Antibacterial activity and mechanism of Ag/ZnO nanocomposite against anaerobic oral pathogen Streptococcus mutans.

Dental caries is a widespread disease mainly caused by the anaerobic oral pathogen Streptococcus mutans (S. mutans). Ag/ZnO nanocomposite is an efficient antibacterial agent because of its high antibacterial activity and low cytotoxicity. In this study, rod-like Ag/ZnO nanocomposite was synthesized through a deposition-precipitation method and characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The activity of Ag/ZnO nanocomposite against S. mutans was evaluated by determining the minimal inhibitory concentration, minimum bactericidal concentration and growth inhibition curve. The results showed that Ag/ZnO nanocomposite displayed higher activity against S. mutans compared with pure ZnO nanorods. Moreover, the antibacterial mechanism was investigated by determining the bacterial membrane potential, release of K, intracellular reactive oxygen generation and lipid peroxidation. Disruption of membrane function and oxidation of biomacromolecules played important role in the antibacterial action of Ag/ZnO nanocomposite. This work proposes a potentially effective dental antibacterial agent against the dental caries-causing S. mutans.