Preparation and characterization of β-tricalcium phosphate co-doped with monovalent and divalent antibacterial metal ions

Ag+ and Zn2+ or Cu2+ ions were co-doped with beta-tricalcium phosphate (AgZn-TCP and AgCu-TCP), and their substitution models, antimicrobial activities, mechanisms and cytotoxicities were investigated. The lattice constants (a-axis and c-axis) of AgZn-TCP and AgCu-TCP decreased linearly with the amount of Zn2+ or Cu2+ ions up to 9.09 mol.%, which indicated that Ag+ ions were doped at the Ca(4) site and a vacancy in the p-TCP structure, and Zn2+ or Cu2+ ions were doped at the Ca(5) site. Antibacterial activities of AgZn-TCP and AgCu-TCP on Escherichia coli and Staphylococcus aureus were higher than those of Ag+ ions-doped beta-TCP (Ag-TCP) and pure beta-TCP. These antimicrobial activities suggested that an interaction occurred between bacteria and Ag+, Zn2+ and Cu2+ ions eluted from AgZn-TCP and AgCu-TCP and between bacteria and the free radicals generated by antibacterial agents or in bacterial cells. AgZn-TCP and AgCu-TCP can be used over long periods of time with high antimicrobial activity, because the rate at which Ag+ ions are released from AgZn-TCP and AgCu-TCP is slower than that at which Ag+ ions are released from Ag-TCP. However, it is necessary to determine the suitable amounts of Ag+, Zn2+ and Cu2+ ions in AgZn-TCP and AgCu-TCP by considering both their antimicrobial activities and cytotoxicities, because beta-TCP doped with a large amount of these metal ions exhibits cytotoxicity. Furthermore, AgZn-TCP and AgCu-TCP are considered to be promising materials for use in various fields. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.