Control of gene transfer on a DNA-fibronectin-apatite composite layer by the incorporation of carbonate and fluoride ions.

Gene transfer techniques are useful tools for controlling cell behavior, such as proliferation and differentiation. We have recently developed an efficient area-specific gene transfer system using a DNA-fibronectin-apatite composite layer (DF-Ap layer). In this system, partial dissolution of the composite layer is likely to be a crucial step for gene transfer. In the present study, layer solubility was adjusted by incorporating various contents of carbonate or fluoride ions into the DF-Ap layer via ionic substitution for the apatite crystals. Carbonate ion incorporation increased the solubility of the DF-Ap layer, thereby increasing the efficiency of gene transfer on the layer. In contrast, the incorporation of fluoride ions decreased the solubility of the DF-Ap layer, thereby decreasing the efficiency and delaying the timing of gene transfer on the layer dose-dependently. The present gene transfer system with controllable efficiency and timing would be useful in tissue engineering applications because cell differentiation can be induced effectively by regulating appropriate gene expression with suitable timing.