Essential oil–encapsulated SiO2 nanocapsules for the treatment of bacterial biofilms formed on food-contact surfaces

Litsea cubeba essential oil (EO)-encapsulated SiO 2 (SiO 2 -EO) nanocapsules were fabricated by in situ biosilicification for the treatment of biofilms on food-contact surfaces. By optimizing the synthesis conditions (0.5 mg/mL EO and 50 mM silicic acid), SiO 2 -EO nanocapsules exhibited a uniform size distribution (150–200 nm) with a distinct core–shell structure. The characterization of nanocapsules was elucidated using a scanning electron microscope (SEM), transmission electron microscope, Fourier transform infrared, and x-ray diffraction analyses. The minimal inhibitory concentrations of SiO 2 -EO nanocapsules were 5 and 1.25 mg/mL for Escherichia coli and Staphylococcus aureus , respectively. Compared to free EO, the SiO 2 -EO nanocapsules showed more significant inhibition activity against both Gram-negative and Gram-positive bacterial biofilms. Confocal experiments and SEM demonstrated that the nanocapsules efficiently penetrate biofilms within 30 min and deliver EO to destroy the membrane structure of bacteria. Eventually, SiO 2 -EO nanocapsules were also applied to four kinds of food-contact surfaces. The populations in biofilms exposed to 2.5 mg/mL of nanocapsules decreased 1.51–1.56 log CFU/cm 2 and 2.15–2.22 log CFU/cm 2 for E. coli and S. aureus , respectively. This study provides an innovative strategy to treat bacterial biofilms with EO-based nanocomposites.