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Synthesis and antibacterial activity of novel cationic BODIPY photosensitizers

Paper ID Volume ID Publish Year Pages File Format Full-Text
30740 44500 2012 8 PDF Available
Title
Synthesis and antibacterial activity of novel cationic BODIPY photosensitizers
Abstract

BODIPYs are versatile dyes never tested before in photodynamic application against prokaryotes. We specifically synthesized two cationic BODIPYs (compounds 3 and 4) with structural features suitable for this pourpose. The novel BODIPYs are both characterized by the presence of one pyridinium cationic group on position 8 and two iodine atoms on 2,6-positions of the dipyrrolylmethene structure, thus ensuring solubility in 1/1 water/organic solvent mixture and a good singlet oxygen formation rate. These two photosensitizers differ only in the moiety linked on pyridine nitrogen atom as 3 and 4 bear a methyl and a benzyl group, respectively. BODIPYs 3 and 4 were tested against two bacterial model strains, the Gram positive Staphylococcus xylosus and the Gram negative Escherichia coli.Despite the small structural modification between 3 and 4, a remarkable difference in photocatalyzed efficacy against the model microorganisms was observed. In particular methylated compound 3 was found much more efficient with respect to the benzylated one (4). As consequence, in-depth examination of the antibacterial activity was performed using the more efficient compound 3. A high degree of phototoxicity (>6 log units) was observed with the photosensitizer 0.5 μM against S. xylosus and 5.0 μM against E. coli, following 5 min irradiation with a green LED device (light dose 1.38 J/cm2). No dark toxicity was observed up to 40 μM. Further studies indicate that the phototoxic efficacy induced by BODIPY 3 depends both on its concentration and on light dose, which can be specifically modulated to achieve the eradication of the tester strains.

► Synthesis of unprecedented cationic BODIPYs (PSs) and physico-chemical data. ► BODIPY skeleton featuring two iodine atoms and one pyridinium group. ► Highly efficient antimicrobial phodynamic therapy on E. coli and S. xylosus. ► 7 log units decrease of survivors after 10 min of incubation and 5 min. green LED irradiation (1.38 J/cm2).

Keywords
CFUs, colony forming units; LED, light emitting diode; MBC, minimal bactericidal concentration; MIC, minimal inhibitory concentration; PACT, photodynamic antimicrobial chemo-therapy; PB, phosphate buffer; PDT, photodynamic therapy; PS, photosensitizer; RT
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Synthesis and antibacterial activity of novel cationic BODIPY photosensitizers
Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology B: Biology - Volume 114, 3 September 2012, Pages 44–51
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering