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Fast and effective photodynamic inactivation of multiresistant bacteria by cationic riboflavin derivatives.

ABSTRACT: Photodynamic inactivation of bacteria (PIB) proves to be an additional method to kill pathogenic bacteria. PIB requires photosensitizer molecules that effectively generate reactive oxygen species like singlet oxygen when exposed to visible light. To allow a broad application in medicine, photosensitizers should be safe when applied in humans. Substances like vitamin B2, which are most likely safe, are known to produce singlet oxygen upon irradiation. In the present study, we added positive charges to flavin derivatives to enable attachment of these molecules to the negatively charged surface of bacteria. Two of the synthesized flavin derivatives showed a high quantum yield of singlet oxygen of approximately 75%. Multidrug resistant bacteria like MRSA (Methicillin resistant Staphylococcus aureus), EHEC (enterohemorrhagic Escherichia coli), Pseudomonas aeruginosa, and Acinetobacter baumannii were incubated with these flavin derivatives in vitro and were subsequently irradiated with visible light for seconds only. Singlet oxygen production in bacteria was proved by detecting its luminescence at 1270 nm. After irradiation, the number of viable bacteria decreased up to 6 log10 steps depending on the concentration of the flavin derivatives and the light dosimetry. The bactericidal effect of PIB was independent of the bacterial type and the corresponding antibiotic resistance pattern. In contrast, the photosensitizer concentration and light parameters used for bacteria killing did not affect cell viability of human keratinocytes (therapeutic window). Multiresistant bacteria can be safely and effectively killed by a combination of modified vitamin B2 molecules, oxygen and visible light, whereas normal skin cells survive. Further work will include these new photosensitizers for topical application to decolonize bacteria from skin and mucosa.

SUBMITTER: Maisch T

PROVIDER: S-EPMC4254278 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Fast and effective photodynamic inactivation of multiresistant bacteria by cationic riboflavin derivatives.

Maisch Tim T Eichner Anja A Späth Andreas A Gollmer Anita A König Burkhard B Regensburger Johannes J Bäumler Wolfgang W

PloS one 20141203 12

Photodynamic inactivation of bacteria (PIB) proves to be an additional method to kill pathogenic bacteria. PIB requires photosensitizer molecules that effectively generate reactive oxygen species like singlet oxygen when exposed to visible light. To allow a broad application in medicine, photosensitizers should be safe when applied in humans. Substances like vitamin B2, which are most likely safe, are known to produce singlet oxygen upon irradiation. In the present study, we added positive charg ...[more]

PMID: 25469700

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Project description:It is known that multiple cationic charges are required to produce broad-spectrum antimicrobial photosensitizers (PS) for photodynamic inactivation (aPDI) or photodynamic therapy of bacteria and fungi. In the present study we describe the synthesis and aPDI testing of a set of derivatives prepared from the parent pheophytin molecule with different numbers of attached side arms (1-3) each consisting of five quaternized cationic groups (pentacationic), producing the corresponding [Zn2+]pheophorbide-a-N(C2N+C1C3)5 (Zn-Phe-N5+, 5 charges), [Zn2+]chlorin e6-[N(C2N+C1C3)5]2 (Zn-Chl-N10+, 10 charges) and [Zn2+]mesochlorin e6-[N(C2N+C1C3)5]3 (Zn-mChl-N15+, 15 charges). Moreover, a conjugate between Zn-Phe-N5+ and the antibiotic vancomycin called Van-[Zn2+]-m-pheophorbide-N(C2N+C1C3)5 (Van-Zn-mPhe-N5+) was also prepared. The aPDI activities of all compounds were based on Type-II photochemistry (1O2 generation). We tested these compounds against Gram-positive methicillin-resistant Staphylococcus aureus (MRSA), Gram-negative Escherichia coli, and the fungal yeast Candida albicans. All three compounds were highly active against MRSA, giving eradication (?6 logs of killing) with <1.0 ?M and 10 J cm-2 of 415 nm light. The order of activity was Zn-Phe-N5+ > Zn-Chl-N10+ > Zn-mChl-N15+. In the case of E coli the activity was much lower (eradication was only possible with 50 ?M Zn-mChl-N15+ and 20 J cm-2). The order of activity was the reverse of that found with MRSA (Zn-mChl-N15+ > Zn-Chl-N10+ > Zn-Phe-N5+). Activity against C. albicans was similar to E. coli with Zn-mChl-N15+ giving eradication. The activity of Van-Zn-mPhe-N5+ was generally lower than that of Zn-Phe-N5+ (except for E. coli). Red (660 nm) light was also effective as might be expected from the absorption spectra. An initial finding that Van-Zn-mPhe-N5+ might have higher activity against vancomycin resistant Enterococcus fecium (VRE) strains (compared to vancomycin sensitive strains) was disproved when it was found that VRE strains were also more sensitive to aPDI with Zn-Phe-N5+. The minimum inhibitory concentrations of Van-Zn-mPhe-N5+ were higher than those of Van alone, showing that the antibiotic properties of the Van moiety were lessened in the conjugate. In conclusion, Zn-Phe-N5+ is a highly active PS against Gram-positive species and deserves further testing. Increasing the number of cationic charges increased aPDI efficacy on C. albicans and Gram-negative E. coli.

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Fast and effective photodynamic inactivation of multiresistant bacteria by cationic riboflavin derivatives.

Publications

Fast and effective photodynamic inactivation of multiresistant bacteria by cationic riboflavin derivatives.

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