Like a Bolt from the Blue: Phthalocyanines in Biomedical Optics

Abstract

The purpose of this review is to compile preclinical and clinical results on phthalocyanines (Pcs) as photosensitizers (PS) for Photodynamic Therapy (PDT) and contrast agents for fluorescence imaging. Indeed, Pcs are excellent candidates in these fields due to their strong absorbance in the NIR region and high chemical and photo-stability. In particular, this is mostly relevant for their in vivo activation in deeper tissular regions. However, most Pcs present two major limitations, i.e., a strong tendency to aggregate and a low water-solubility. In order to overcome these issues, both chemical tuning and pharmaceutical formulation combined with tumor targeting strategies were applied. These aspects will be developed in this review for the most extensively studied Pcs during the last 25 years, i.e., aluminium-, zinc- and silicon-based Pcs.

Phthalocyanine-loaded graphene nanoplatform for imaging-guided combinatorial phototherapy

“…12,13 Therefore, the stability and spectroscopic properties of the developed PTT-PDT platform (LOGr-Pc-LHRH) were evaluated along with the corresponding controls: PTT (LOGr-LHRH) and PDT (Pc-LHRH) agents. All three studied formulations exhibited excellent solubility in the range of physiological solutions, including PBS buffer and cell culture medium with 10% FBS (Figure 2B), indicating their potential for an efficient in vivo application.…”

“…Our nanoplatform can utilize NIR excitation of a single laser irradiation within the optical transmission window of biological tissues (~650-950 nm), thereby significantly improving penetration depths and minimizing photobleaching background autofluorescence, as well as photodamage to biological specimens. 12,13,42 Despite a strong absorption signal in the NIR optical window, previously developed nanoplatforms based on hydrophobic interactions and π-π stacking between photosensitizers and graphene oxides have been characterized by drastic fluorescence quenching of the photosensitizer and a significant decrease in ROS generation. 24,26,43 This is related to …”

“…12,13 However, most of these agents are not cancerspecific, are very hydrophobic, and are not easy to formulate. 14 To overcome these barriers and provide additional PTT capability, several delivery systems, based on gold nanoparticles, gold nanorods, and graphene, have been reported.…”

Elsinochrome A photosensitizers: Alternative drugs for photodynamic therapy

“…For clinical application, an ideal phototherapeutic agent should exhibit a uniform composition, high quantum yield of reactive oxygen species (ROS), low dark toxicity, selective localization in diseased tissues, short metabolic period, etc. 11 Compared with extensively studied porphyrin-and phthalocyanine-like photosensitizers, perylenequinonoid photosensitizers almost have the above virtues of perfect photosensitizers. For instance, hypericin, a well-known perylenequinone, has been considered to be a promising agent for PDT of super¯cial cancers or as a photoactive antiviral agent.…”

Synthetic approaches to asymmetric phthalocyanines and their analogues

“…[1][2][3][4][5][6][7] Initially after their discovery, phthalocyanines were predominantly used as pigments and dyes in the textile and paper industries because of their chemical, photochemical, and thermal stabilities. 8,9 In more recent decades the chemistry of substituted phthalocyanines has undergone tremendous growth, [10][11][12] and, in addition to traditional applications, substituted and unsubstituted phthalocyanines have found potential applications in industrial catalysis, [13][14][15][16][17][18] photosensitizers for photodynamic cancer therapy, 16,[19][20][21][22][23][24][25][26] markers for bioimaging, 27,28 antibacterial composites, [29][30][31][32] materials for ink-jet printing, 33 chemical sensors, [34][35][36][37] semiconductors, 38,39 functional polymers and liquid crystals, [40][41][42][43] light-harvesting modules for dye-sensitized solar cells and organic photovoltaics, …”