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Issue 1, 2006
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Enhancement of the photodynamic activity of tri-cationic porphyrins towards proliferating keratinocytes by conjugation to poly-S-lysine

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Abstract

A fast uptake of the tri-cationic 5-(4-carboxyphenyl)-10,15,20-tris(4-methylpyridinium-4-yl)porphyrin tri-iodide (P-H), independent of the presence or absence of proteins in the culture medium, occurs during incubation of NCTC 2544 human keratinocytes with this porphyrin. By contrast, the uptake of the poly-S-lysine conjugate (P-(Lys)n) is faster in serum-free medium than in the supplemented medium suggesting that P-(Lys)n interacts with serum proteins. The P-(Lys)n uptake is almost an order of magnitude greater than that of P-H in serum-free or supplemented culture medium. With histidine as a specific probe of type II photodynamic reactions, the relative photosensitizing effectiveness of the conjugate is only one fourth that of P-H. Nevertheless, the photocytotoxicity of the conjugate is strongly enhanced as compared to that of P-H as a result of its larger uptake. Thus, the doses achieving 50% of photocytotoxicity after incubation with 5 µM of the conjugate and its parent cationic porphyrin are about 20 min and 1 h, respectively. Similarly, the initial rate of the cell lipid peroxidation induced by photosensitization with P-(Lys)n is about 8 times higher than that obtained with P-H. Fluorescence microscopy reveals that P-H is more diffusely located in the cytoplasm than P-(Lys)n which seems to accumulate in lysosome-like structures. Little if any staining of the nucleus is observed with both photosensitizers.

Graphical abstract: Enhancement of the photodynamic activity of tri-cationic porphyrins towards proliferating keratinocytes by conjugation to poly-S-lysine

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Publication details

The article was received on 09 Sep 2005, accepted on 11 Oct 2005 and first published on 25 Nov 2005


Article type: Paper
DOI: 10.1039/B512841B
Citation: Photochem. Photobiol. Sci., 2006,5, 126-133
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    Enhancement of the photodynamic activity of tri-cationic porphyrins towards proliferating keratinocytes by conjugation to poly-S-lysine

    J. Nuno Silva, J. Haigle, J. P. C. Tomé, M. G. P. M. S. Neves, A. C. Tomé, J. Mazière, C. Mazière, R. Santus, J. A. S. Cavaleiro, P. Filipe and P. Morlière, Photochem. Photobiol. Sci., 2006, 5, 126
    DOI: 10.1039/B512841B

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