Changes in surface composition of the Ti-6Al-4V implant alloy by cultured macrophage cells

In this study, X-ray photoelectron spectroscopy (XPS) was used to evaluate the hypothesis that macrophage cells and their released compounds change Ti-6Al-4V surface oxide composition. Ti-6Al-4V surfaces, prepared to simulate clinical conditions, were exposed for 3 days to cell culture medium, macrophage cells, or macrophage cells activated to release inflammatory reactive chemical species (RCS). The as-polished samples were used as controls. The as-polished samples exhibited typical TiO2 surface oxides. After samples were exposed to medium, only C, O and N peaks from absorbed proteins were observed. When cultured with cells or activated cells, the Ti peaks reappeared and there was a significant shift in the O 1s peak to lower metal oxide binding energies (similar to530 eV). This shift was associated with a significant increase in total metal oxides on sample surfaces as compared to medium only surfaces. With activated cells, the enhancement of the surface oxides was attributed to oxidation of the surface by the RCS released by activated macrophage cells (e.g. O-2 + NO --> NO3- and M + NO3- --> M=O + NO2-). These data support the hypothesis that macrophage cells and released RCS affect Ti-6Al-4V surface oxides. Changes in surface oxides are important since they may affect alloy-tissue interactions. (C) 2003 Elsevier B.V. All rights reserved.