Effect of zinc oxide addition on antimicrobial and antibiofilm activity of hydroxyapatite: a potential nanocomposite for biomedical applications

Bacterial infections and biofilm formations are the main problems associated with implants. Hence, the aims of this study are to develop nanocomposite biomaterials having different ratios of hydroxyapatite nanoparticles (nHAP) with green and chemically synthesized zinc oxide (ZnO) nanoparticle (NP) and examine its antimicrobial and antibiofilm activity. The synthesized nanoparticles were characterized for phase and microstructural analysis. The nanocomposite at 90:10, 75:25 and 60:40 ratio of nHAP and ZnO NPs respectively, showed a different level of antimicrobial and antibiofilm activity against clinical specimen isolated gram-positive Staphylococcus aureus and gram-negative Escherichia coli. Moreover, the minimum inhibitory concentration (MIC) was the lowest concentration of ZnO NPs in the nanocomposite inhibiting the growth of each bacteria species and it was investigated for the given ratio of nanoparticles and found to be 0.2 mg/mL of 90:10 nanocomposite for both pathogens. The minimum bactericidal concentration (MBC) was the lowest concentration of ZnO NPs in the nanocomposite required to kill each of the bacterial species and it was found to be 0.2 mg/mL of 75:25 and 60:40 nanocomposite for S. aureus and E. coli, respectively. The maximum percentage of biofilm inhibition was found at 60 (nHAP): 40 (ZnO NPs) ratio of the nanocomposites. It was 52% and 54% against S. aureus and E. coli biofilm respectively, for green synthesized ZnO NPs and 51% and 52% against S. aureus and E. coli biofilm respectively, for chemically synthesized ZnO NPs. Hence, based on these results we suggest that the biomaterials containing different ratios of nHAP- ZnO NPs can be used as antimicrobial and antibiofilm materials in bone implant and bone regenerative medicine.