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 μs 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.

Photodynamic inactivation ofAeromonas hydrophilaby cationic phthalocyanines with different hydrophobicity

“…3). Similar findings were observed by other authors, who obtained dark toxicity for the longer carbohydrate chain porphyrin derivatives (Reddi et al , 2002). The relatively long saturated alkyl chains (C>14) of the macromolecular ring can interact with hydrophobic areas in the cell membrane, inducing a marked alteration of the native three‐dimensional architecture and impairing specific metabolic processes and normal function of bacterial cells.…”

Porphyrin derivatives as photosensitizers for the inactivation ofBacillus cereusendospores

“…Also, it has been demonstrated that the efficiency of the inactivation of micro‐organisms by photosensitizers, namely of the porphyrinic type, is strongly dependent on structural features, such as charge number, charge distribution and amphiphilicity (Merchat et al. 1996; Reddi et al. 2002; Hamblin and Hasan 2004; Tomé et al.…”

“…It has been demonstrated that structural alterations consisting of the addition of positive charges and/or functional groups to a PS may increase its effectiveness in the inactivation of particular bacterial groups (Merchat et al. 1996; Reddi et al. 2002; Hamblin and Hasan 2004; Tomé et al.…”

Antibacterial effect of cationic porphyrazines and anionic phthalocyanine and their interaction with plasmid DNA

“…Among the novel developed antibacterial agents, porphyrin complexes and their derivatives have attracted much attention due to their presence in natural systems which make them ideal candidates for use in medical applications [5][6][7]. Phthalocyanines differ from porphyrins by having nitrogen atoms link the individual pyrrol units.…”