Structural and Biological Enhancement of Cu-Incorporated Biphasic Calcium Phosphate Synthesized via a Sol–Gel Combustion Method

Abstract

Biphasic Calcium Phosphate (BCP) is a critical bioceramic for bone regeneration due to its biocompatibility and osteoconductivity. This study investigates the enhancement of BCP through the incorporation of copper (Cu) ions using a sol–gel combustion method at concentrations of 0, 1, 3, and 5 mol%. XRD analysis revealed that while hydroxyapatite (HAp) remained the primary phase, Cu incorporation promoted the formation of secondary β-Tricalcium Phosphate (β-TCP) and Calcium Oxide (CaO) phases. XANES spectra confirmed that Cu exists in a +2 oxidation state and forms a separate CuO phase rather than substituting for Ca sites. Bioactivity assessments via 7-day immersion in Simulated Body Fluid (SBF) demonstrated that the 5Cu–BCP sample most effectively promoted the formation of a bone-like apatite layer with a Ca/P ratio of 1.63. Antibacterial tests showed that Cu-doped samples inhibited S. aureus growth, but only 5Cu–BCP was effective against the Gram-negative P. aeruginosa. Furthermore, while the 1Cu–BCP sample showed significant cytotoxicity, higher Cu concentrations (3Cu and 5Cu) exhibited better cell viability, likely due to more effective structural incorporation of CuO. These findings suggest that 5Cu–BCP is a promising material for biomedical applications, offering a superior balance of bioactivity, antibacterial performance, and biocompatibility.