Mentha spicata-mediated silver nanoparticles for combating Streptococcus mutans and oral cancer cells

A sustainable and ecologically safe substitute for traditional chemical synthesis, eco-friendly synthsis of silver nanoparticles (Ag-NPs) using plant-based extract offers promising biological opportunities. In this study, Ag-NPs were rapidly synthesized from an aqueous extract of Mentha spicata leaves and analyzed using a variety of techniques, including atomic force microscopy (AFM), transmission electron microscopy (TEM), zeta potential measurement, X-ray diffraction (XRD), UV-vis spectroscopy, and Fourier transform infrared spectroscopy (FTIR). Having a negative surface charge (- 32.5 mV) and an average width of 33 nm, the resultant nanoparticles were primarily spherical, indicating their colloidal stability. Streptococcus mutans ATCC 25175 was significantly inhibited by the antimicrobial evaluation, which revealed a minimum inhibitory concentration (MIC) of 0.125 mg/mL and a distinct inhibition zone of 20 mm. Planktonic growth was unaffected, however biofilm formation decreased by 77.3% (p < 0.05) at sub-MIC values (0.031 mg/mL). Computational docking further indicated potential interactions of Ag-NPs with dihydroorotase synthase and quorum sensing regulatory proteins, suggesting a mechanistic role in disrupting biofilm development. The nanoparticles also showed a high level of cytotoxicity against OECM-1 oral cancer cells, with an IC₅₀ of 24.21 µg/mL and an inhibition of up to 91.6% at 62.5 µg/mL. Collectively, these outcomes underscore the dual antimicrobial and anticancer properties of M. spicata-derived Ag-NPs, positioning them as eco-friendly candidates for biomedical exploration.