Synthesis and characterization of a novel silver-substituted calcium phosphate cement

Antibacterial materials play an important role in clinical application, and silver has been known to exhibit strong cytotoxicity towards a broad range of micro-organisms. In this work, the amorphous calcium phosphate with silver substitution (Ag-ACP) was synthesized by chemical precipitation method, and the valence of silver in ACP was adjusted by temperature. The processed Ag-ACP was combined with slightly acidic compounds to form new calcium phosphate cement (CPC). Our results indicate that the valence of silver in CPC was adjusted successfully by chemical precipitation method and heat treatment. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results demonstrated that silver ion in CPC-1 and CPC-2 existed in Ag3PO4; after heat treatment of 460°C, silver became more stable in CPC-3 and CPC-4. Silver in CPC-1 and CPC-2 exhibited better releasing property. After heat treatment at 460°C, the amount of silver ion released from CPC decreased significantly. Besides, the antibacterial ability of Ag-CPC was adjusted by changing the valence of silver in Ag-CPC. Depending on the low valence of silver and good silver release, CPC-1 and CPC-2 exhibited better antibacterial activity. We believe that this study will motivate the development and applications of antibacterial CPC in bone tissue regeneration.