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Photodynamic inactivation of microorganisms sensitized by cationic BODIPY derivatives potentiated by potassium iodide


The photodynamic inactivation mediated by 1,3,5,7-tetramethyl-8-[4-(N,N,N-trimethylamino)phenyl]-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene 3 and 8-[4-(3-(N,N,N-trimethylamino)propoxy)phenyl]-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene 4 were investigated on Staphylococcus aureus, Escherichia coli and Candida albicans. In vitro experiments indicated that BODIPYs 3 and 4 were rapidly bound to microbial cells at short incubation periods. Also, fluorescence microscopy images showed the green emission of the BODIPYs bound to microbial cells. Photosensitized inactivation improved with an increase of the irradiation times. Similar photoinactivation activity was found for both BODIPYs in bacteria. The photoinactivation induced by these BODIPYs was effective for both bacteria. However, the Gram-positive bacterium was inactivated sooner and with a lower concentration of photosensitizer than Gram-negative. After 15 min irradiation, a complete eradication of S. aureus was obtained with 1 μM photosensitizer. A reduction of 4.5 log in the E. coli viability was found using 5 μM photosensitizer and 30 min irradiation. Also, the last conditions produced a decrease of 4.5 log in C. albicans cells treated with BODIPY 3, while 4 was poorly effective. On the other hand, the addition of KI was investigated on photoinactivation at different irradiation periods and salt concentrations. A smaller effect was observed in S. aureus because the photosensitizers alone were already very effective. In E. coli, photokilling potentiation was mainly found a longer irradiation periods. Moreover, the photoinactivation of C. albicans mediated by these BODIPYs was increased in presence of KI. In solution, an increase in the formation of the BODIPY triplet states was observed with the addition of the salt, due to the effect of external heavy atom. The greater intersystem crossing together with the formation of reactive iodine species induced by BODIPYs may be contributing to enhance the inactivation of microorganisms. Therefore, these BODIPYs represent interesting photosensitizers to inactivate microorganisms. In particular, BODIPY 3 in combination with KI was highly effective as a broad spectrum antimicrobial photosensitizer.

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Publication details

The article was received on 03 Jun 2017, accepted on 10 Aug 2017 and first published on 11 Aug 2017

Article type: Paper
DOI: 10.1039/C7PP00204A
Citation: Photochem. Photobiol. Sci., 2017, Accepted Manuscript
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    Photodynamic inactivation of microorganisms sensitized by cationic BODIPY derivatives potentiated by potassium iodide

    E. Reynoso, E. D. Quiroga, M. L. Agazzi, M. B. Ballatore, S. G. Bertolotti and E. N. Durantini, Photochem. Photobiol. Sci., 2017, Accepted Manuscript , DOI: 10.1039/C7PP00204A

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