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Abstract: Ca ion implantation of Ti surfaces has previously been reported to enhances osseointegration in vivo. Although the mechanisms underlying the response of bone cells to these novel surfaces still remain unclear, it is possible that Ca ion-implanted Ti (Ca–Ti) may influence the growth of new bone by modulating the progression of the cell cycle. In the present study we have, therefore, examined the precise effects of Ca ion-implantation of Ti on the bone-like MG-63 cell line in vitro. The results of flow cytometry analysis showed that this surface markedly enhanced the proportion of cells which expressed Ki-67, a cell proliferation-associated nuclear antigen, compared with cells grown on the non-implanted Ti (control) surface. In addition, cultures grown on Ca–Ti and synchronized at the G1/S boundary by hydroxyurea more rapidly re-entered and progressed through the S and G2/M phases of the cell cycle than their counterparts on Ti. Ca ion-implantation also significantly increased the numbers of mitotic cells. These results thus show that alteration of the surface chemistry of Ti by high-energy implantation with Ca ion was able to substantially modulate the progression of the bone cell cycle, and suggest a possible means of enhancing the response of bone cells to implant materials. [Copyright &y& Elsevier]

Abstract: The use of calcium ion (Ca) implantation of titanium (Ti), previously reported to encourage osseointegration in vivo, has been investigated using an in vitro model in order to understand the basic mechanisms involved in the response of target cells to such surfaces. Polished Ti discs were implanted with high, medium and low (1×1017, 1×1016, 1×1015 ionscm−2) doses of Ca ions at 40keV. The effects of different levels of Ca implantation on morphology, attachment and spreading of MG-63 cells seeded on the surface of control (non-implanted) Ti and Ca–Ti discs were assessed. Further, to understand cell–material interactions at a molecular level, the expression of and integrins and the formation of vinculin-positive focal adhesion plaques were examined. In addition, the effects of pre-immersion of the Ca (high)–Ti in tissue culture medium on cell attachment were measured and correlated with specific chemical changes at the Ti surface. Our findings suggest that Ca implantation can affect the adhesion of MG-63 cells both qualitatively and quantitatively. However, this effect appears to depend on the level at which Ca ions are implanted. Results showed that although cell adhesion on Ca (high)–Ti was initially reduced, it nevertheless was not only restored but substantially increased with progressing culture times. In addition, a significantly enhanced cell spreading, formation of focal adhesion plaques and expression of integrins were measured on this particular surface. In contrast, no marked differences were observed in cell behaviour on Ca–Ti (low and medium). Pre-immersion studies indicated that the decrease in cell attachment to Ca (high)–Ti at early time periods may be linked to the presence of Ca- and P-rich particles on the surface. The absence of these particles at 24h was consistent with a significant increase in cell attachment. [Copyright &y& Elsevier]