Cymbopogon citratus essential oil infused zinc oxide nanoparticles for eco-friendly anticariogenic action.

OBJECTIVE

Dental caries is a prevalent oral health problem primarily driven by Streptococcus mutans. This study focused on the green synthesis of zinc oxide nanoparticles incorporated with Cymbopogon citratus essential oil (CEOZnONPs) and evaluated their anti-cariogenic efficacy against S. mutans.

METHODOLOGY: CEOZnONPs were prepared by dropwise addition of essential oil into zinc acetate solution at 100 °C, pH 7, and 800 rpm with polysorbate 80 as emulsifier. The nanoparticles were characterized by UV-Vis spectroscopy, HR-TEM, zeta potential, XRD, and FTIR. Antibacterial activity was assessed using MIC/MBC, adherence, biofilm inhibition, EPS production, and acidogenesis assays. An in vivo Wistar rat caries model and cytotoxicity assay on HeLa cell lines further validated efficacy and safety.

RESULTS

Morphological analysis revealed that CEOZnONPs were predominantly spherical and rod-shaped with an average particle size of 49 nm. Its antibacterial activity demonstrated a MIC of 5 µg/mL and MBC of 10 µg/mL, inhibiting adherence to tooth surfaces (85%-97%), biofilm formation, and EPS production. The antioxidant activity showed DPPH and ABTS radical scavenging of 65.28% and 75.24%, respectively. Acid production by S. mutans was significantly reduced following treatment, with pH shifting from 4.5 to 6.2. These findings were corroborated by an in vivo study, which showed a substantial reduction in S. mutans colonies in Wistar rats over five weeks. Furthermore, the CEOZnONPs (90 µg/mL) were also non-cytotoxic to HeLa cell lines.

CONCLUSION

This study is the first to report the antibacterial and anti-cariogenic efficacy of CEOZnONPs, which introduces a significant therapeutic approach. It is environmentally friendly and highly effective in combating S. mutans and preventing dental caries, opening novel avenues for future oral treatments.

CLINICAL RELEVANCE: This nano-herbal formulation offers a promising, biocompatible alternative to conventional antimicrobials, with the potential to revolutionize caries prevention strategies in clinical dentistry.