| Salvia has been classified as Substances Generally Recognized as Safe by the Food and Drug Administration. It presented a fine antibacterial performance against a variety of bacteria and it can be used as potentially useful sources of antimicrobial and antioxidant compounds. Nevertheless, the application of Salvia essential oil(SO) is limited due to their inherent volatility that leads to the reduction of valid time. In order to exploit the antimicrobial efficacy of SO, encapsulation within polymeric liposomal systems was undertaken. The liposomes were subsequently polymer-coated in order to further enhance the stability of the formulations. Based on the damage effect of pore-forming toxin on cell membrane, α-toxin secreted from S. aureus can be used to trigger the release of SO from nanoliposomes to achieve antibacterial effect on S. aureus biofilm. The SO nanoliposomes can transport SO to target sites and maintain a higher antimicrobial concentration than conventional dosage forms.(1) The chemical compositions of SO were determined by GC-MS, the result indicaded that the main composition was linalyl acetate(74.562%). To evaluate the antimicrobial activity of SO, the MIC and MBC of seven pathogens were tested. For the seven bacterial strains, the MICs values ranged from 0.25 to 0.5 mg/m L, and the MBCs values varied from 0.5 to 1 mg/mL. The kill time analysis exhibited satisfactory antimicrobial activity, after treated for 2 h, above 99.999% reductions in population were achieved both in E. coli and S. aureus. Based on above results, the SO showed very well antibacterial effect on the foodborne pathogen. Through the above experimental results, the main antibacterial mechanism of SO can be summarized. The chemical compounds in SO are able to destroy the membranes of bacterial cells. The intracellular substances, such as ATP and DNA, lose through impaired cell membrane. At the same time, SO gets inside bacteria cell through impaired cell membrane. It inhibits the synthesis of ATP and nucleic acid.(2) Furthermore, the anti-biofilm activity of SO was tested. The ESEM images showed that SO had a well anti-biofilm activity of S. aureus biofilms. The anti-biofilm activity was tested both by MTT staining method and plate colony-counting method, and both methods exhibited good correlation. The 2 mg/m L SO effectively inhibeted the biofilms grew on stainless steel and 3 mg/m L SO total inhibeted the biofilms both on plastic chips and glass chips. More than 99.99% of viable S. aureus biofilms grew on stainless steel chips, plastic chips and glass chips was reduced after 8 mg/m L SO treated for 8 h.(3) SO nanoliposomes were prepared according to the thin film hydration method in order to increase its stability and the SO nanoliposomes were characterized. In our study, the particle size of SO nanoliposomes was 188.5 ± 6.55 nm, the PDI was 0.189 ± 0.02, the surface zeta potential was 0.189 ± 0.021 mV, the turbidity value was 824 ± 32.5 NTU and the pH was 6.23 ± 0.02. Finally, the encapsulation efficiency we calculated was 46.51 ± 0.67%. The results indicated that the SO nanoliposomes were spherical, uniformly and dispersed without aggregation phenomenon.(4) GC-MS and plate colony-counting method had been utilized to observe the controlled release of SO from nanoliposomes incubated with S.aureus. It indicated that SO was released from nanoliposomes under the action of α-toxin, which was concordant with our hypothesis. Lastly, the antibacterial effect of SO nanoliposomes against S. aureus biofilms in milk environment were investigated, the results showed the number of viable S. aureus grew on stainless steel, plastic chips and glass chips were reduced by 99.89%, 99.993% and 99.81% in 15 th d respectively. Furthermore, compared to SO, the SO nanoliposomes could affect the S. aureus biofilm long term even for 6 days and improved the anti-biofilm activity. |
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