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Photochem Photobiol Sci. 2010 Dec;9(12):1613-20. doi: 10.1039/c0pp00146e. Epub 2010 Oct 8.

Effective photoinactivation of Gram-positive and Gram-negative bacterial strains using an HIV-1 Tat peptide-porphyrin conjugate.

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National Medical Laser Centre, Division of Surgery and Interventional Science, UCL Medical School, University College London, Charles Bell House, 67-73 Riding House St, London, UKW1W 7EJ.


Given that cell-penetrating peptides (CPP) are cationic and often amphipathic, similar to membrane-active antimicrobial peptides, it may be possible to use CPP conjugation to improve the delivery of photosensitisers for antimicrobial photodynamic therapy (antimicrobial PDT). We investigated the possibility of using a Tat peptide to deliver the photosensitiser, tetrakis(phenyl)porphyrin (TPP) and kill bacteria. The Tat peptide is a positively-charged mammalian cell-penetrating peptide with potent antimicrobial activity but no haemolytic activity. Fluorescence spectroscopy revealed that the bioconjugate can bind to and/or be incorporated into all bacterial species tested. All species were susceptible to the Tat-porphyrin, with the bactericidal effect being dependent on both the concentration and the light dose. Using the highest light dose, treatment with the Tat-porphyrin achieved reductions of 6.6 log(10) and 6.37 log(10) in the viable counts of Staphylococcus aureus and Streptococcus pyogenes, and reductions of 5.74 log(10) and 6.6 log(10) in the viable counts of Pseudomonas aeruginosa and Escherichia coli. Moreover, the Tat moiety appears to confer antimicrobial properties to the conjugate, particularly for the Gram positive strains, based on the observation of dark toxicity using 1 μM of Tat-porphyrin. Finally, the conjugate induced membrane destabilization by synergistic action of the peptide and PDT, resulting in carboxyfluorescein leakage from bacterial membrane-mimicking liposomes. These findings demonstrate that the use of CPP to deliver a photosensitiser is an effective way of improving the uptake and the treatment efficacy of antimicrobial PDT.

[Indexed for MEDLINE]

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