A stable titanium-peroxy-radical complex is formed when metallic titanium interacts with hydrogen peroxide. The radical appears as one component in an aqueous gel formed when excess peroxides have been (catalytically) decomposed. The interaction between titanium and hydrogen peroxide may be of importance also in vivo during an inflammatory response at the implant. We report in this paper on the bactericidal effects of the titanium gel in the lacto-and myeloperoxidase-halogen systems. Escherichia coli viable count was used to evaluate the bactericidal properties of the gel and of H202 for comparison. The gel had only small or no toxic properties at high dilutions. Higher concentrations of the gel had bactericidal properties similar to those of H202. The results indicate that at physiological pH, the decomposition products of the gel are titanium hydroxide (Ti(IV)(OH-)4) and hydrogen peroxide (H202). It was found that the gel probably oxidizes glutathione directly in contrast to H202, which needs a peroxidase to do so.
A model for the interaction between titanium and hydrogen peroxide is suggested. Its consequences for the properties of titanium in vivo are also discussed.