Novel electrochemical patterning of titanium alloy to control osteogenesis at the bone-implant interface

Abstract

The aims of this thesis were to fully characterise the surface properties of titanium alloy treated with a novel process of electrochemical etching and to assess the effect of these surfaces on osseointegration and the behaviour of osteoblasts. In vitro investigation was performed using rat osteoblasts and human mesenchymal cells. Significant differences were observed in cell polarity and cell area between cells cultured on 3V and 5V and those treated at 9V. Significantly greater mean focal adhesion area and mean number of focal adhesions per unit cell area were also observed between the 3V and 5V treated surfaces compared to the 9V treated surfaces. Longer term experiments revealed no significant changes in the levels of alkaline phosphatase activity between cells cultured on the different surfaces. After 28 days in culture, cells were stained for mineralised deposits and no significant differences were seen in the total area of bone nodules found on the experimental surfaces. To assess the influence of the treated surfaces on bone cell biology, immunofluorescence was used to localise cadherin-11 and activity and inhibition assays were performed for small GTPases of the Rho family. On the 9V treated surfaces, significantly increased staining for cadherin-11 was seen, as well as significantly greater RhoA activity. In vivo experiments were performed with electrochemically treated titanium implants in a rat tibia model. Analysis of micro-CT images of retrieved tibias revealed a significantly greater area of mineralised bone matrix in contact with the implant surface for the 9V treated surfaces and the same trend was observed on histomorphometric analysis. High variability in the mechanical testing data meant that no significant differences were seen, but a trend for greater load to failure of the bone-implant interface was observed for the 3V treated surfaces.