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Oral hygiene is fundamental to maintaining overall health, and antimicrobial mouthwashes play an important role in preventing oral microbial infections. This study aimed to develop and evaluate a natural antibacterial mouthwash based on a nanoemulsion incorporating green-synthesized silver nanoparticles (AgNPs) and Origanum vulgare (oregano) essential oil. The AgNPs were synthesized using epigallocatechin gallate (EGCG) derived from green tea as a reducing and stabilizing agent, while oregano essential oil, rich in carvacrol and thymol, served as the primary natural antimicrobial component. The effects of oregano oil concentration and nanosilver addition on the characteristics, stability, and antibacterial activity of an oregano oil-nanosilver nanoemulsion using Tween 80 as a surfactant were studied.
The nanoemulsion formulation was optimized by varying the concentrations of oregano oil and Tween 80. Selected formulations containing 0.5% and 1.0% oregano oil, with or without 10% AgNP dispersion, were characterized for pH, particle size, polydispersity index (PDI), organoleptic properties during eight weeks of storage, and antibacterial activity against Escherichia coli and Staphylococcus aureus. All formulations exhibited acidic pH values ranging from 3.6 to 4.5, which remained stable throughout the storage period. The nanoemulsions showed mean particle sizes of 20–45 nm with PDI values below 0.30, indicating a homogeneous nanoscale dispersion. The formulation containing 1.0% oregano oil and AgNPs exhibited particle aggregation after four weeks, whereas formulations containing 0.5% oregano oil, both with and without AgNPs, maintained physical stability over eight weeks. The incorporation of AgNPs significantly enhanced the antibacterial activity of the oregano oil nanoemulsion against both test microorganisms compared with the corresponding formulation without nanoparticles.
These findings demonstrate that the combination of green-synthesized AgNPs and oregano essential oil produces a stable nanoemulsion with enhanced antibacterial efficacy, highlighting its potential as a sustainable and effective natural mouthwash for oral healthcare applications.
Keywords: oregano oil, nanosilver, mouthwash, stability, antibacterial activity.
