Biocompatibility of Silver-Containing Calcium-Phosphate Cements with Anti-Bacterial Properties

Abstract

We have previously synthesized silver-containing hydroxyapatite (Ag-HAp) powders by an ultrasonic spray-pyrolysis (USSP) technique. On the other hand, we have successfully fabricated novel calcium-phosphate cements (CPCs) composed of mainly β-tricalcium phosphate (β-TCP) phase with anti-washout property (hereafter, β-TCP cement), which was set on the basis of chelate-bonding ability of inositol phosphate (IP6). In this study, we developed novel CPCs with both anti-bacterial and anti-washout properties by adding the Ag-HAp powder into the above β-TCP cements, and examined their anti-bacterial property and cytotoxicity. The Ag-HAp powders with Ag contents of 0, 2, and 5 mol% as a nominal composition were synthesized by an USSP technique. The raw powder for β-TCP cement was prepared by ball-milling the commercially-available β-TCP powder in the IP6 solution. The Ag-HAp/β-TCP powders were prepared by mixing Ag-HAp powder and β-TCP cement powder at a ratio of 25:75 in mass. The Ag-HAp/β-TCP cement was fabricated by mixing the above-mentioned Ag-HAp/β-TCP powder and 2.5 mass% Na2HPO4 solution at a powder/liquid ratio of 1/0.3 [g/cm3]. The anti-bacterial property of resulting cements was evaluated using Staphylococcus aureus by biofilm formation test. The Ag-HAp/β-TCP cements containing 2 and 5 mol% Ag showed strong anti-bacterial property among examined specimens. Furthermore, the cytotoxicity of Ag+ ion eluted from these cements was also examined using osteoblastic MC3T3-E1 cells and Transwell® kit. The relative cell viability cultured on each Ag-containing cement specimen was over 80 %, compared with the control (polystyrene plate). These results demonstrate that the present Ag-HAp/β-TCP cements containing 2 mol% Ag are promising one of the candidates as CPCs with both anti-bacterial property and biocompatibility.