THE INITIAL REACTIONS OF TIO2 WITH BLOOD

The natural titanium oxide (TiO2) layer of commercial sheet titanium w as dissolved in hydrofluoric acid. A new oxide layer was grown by oxid ation in nitric acid or by annealing at 700 degrees C in air. At this temperature, reaction with nitrogen is unlikely. The purity of the oxi dized sheet-titanium surfaces was investigated by Auger spectroscopy. The composition of both surfaces was TiO2 with carbon impurities. The carbon content of the acid-oxidized titanium was 20 +/- 2%, and the ca rbon content of the heat-oxidized titanium was 14 +/- 2% The initial r eactions of the TiO, surfaces with blood were investigated by short-ti me exposure to capillary blood and by detection of surface-adsorbed pl asma proteins and cells with immunofluorescence. Antibodies specific t o fibrinogen, complement factor Clq, prothrombin/thrombin, and platele t membrane antigen were used, and the fluorescence was quantitated by computer-aided image analysis. The results show that serine proteases are the dominating proteins adsorbed onto annealed titanium (Clq = 67 +/- 4.6; pt/t = 97 +/- 0.2; fib = 47 +/- 0.2). The adsorption of serin e proteases was lower and the amount of fibrinogen was higher on the a cid-oxidized surface (Clq = 46.3 +/- 2.6; pt/t = 25 +/- 2.9; fib = 64 +/- 0.7). Platelets adhered and spread on the annealed titanium surfac e within 5 sec of blood-material contact. The number of adhering plate lets was higher on the add-oxidized surface. (C) 1997 John Wiley & Son s, Inc.