Issue 6, 2009

Uptake pathways of anionic and cationic photosensitizers into bacteria

Abstract

The effect of divalent cations (calcium and magnesium) and a permeabilizing agent (EDTA) on the uptake of a cationic photosensitizer (PS), methylene blue (MB), and two anionic PSs, rose bengal (RB) and indocyanine green (ICG), by Gram-positive Enterococcus faecalis and Gram-negative Actinobacillus actinomycetemcomitans was examined. The possible roles of multidrug efflux pumps and protein transporters in photosensitizer uptake were assessed in E. faecaliscells by studies using an efflux pump inhibitor (verapamil) and trypsin treatment respectively. Divalent cations enhanced the uptake and photodynamic inactivation potential of both RB and ICG in E. faecalis and A. actinomycetemcomitans, while they decreased the uptake and bacterial killing by MB. Verapamil increased the uptake of RB (possibly due to efflux pump inhibition), whereas trypsin treatment resulted in significant decrease in RB and ICG uptake. The results suggested that the uptake of anionic PSs by bacterial cells may be mediated through a combination of electrostatic charge interaction and by protein transporters, while the uptake of cationic PSs, as previously reported, is mediated by electrostatic interactions and self promoted uptake pathways.

Graphical abstract: Uptake pathways of anionic and cationic photosensitizers into bacteria

Article information

Article type
Paper
Submitted
09 Jun 2008
Accepted
12 Mar 2009
First published
31 Mar 2009

Photochem. Photobiol. Sci., 2009,8, 788-795

Uptake pathways of anionic and cationic photosensitizers into bacteria

S. George, M. R. Hamblin and A. Kishen, Photochem. Photobiol. Sci., 2009, 8, 788 DOI: 10.1039/B809624D

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