Ultrasound-Assisted Formation and Investigation of Sodium Alginate-Stabilized Clove Essential Oil Nanoemulsions with Enhanced Antimicrobial Activity

Ultrasound-assisted emulsification is an effective approach for producing stable nanoemulsions containing bioactive essential oils. In this study, sodium alginate-stabilized clove essential oil (CEO) nanoemulsions were prepared by varying the ultrasonic power (200–500 W), sonication time (60–300 s), and Tween 80 concentration (1–2%, v/v). The effects of these processing parameters on droplet size, the polydispersity index (PDI), zeta potential, physicochemical stability, and antimicrobial activity were systematically investigated. The nanoemulsions were characterized by dynamic light scattering, ATR-FTIR spectroscopy, Raman microscopy, and emulsion stability analysis. Among the investigated formulations, the nanoemulsion prepared at 400 W for 150 s using 1% (v/v) Tween 80 exhibited the most favorable characteristics, with a mean droplet size of 167.3 ± 5.2 nm, a PDI of 0.30 ± 0.01, and a zeta potential of −60 ± 1.7 mV, indicating excellent colloidal stability. ATR-FTIR and Raman microscopy confirmed the presence of clove essential oil (CEO) in the dispersed oil droplets of the nanoemulsion and suggested intermolecular interactions, mainly hydrogen bonding, between CEO and alginate. The selected formulation exhibited broad-spectrum antimicrobial activity, with inhibition zones of 30.0 ± 0.1 mm against Candida albicans, 15 ± 0.1 mm against Bacillus subtilis, and 16 ± 0.1 mm against Escherichia coli. It also showed low minimum inhibitory concentrations (MICs), ranging from 0.312% to 5% (v/v), with the highest antimicrobial efficacy observed against C. albicans (MIC = 0.312% v/v), followed by B. subtilis and E. coli (MIC = 0.625% v/v). In addition, a cytotoxicity assay showed no significant cytotoxic effect under the tested conditions. Overall, these results demonstrate the potential of ultrasound-assisted sodium alginate-stabilized clove essential oil nanoemulsions as promising antimicrobial systems for further encapsulation and incorporation into bio-based antimicrobial materials for functional coatings and textile-related applications.