Interactions between human whole blood and modified TiO2-surfaces: Influence of surface topography and oxide thickness on leukocyte adhesion and activation

An in vitro model (Nygren et al., J Lab Clin Med 129 (1997) 35-46) was used to investigate interactions between leukocytes and four modified TiO2-surf aces. Surface topography was measured using scanning electron microscopy an d optical profilometry while Auger electron spectroscopy was used to determ ine surface composition and oxide thickness. The surfaces were either smoot h or rough with either thin or thick oxides. All surfaces consisted of TiO2 covered by a carbonaceous layer. The surfaces were incubated with capillar y blood for time periods of between 8 min and 32h. Immunofluorescence techn iques together with computer aided image analysis and chemiluminescence tec hnique were used to detect cell adhesion, expression of adhesion receptors and the zymosan-stimulated respiratory burst response. Leukocyte adhesion t o the surfaces increased during the first hours of blood-material contact a nd then decreased. Polymorphonuclear granulocytes were the dominating leuko cytes on all surfaces followed by monocytes. Cells adhering to rough surfac es had higher normalized expression of adhesive receptors than cells on smo oth surfaces. Maximum respiratory burst response occurred earlier on the sm ooth than on the rough surfaces. In conclusion, topography had a greater im pact than oxide thickness on most cellular reactions investigated, but the latter often had a dampening effect on the responses. (C) 2001 Elsevier Sci ence Ltd. All rights reserved.