A release of Ti-ions from four distinct surface oxides into a liquid Dulbecco Modified Eagle Medium is investigated. Four oxide layers grown on bulk titanium samples were characterized in detail with respect to their morphology, wetting parameters and phase and chemical compositions and subsequently exposed to the medium. In spite of fundamental differences, which existed between the four individual layers in terms of their thickness, nanoscale structure and contact area with the liquid, a concentration of Ti-ions transferred into the medium was markedly similar. These results suggest that a key thermodynamic parameter governing the transfer of Ti-ions is their solubility limit in the medium. For the investigated oxide-liquid systems, the solubility limit was estimated as 10-20 mu g/l at 37 degrees C. Interestingly, many less systematic data reported so far in the literature can be rationalized based on a similar saturation scenario.