Noncytotoxic zinc-doped nanohydroxyapatite-based bone scaffolds with strong bactericidal, bacteriostatic, and antibiofilm activity.

Abstract

Development of bone scaffolds that are nontoxic to eukaryotic cells, while revealing bactericidal activity still remains a huge challenge for the scientific community. It should be noted that only bacteriostatic (the ability of the biomaterial to inhibit the growth of bacteria) and bactericidal (the ability to kill >99.9% bacteria) activities have clinical importance. Unfortunately, many material scientists are confused with the microbiological definition of antibacterial action and consider biomaterials causing reduction in colony-forming units (CFUs) by 50-80% as promising antibacterial implants. The aim of this study was to synthesize three variants of Zn-doped hydroxyapatite (HA) nanopowder, which were characterized by different content of Zn2+ and served as a powder phase for the production of novel macroporous chitosan/agarose/nanoHA biomaterials with high antibacterial activity. Within this study, it was proven that the scaffold with a low zinc content (doping level 0.03mol for 1mol of HA; 0.2wt%) revealed the gradual and slow release of the Zn2+ ions, preventing against accumulation of high and toxic concentration of therapeutic agents and providing prolonged antibacterial activity. Moreover, developed biomaterial was nontoxic to human osteoblasts and showed anti-biofilm properties, bactericidal activity (> 99.9% of bacteria killed) against Staphylococcus epidermidis and Escherichia coli, significant antibacterial activity against Staphylococcus aureus (98.5% of bacteria killed), and also bacteriostatic activity against Pseudomonas aeruginosa. Thus, the developed Zn-doped HA-based bone scaffold has excellent antibacterial properties without toxicity against eukaryotic cells, being a promising biomaterial for biomedical applications to repair bone defects and prevent post-surgery infections.