Photophysical Properties and Antibacterial Activity of Meso-substituted Cationic Porphyrins¶

Abstract

A series of derivatives of 5,10,15,20-tetrakis-(4-N-methylpyridyl)-porphine, where one N-methyl group was replaced by a hydrocarbon chain ranging from C6 to C22, were characterized for their photophysical and photosensitizing properties. The absorption and fluorescence features of the various compounds in neutral aqueous solutions were typical of largely monomeric porphyrins, with the exception of the C22 derivative, which appeared to be extensively aggregated. This was confirmed by the very low triplet quantum yield and lifetime of the C22 derivative as compared with 0.2-0.7 quantum yields and 88-167 micros lifetimes for the other porphyrins. The photophysical properties and photosensitizing activity toward N-acetyl-L-tryptophanamide of the C22 porphyrin became comparable to those typical of the other derivatives in 2% aqueous sodium dodecyl sulfate, where the C22 compound is fully monomerized. All the porphyrin derivatives exhibited at micromolar concentrations photoinactivation activity against both Staphylococcus aureus and Escherichia coli, even though the gram-negative bacteria were markedly less photosensitive. The photosensitizing efficiency was influenced by (1) the amount of cell-bound porphyrin, which increased with increasing length of the hydrocarbon chain; and (2) the tendency to undergo partial aggregation in the cell, which seems to be especially important for the C22 derivative.

Effects of environment on the photophysical characteristics of mesotetrakis methylpyridiniumyl porphyrin (TMPyP)

“…Moreover, simple symmetric porphyrins are low-cost materials and depending on the application, demonstrate high efficiency, such as for optical devices [1][2][3][4][5]. Specifically, porphyrins/micelles interaction is of interest because micelles can been considered as a model of biological membrane [18][19][20], and, also because they as a matrix for active optical molecular systems [13,21].…”

“…TMPyP has also demonstrated anti-HIV [21,23] and antibacterial activity [18], and it was used as active compound for singlet oxygen imaging of single cells [19] and for singlet oxygen photosensitization in skin fibroblasts [20]. Although TMPyP has already been demonstrated to present nonlinear optical response [24], there is a lack of information how this molecule interacts with the distinct environments, such as organic solvents and micelles, and consequently, how its excited state dynamics is altered.…”

Photodynamic antimicrobial chemotherapy (PACT) for the treatment of malaria, leishmaniasis and trypanosomiasis

“…The effectiveness of a photo-decontamination depends on a series of factors including the type of microorganisms as well as the type of photosensitisers and the reaction medium. It is often relatively straightforward to demonstrate microbial selectivity, given the biological staining heritage of many photoantimicrobial agents (5,6,(27)(28)(29).…”

Second Test to Send Abstracts

“…The positively charged polylysine could potentially facilitate binding to the negatively charged bacterial surface, thus allowing the photo-sensitizer to selectively target bacterial cells [1]. Various cationic porphyrins have been used as remarkable antimicrobial agents in PACT [15][16][17][18][19][20].…”