Titanium with different oxides: in vitro studies of protein adsorption and contact activation.

Adsorption of albumin (HSA) and fibrinogen (Fib) from human blood plasma onto titanium surfaces with varying oxide properties was studied with an enzyme-linked immunosorbent assay. The intrinsic activation of blood coagulation (contact activation) was studied in vitro using a kallikrein-sensitive substrate. The sample surfaces were characterized with Fourier transform Raman spectroscopy. Auger electron spectroscopy and atomic force microscopy. Low Fib and high HSA adsorption was observed for all titanium samples except for the radio frequency plasma-treated and water-incubated samples, which adsorbed significantly lower amounts of both. Oxide thickness and carbon contamination showed no influence on protein adsorption or contact activation. Smooth samples with a surface roughness (Rrms) < 1 nm showed some correlation between surface wettability and adsorption of Fib and HSA, whereas rough surfaces (Rrms > 5 nm) did not. To varying degrees, all titanium surfaces indicated activation of the intrinsic pathway of coagulation as determined by their kallikrein formation in plasma.