Osteogenic, Angiogenic, and Antibacterial Bioactive Nano-Hydroxyapatite Co-Synthesized Using γ-Polyglutamic Acid and Copper.

Nano-antibacterial calcium phosphate (CaP) has attracted intense attention with regard to its wide variety of medical and biological applications. The γ-polyglutamic acid and copper cosynthesized hydroxyapatite (γ-PGA/CuxHAp) was synthesized using the wet method. Structural and chemical characterizations demonstrate that copper was quantitatively incorporated into the hydroxyapatite structure, and the degree of Cu substitution was up to 20 mol % in the synthesized nanocrystals. Morphology characterization showed that the size of the γ-PGA/CuxHAp nanoparticles decreases with the increased copper content. γ-PGA/CuxHAp exhibited a steady release of Cu ions. Two experimental protocols were applied to compare the antibacterial activity of the γ-PGA/CuxHAp samples. A positive correlation was observed between Cu content and the inhibition of bacterial growth. The study also showed that nanoparticles with smaller particle sizes exhibited higher antibacterial activities than the larger particles. Endothelial and osteoblast cells rapidly proliferated on γ-PGA/CuxHAp, whereas high concentrations (20 mol %) of Cu ions reduced cell proliferation. In the rat calvarial defect model, some γ-PGA/CuxHAp samples such as γ-PGA/CuxHAp (x = 8, 16) showed efficient bone regeneration capacities at 12 weeks post implantation. Thus, the multibiofunctional γ-PGA/CuxHAp nanocomposite exhibited degradative, angiogenic, bactericidal and bone regenerative properties, providing a potential means to address some of the critical challenges in the field of bone tissue engineering.