initially on the thi ck-rough surface only. No TCC or plasmin levels were detected during t he exposure time studied. Platelets and neutrophils were activated to a significantly higher degree on rough surfaces than on smooth, and ne utrophils more on the rough surface with a thin oxide layer than on th e thick one. The ensemble of antigens and enzyme activity detected sho ws a fingerprint which is unique for each material investigated. (C) 1 997 American Vacuum Society.