Biphasic modified calcium phosphate: synthesis and antibacterial properties

The biphasic calcium phosphates (composite of hydroxyapatite and β-tricalcium phosphate) have significant interest due to the possibility of regulation of synthetic material bioresorption by varying ratio of its components. Biphasic calcium phosphates with different weight ratio of phases based on hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) and tricalcium phosphate (β-Ca₃(PO₄)₂) containing Na⁺ (1.1-1.2wt%), K⁺ (0.2-2.0wt%), Zn²⁺ (2.1wt%) and CO₃^2- (3.2wt%) have been prepared from aqueous solutions and heated to 500 °C. Comparison of calculated lattice parameters for both phases in obtained biphasic calcium phosphates with corresponding data for pure Ca₁₀(PO₄)₆(OH)₂ and β-Ca₃(PO₄)₂confirmed the incorporation of dopants in both phases. FTIR data indicate the partial substitution of РО₄^3-→СО₃^2-(B-type) in apatite-type calcium phosphate. It was found that modification of calcium phosphates with potassium cations and carbonate anions caused the faster partial dissolution of synthetic materials in the simulated solutions (PBS). The antibacterial activity of synthesized samples against Staphylococcus aureus, Streptococcuspyogenes and Pseudomonas aeruginosa has been evaluated. The influence of alkaline metal nature on effect of modified biphasic calcium phosphates on S. aureus and P.aeruginosa was found. The Na⁺-containing sample inhibited the growth of both S. aureus and P.aeruginosa microorganisms at adding its 20 mM while the K⁺-containing phosphate did not affect. The highest antibacterial effect against both S. aureus and P. aeruginosa was observed for Na⁺,K⁺,Zn²⁺-containing biphasic calcium phosphate. A five-fold inhibition of S. aureus cell growth was observed at adding of 10 mM of this sample, while P.aeruginosa cell growth was inhibited only at its higher amount (20 mM). It was found that all synthesized biphasic calcium phosphates didn’t effect on growth of the Streptococcus pyogenes strain.