Biocompatibility and photoinactivation evaluation of zinc hydroxide chloride nanosheets against Streptococcus mutans

Abstract

Background: Considering the efficacy of antimicrobial photodynamic therapy (PDT) in inactivating bacteria, this study reports that zinc hydroxide chloride nanosheets (ZHC-NSs) are useful for this purpose. Materials & methods: The characterization of ZHC-NSs was performed using microscopic and spectroscopic techniques. The irritation test, acute toxicity test, and genotoxicity test of ZHC-NSs were evaluated and their effects on human pulp fibroblast cells (HPFC) viability, intracellular reactive oxygen species (ROS) levels, and antibacterial activity of ZHC-NSs (1–8 mg ml−1) alone or in light conditions were investigated. Results: The ZHC-NSs structure showed a crystalline form and their sheets’ thickness had an average size of 129.6 ± 19.50 nm. ZHC-NSs did not severely damage internal organs and were not genotoxic. The cytotoxic effect of ZHC-NSs on HPFC was concentration-dependent so that ZHC-NSs at higher concentrations (4 and 8 mg ml−1) killed half of the HPFC cells. When ZHC-NSs were used in combination with a 980 nm diode laser, namely ZHC-NS©, ROS production increased and led to enhanced antibacterial activity against Streptococcus mutans in planktonic and biofilm form. A statistically significant difference was found between ZHC-NSs without laser irradiation and photoexcited ZHC-NSs. Conclusion: ZHC-NSs© with the potential ability to produce ROS could be effective in complementary treatment against S. mutans.