Antibacterial activity and in vitro cytotoxicity of silver-coated coral hydroxyapatite

Abstract

Objective To evaluate the antibacterial activity against Escherichia coli and Staphylococcus aureus and cytotoxicity of silver-coated coral hydroxyapatite (Ag-CHA) at different Ag+ concentrations. Methods Vacuum freeze-drying technique was applied to obtain the silver-coated Ag-CHA at from 1 × 10-2 to 1 × 10-5 mol/L Ag+ concentrations. Antibacterial tests against Escherichia coli and Staphylococcus aureus were carried out by flat plate diffusion method. The inhibition zones were measured after culture for 24 hours to evaluate the antibacterial activity of Ag-CHA. The leaching solution of 8 × 10-5 mol/LAg-CHA was prepared and mouse fibroblast L929 was cultured at 2, 4, 7 days with the leaching solution.Finally MTT method was used to evaluate the cytotoxicity of Ag-CHA. Results Ag-CHA at a concentration from 1 × 10-2 to 8 × 10 -5 mol/L Ag+ had obvious inhibition zones of over 12 mm against E. coli and S. aureus, whereas Ag-CHA at a concentration less than 8 × 10-5 mol/L had no antibacterial effect. Ag-CHA from 0 to 8 × 10-5 mol/L Ag+ had no cytotoxicity on L929. Cell relative growth rates(RGR) for 8 × 10 -5mol/L Ag-CHA were all larger than 90% and the cytotoxicity grades were 0 or 1 after culture for 2, 4, 7days. Conclusion Ag-CHA at a concentration of 8 × 10-5 mol/L Ag+ may have the most effective antibacterial activity but no cytotoxicity. Key words: Hydroxyapatites; Microbial sensitivity tests; Cytotoxicity tests, immunologic; Staphylococcus, aureus; Escherichiacoli