School of Food and Bioengineering, Hefei University of Technology, Hefei 230009, China.
School of Food and Bioengineering, Hefei University of Technology, Hefei 230009, China; Engineering Research Center of Bio-process, Ministry of Education, Hefei University of Technology, 193 Tunxi Road, Hefei 230009, China.
Food Res Int. 2022 Jun;156:111141. doi: 10.1016/j.foodres.2022.111141. Epub 2022 Mar 16.
Staphylococcus aureus (S. aureus) is a foodborne pathogen that endangers human health worldwide. Antimicrobial photodynamic inactivation (aPDI), mediated by titanium dioxide nanoparticles (TiONP), was recently used to control the growth of S. aureus, however, UV illumination had to be offered to initiate the photodynamic reaction. To overcome this drawback, a dual-photon system was established here based on TiONP and hypocrellin B (HB), a natural pigment with photocatalyst activity. Irradiated at the visible light (9 J/cm) at the wavelength of 460 nm, the joint use of both photosensitizers (PS) caused a substantial decline of staphylococcal survival, reaching a maximum decrease of 4 ∼ 5 logs. When 10 nM HB and 100 µM TiONP were applied, a synergistic photokilling effect was achieved, only in the mixed phase of anatase/rutile, Degussa P25. Regarding the antimicrobial mechanisms, it was found that the membrane integrity of S. aureus was heavily disrupted, surface morphology was altered, intracellular substances like potassium and DNA were leaked, and biofilm formation was significantly circumvented due to the excitation of sensitized PS. In terms of antioxidant responsiveness of S. aureus, qPCR results showed that a series of genes encoding the membrane-associated cell death effectors were deregulated. Among them, LrgA was recognized as a key responsive element, due that the mutant strain harboring a constitutively-expressed LrgA strengthened the bactericidal effect of aPDI. Finally, the dual-photon strategy lowered the microbial contamination in the tested apple with its quality maintained, under the condition of visible light. Taken together, a new dual-photon system based on TiONP and HB was constructed and validated in photokilling S. aureus, providing a well-adapted technique to maintain food safety.
金黄色葡萄球菌（S. aureus）是一种食源性病原体，对全球人类健康构成威胁。基于二氧化钛纳米颗粒（TiONP）的抗菌光动力灭活（aPDI）最近被用于控制金黄色葡萄球菌的生长，但需要提供紫外线照射来启动光动力反应。为了克服这一缺点，本研究建立了一种基于 TiONP 和竹红菌素 B（HB）的双光子系统，HB 是一种具有光催化剂活性的天然色素。在 460nm 波长的可见光（9 J/cm）下辐照时，两种光敏剂（PS）的联合使用导致金黄色葡萄球菌存活率大幅下降，最大下降幅度达到 4~5 个对数级。当使用 10 nM HB 和 100 µM TiONP 时，在锐钛矿/金红石混相的 Degussa P25 中实现了协同光杀伤效应。关于抗菌机制，发现金黄色葡萄球菌的膜完整性受到严重破坏，表面形态发生改变，钾和 DNA 等细胞内物质泄漏，生物膜形成也因敏化 PS 的激发而受到显著阻碍。就金黄色葡萄球菌的抗氧化反应性而言，qPCR 结果表明，一系列编码与膜相关的细胞死亡效应物的基因被下调。其中，LrgA 被认为是一个关键的响应元件，因为携带组成型表达 LrgA 的突变株增强了 aPDI 的杀菌作用。最后，该双光子策略在可见光条件下降低了测试苹果中的微生物污染，同时保持了其质量。总之，构建并验证了基于 TiONP 和 HB 的新型双光子系统在光杀伤金黄色葡萄球菌中的应用，为维持食品安全提供了一种适应性强的技术。
