da Silva Rafael T P, Petri Marcos V, Valencia Estela Y, Camargo Pedro H C, de Torresi Susana I C, Spira Beny
Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Brazil.
Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, Brazil.
Photodiagnosis Photodyn Ther. 2020 Sep;31:101908. doi: 10.1016/j.pdpdt.2020.101908. Epub 2020 Jul 5.
The interaction of metallic nanoparticles with light excites a local surface plasmon resonance (LSPR). This phenomenon enables the transfer of hot electrons to substrates that release Reactive Oxygen Species (ROS). In this context, the present study aimed at enhancing the antibacterial effect of citrate-covered silver nanoparticles (AgNPs) by LSPR excitation with visible LED. AgNPs possess excellent antimicrobial properties against Pseudomonas aeruginosa, one of the most refractory organisms to antibiotic treatment. The Minimum Inhibitory Concentration (MIC) of the AgNPs was 10 μg/ml under dark conditions and 5 μg/ml under light conditions. The combination of light and AgNPs led to 100% cell death after 60 min. Flow cytometry quantification showed that bacteria treated with LSPR-stimulated AgNPs displayed 4.8 times more ROS. This significant increase in ROS possibly accounts for most of the antimicrobial effect of the AgNPs. In addition, light exposition caused a small release of silver ions (0.4%) suggesting that silver ions may play a secondary role in P. aeruginosa death. Overall, the results presented here show that LSPR stimulation of AgNPs by visible light enhances the antimicrobial activity of silver nanoparticles and can be an alternative for the treatment of topic infections caused by antibiotic-resistant bacteria such as P. aeruginosa.
金属纳米颗粒与光的相互作用激发了局部表面等离子体共振（LSPR）。这种现象使得热电子能够转移到释放活性氧（ROS）的底物上。在此背景下，本研究旨在通过用可见光发光二极管进行LSPR激发来增强柠檬酸盐包覆的银纳米颗粒（AgNPs）的抗菌效果。AgNPs对铜绿假单胞菌具有优异的抗菌性能，铜绿假单胞菌是对抗生素治疗最具抗性的微生物之一。在黑暗条件下，AgNPs的最低抑菌浓度（MIC）为10μg/ml，在光照条件下为5μg/ml。光照和AgNPs的组合在60分钟后导致100%的细胞死亡。流式细胞术定量分析表明，用LSPR刺激的AgNPs处理的细菌产生的ROS多4.8倍。ROS的显著增加可能是AgNPs抗菌作用的主要原因。此外，光照导致少量银离子释放（0.4%），这表明银离子在铜绿假单胞菌死亡中可能起次要作用。总体而言，此处呈现的结果表明，可见光对AgNPs的LSPR刺激增强了银纳米颗粒的抗菌活性，并且可以作为治疗由铜绿假单胞菌等耐药细菌引起的局部感染的一种替代方法。
