Design of composites Na ⁺ , Mg ²⁺ , BO ₃ ³⁻ -containing calcium phosphates with ZrO ₂ : microhardness and antibacterial activity

Abstract Calcium phosphates modified with trace elements (sodium, magnesium) and borate-anions as well as composites based on them with different amount of ZrO 2 (5, 10 or 25wt%) were synthesized from aqueous solution with further heating to 600 °C. The amounts of borate-anions and sodium cations in the initial solutions influenced on crystallites size of modified calcium phosphates. Calculated lattice parameters (hexagonal system, space group Р6 3 /m ) for prepared calcium phosphates some changed comparing with corresponding data for Ca 10 (PO 4 ) 6 (OH) 2 that confirms the incorporation of doping ions in apatite-type structure. The microVickers hardness tests for Ca 9.625 Na 0.25 Mg 0.25 (PO 4 ) 5.5 (BO 3 ) 0.5 (BO 2 ) 2 and one-stage synthesized composite based on it with 25wt% of ZrO 2 showed an approximate two-fold increase in hardness from 39.2HV to 74.7HV. It was found, that the addition of 5 mM of a composite based on Ca 9.625 Na 0.25 Mg 0.25 (PO 4 ) 6 (OH) 2 with 5 wt% ZrO 2 results in an 11.3-fold and 10.9-fold inhibition of strains S. aureus and P. aeruginosa growth, respectively. The highest antibacterial activity with 100-fold decrease of S. aureus viability was found for Ca 9.625 Na 0.25 Mg 0.25 (PO 4 ) 5.5 (BO 3 ) 0.5 (BO 2 ) 2 at its adding in amount of 20 mM. Obtained results can be used for preparation of composites based on Na + , Mg 2+ , BO 3 3− -containing calcium phosphates with ZrO 2 with improved microhardness and antibacterial activity for further cytotoxicity/biocompatibility tests and evaluation of perspective of their in orthopedic application.