Fabrication of silver-doped apatite powders from silver-substituted octacalcium phosphate powders via solid-solid phase-conversion process

The excellent biocompatibility of apatite (hydroxyapatite, HAp; carbonate apatite, CO3Ap) materials makes them suitable candidates as bone substitutes. However, they have no antibacterial ability. Meanwhile, silver (Ag) exhibits excellent antibacterial properties across a wide antibacterial spectrum. However, soluble Ag salts exhibit cytotoxicity and poor aesthetic properties. We dope Ag into an apatite unit lattice in order for the composite material to exhibit antibacterial contact abilities while simultaneously limiting the release of Ag+, which is the primary cause of the unwanted color changes and cytotoxicity. When a crystal structure in which silver ions are substituted for Ca in octacalcium phosphate (OCP) (Ag-OCP) is immersed in water and/or (NH4)2CO3-containing solutions, Ag-OCP is converted into an apatite containing Ag via a solid-solid phase-transformation process. The Ag contents of the apatite and precursor Ag-OCP are the same. The CO3 content of apatite samples depends on the (NH4)2CO3 concentration of the treated solutions. A single-pot, single-step treatment enables the synthesis of both Ag-containing HAp and CO3Ap. Further, these Ag-containing HAp and CO3Ap samples show little color change from that of the precursor Ag-OCP.

Automated summary

Apatite materials with excellent biocompatibility are suitable bone substitutes, while silver exhibits strong antibacterial properties. By doping silver into the apatite lattice, the composite material can have antibacterial abilities without releasing toxic Ag+ ions. The presence of silver in apatite can be achieved through a solid-solid phase transformation process, maintaining the color and reducing cytotoxicity.