Abstract

Ultraviolet-C light-emitting diodes (UV-C LEDs) are an emerging technology for decontamination applications in different sectors. In this study, the inactivation of bacterial biofilms was investigated by applying an UV-C LED emitting at 280 nm and by measuring both the influence of the initial cell density (load) and presence of an extracellular matrix (biofilm). Two bacterial strains exposing diverging matrix structures and biochemical compositions were used: Pseudomonas aeruginosa and Leuconostoc citreum. UV-C LED irradiation was applied at three UV doses (171 to 684 mJ/cm²) on both surface-spread cells and on 24-h biofilms and under controlled cell loads, and bacterial survival was determined. All surface-spread bacteria, between 10⁵ and 10⁹ CFU/cm², and biofilms at 10⁸ CFU/cm² showed that bacterial response to irradiation was dose-dependent. The treatment efficacy decreased significantly for L. citreum surface-spread cells when the initial cell load was high, while no load effect was observed for P. aeruginosa. Inactivation was also reduced when bacteria were grown under a biofilm form, especially for P. aeruginosa: a protective effect could be attributed to abundant extracellular DNA and proteins in the matrix of P. aeruginosa biofilms, as revealed by Confocal Laser Scanning Microscopy observations. This study showed that initial cell load and exopolymeric substances are major factors influencing UV-C LED antibiofilm treatment efficacy.

Key points

• Bacterial cell load (CFU/cm²) could impact UV-C LED irradiation efficiency

• Characteristics of the biofilm matrix have a paramount importance on inactivation

• The dose to be applied can be predicted based on biofilm properties

Graphical Abstract

中文翻译：

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细胞密度和细胞外基质成分降低了细菌生物膜对 UV-C LED 照射的敏感性

摘要

紫外线-C 发光二极管 (UV-C LED) 是一种新兴技术，适用于不同领域的净化应用。在本研究中，通过应用发射 280 nm 的 UV-C LED 并测量初始细胞密度（负载）和细胞外基质（生物膜）的影响来研究细菌生物膜的灭活。使用两种暴露不同基质结构和生化成分的细菌菌株：铜绿假单胞菌和柠檬明串珠菌。在受控细胞负荷下，对表面扩散的细胞和 24 小时生物膜应用三种 UV 剂量（171 至 684 mJ/cm ²）的 UV-C LED 照射，并测定细菌存活率。所有表面传播的细菌（10 ⁵至10 ⁹  CFU/cm ²之间）和生物膜（10 ⁸  CFU/cm ²之间）表明细菌对辐射的反应是剂量依赖性的。当初始细胞负荷较高时，柑橘表面扩散细胞的治疗效果显着下降，而铜绿假单胞菌没有观察到负荷效应。当细菌在生物膜形式下生长时，失活也会减少，特别是对于铜绿假单胞菌：如共聚焦激光扫描显微镜观察所揭示的，保护作用可能归因于铜绿假单胞菌生物膜基质中丰富的细胞外DNA和蛋白质。本研究表明，初始细胞负荷和胞外聚合物是影响 UV-C LED 抗生物膜治疗效果的主要因素。

关键点

•细菌细胞负载 (CFU/cm ² ) 可能会影响 UV-C LED 照射效率

•生物膜基质的特性对于灭活至关重要

•可根据生物膜特性预测要施用的剂量

图形概要