Nanoparticle-stabilized encapsulation of borneol and citral: Physicochemical characteristics, storage stability, and enhanced antibacterial activities.

Combinations of phytochemical(s) and engineered nanoparticles have attracted immense research interest due to their superior antimicrobial effects against contaminations. Herein, a Pickering emulsion is developed with capsulized phytochemicals including borneol and citral (BC-Cap) stabilized by hydrophilic amine-functionalized silica nanoparticles (SiO2 ─NH2 NPs). The droplet sizes of Pickering emulsion were 5.2 ± 1.4 µm under the condition that the concentrations of SiO2 ─NH2 NPs ranged from 0.6 to 1.2 wt.%, and the emulsion showed desirable stability during storage at 40°C for 365 days. In addition, the antibacterial and antibiofilm activities of the Pickering emulsion were investigated. The antibacterial effect of BC-Cap increased by two- to fourfold compared with citral or borneol alone. Treatment of BC/BC-Cap for 4 h eliminated the formation of biofilms generated by Listeria monocytogenes (at 5/1.25 mg/ml; 2 × MIC concentration) and Pseudomonas aeruginosa (at 5/2.5 mg/ml; 2 × MIC concentration). Further mechanistic studies revealed that the antibiofilm effects of BC-Cap were attributed to its ability to increase the porosity and lytic effects on the cell membrane of bacteria. Findings from the current study support the antibacterial and antibiofilm effects of BC-Cap Pickering emulsion as a promising food additive. PRACTICAL APPLICATION: The Pickering emulsion has potential applications as bacteriostatic agent in packaging materials and general surface disinfectant. The combination of borneol and citral is stabilized by hydrophilic amine-functionalized silica nanoparticles (SiO2 ─NH2 NPs). With the synergistic effects of borneol and citral, the Pickering emulsion shows a promising elimination effect against the formation of biofilms produced by Listeria monocytogenes and Pseudomonas aeruginosa.