Porphyrin-based cationic amphiphilic photosensitisers as potential anticancer, antimicrobial and immunosuppressive agents

Abstract

Photodynamic therapy (PDT) combines a photosensitiser, light and molecular oxygen to induce oxidative stress that can be used to kill pathogens, cancer cells and other highly proliferative cells. There is a growing number of clinically approved photosensitisers and applications of PDT, whose main advantages include the possibility of selective targeting, localised action and stimulation of the immune responses. Further improvements and broader use of PDT could be accomplished by designing new photosensitisers with increased selectivity and bioavailability. Porphyrin-based photosensitisers with amphiphilic properties, bearing one or more positive charges, are an effective tool in PDT against cancers, microbial infections and, most recently, autoimmune skin disorders. The aim of the review is to present some of the recent examples of the applications and research that employ this specific group of photosensitisers. Furthermore, we will highlight the link between their structural characteristics and PDT efficiency, which will be helpful as guidelines for rational design and evaluation of new PSs.

Keywords: Cancer; Infection; Photodynamic therapy; Photosensitiser; Porphyrin.

Fig. 1

Scheme of the photophysical and photochemical processes involved in PDT

Fig. 2

Basic structure of porphyrin and the most common porphyrin-type photosensistisers

Fig. 3

Structures of some cationic amphiphilic porphyrins: zinc(II) meso-tetrakis(N-n-hexylpyridinium-3-yl)porphyrin (ZnTnHex-3-PyP); 5,10,15-tris(N-methyl-4-pyridyl)-20-(N-tetradecyl-4-pyridyl)porphyrin (TMPyP4-C14); 5-(4-trifluoromethylphenyl)-10,15,20-tris(4-trimethylammoniumphenyl)porphyrin (TFAP(3+))