Mg²⁺, Sr²⁺, Ag⁺, and Cu²⁺ co-doped -tricalcium phosphate: Improved thermal stability and mechanical and biological properties

beta-tricalcium phosphate (beta-TCP, beta-Ca-3(PO4)(2)) is an attractive biomaterial for bone repair applications. However, its sintering and mechanical properties are limited by a problematic phase transition to a-TCP. Cationic doping of beta-TCP is able to postpone the formation of a-TCP allowing higher sintering temperatures and better mechanical properties. The co-doping of beta-TCP with Mg2+ and S-r2+ has already been studied in detail, but the addition of antibacterial cations (Ag+ and Cu2+) on the Mg-Sr beta-TCP co-doped composition remains unexplored. Thus, two co-doped beta-TCP compositions were realized by aqueous precipitation technique without any secondary phase and compared with undoped beta-TCP: Mg-Sr (2.0-2.0 mol%) and Mg-Sr-Ag-Cu (2.0-2.0-0.1-0.1 mol%). Differential thermal analysis and dilatometry analyses showed a slight decrease of the beta-TCP. aTCP phase transition temperature for the Mg-Sr-Ag- Cu (2.0-2.0-0.1-0.1% mol) composition as compared to the Mg-Sr (2.0-2.0 mol%). However, both exhibited much higher transition temperatures than undoped beta-TCP. The addition of Ag+ and Cu2+ slightly reduces the grain size after sintering compared to the Mg-Sr (2.0-2.0 mol%) and the undoped compositions. The co-doped compositions also exhibited improved mechanical properties, specifically a higher Vickers hardness and elastic modulus. Finally, cell proliferation assays showed that the presence of dopants, even Ag+ and Cu2+, does not affect the survival and proliferation of cells. Thus, the use ofMg(2+), Sr2+, Ag+, andCu(2+) co-doped beta-TCP could be very promising for biomedical applications due to the improvements of these dopants on the thermal stability and mechanical and biological properties.