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Singlet Oxygen in Antimicrobial Photodynamic Therapy: Photosensitizer-Dependent Production and Decay in E. coli
Grup d'Enginyeria Molecular, Institut Químic de Sarrià, Universitat Ramon Llull, Barcelona E-08017, Spain
Center for Biodiversity, Functional & Integrative Genomics, Faculty of Sciences, University of Lisbon, Lisbon 1749-016, Portugal
Department of Genetics, National Institute of Health Dr. Ricardo Jorge, Lisbon 1649-016, Portugal
Departamento de Quimica, Universidade de Coimbra, Coimbra P-3049535, Portugal
* Author to whom correspondence should be addressed.
Received: 25 January 2013; in revised form: 19 February 2013 / Accepted: 21 February 2013 / Published: 28 February 2013
Abstract: Several families of photosensitizers are currently being scrutinized for antimicrobial photodynamic therapy applications. Differences in physical and photochemical properties can lead to different localization patterns as well as differences in singlet oxygen production and decay when the photosensitizers are taken up by bacterial cells. We have examined the production and fate of singlet oxygen in Escherichia coli upon photosensitization with three structurally-different cationic photosensitizers, namely New Methylene Blue N (NMB), a member of the phenothiazine family, ACS268, a hydrophobic porphyrin with a single cationic alkyl chain, and zinc(II)-tetramethyltetrapyridinoporphyrazinium salt, a phthalocyanine-like photosensitizer with four positive charges on the macrocycle core. The kinetics of singlet oxygen production and decay indicate different localization for the three photosensitizers, whereby NMB appears to localize in an aqueous-like microenvironment, whereas ACS268 localizes in an oxygen-shielded site, highly reactive towards singlet oxygen. The tetracationic zinc(II) tetrapyridinoporphyrazine is extensively aggregated in the bacteria and fails to produce any detectable singlet oxygen.
Keywords: antimicrobial photodynamic therapy; cationic photosensitizers; E. coli; kinetics; photodynamic inactivation; singlet oxygen; time-resolved near-IR spectroscopy
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MDPI and ACS Style
Ragàs, X.; He, X.; Agut, M.; Roxo-Rosa, M.; Gonsalves, A.R.; Serra, A.C.; Nonell, S. Singlet Oxygen in Antimicrobial Photodynamic Therapy: Photosensitizer-Dependent Production and Decay in E. coli. Molecules 2013, 18, 2712-2725.
Ragàs X, He X, Agut M, Roxo-Rosa M, Gonsalves AR, Serra AC, Nonell S. Singlet Oxygen in Antimicrobial Photodynamic Therapy: Photosensitizer-Dependent Production and Decay in E. coli. Molecules. 2013; 18(3):2712-2725.
Ragàs, Xavier; He, Xin; Agut, Montserrat; Roxo-Rosa, Mónica; Gonsalves, António R.; Serra, Arménio C.; Nonell, Santi. 2013. "Singlet Oxygen in Antimicrobial Photodynamic Therapy: Photosensitizer-Dependent Production and Decay in E. coli." Molecules 18, no. 3: 2712-2725.