Antibacterial Copper-Doped Calcium Phosphate Glasses for Bone Tissue Regeneration

Abstract

Calcium phosphate glasses are a promising new generation of biomaterials that can simultaneously induce tissue regeneration and controlled release of therapeutic molecules. In this work, novel calcium phosphate glasses containing 0, 2, 4, and 6 mol % Cu²⁺ were synthesized via room temperature precipitation reaction in aqueous solution. The effect of Cu²⁺ addition on the glass properties and structure was investigated using thermal analysis, ³¹P solid-state MAS NMR, Raman spectroscopy, and X-ray diffraction. All glasses crystallize at temperature >500 °C and are mainly formed by Q¹ groups. The release of P, Ca, and Cu in solution over time was monitored via inductively coupled plasma-optical emission spectroscopy. It was found that with increasing Cu content, the amount of P and Ca released decreases whereas the amount of Cu released increases. The effect of Cu²⁺ release on the antibacterial activity against S. aureus, a bacterial strain commonly found in postsurgery infections, has been investigated. The addition of copper has been shown to infer the glasses antibacterial properties. As expected, the antibacterial activity of the glasses increases with increasing Cu²⁺ content. Cytocompatibility was assessed by seeding human osteoblast-like osteosarcoma cells Saos-2 (HTB85) on the glass particles. A significant increase in cell number was observed in all the glasses investigated. The copper-doped calcium phosphate glasses have proven to be multifunctional, as they combine bone regenerative properties with antibacterial activity. Therefore, they have great potential as antibacterial bioresorbable materials for hard tissue regeneration.

Keywords: antibacterial activity; bone regeneration; calcium phosphate glasses; controlled ion release.