The Use of Photodynamic Therapy in the Treatment of Endometrial Cancer-A Review of the Literature

Endometrial cancer is the most common malignant tumor of the female reproductive system. It develops in the mucous membrane lining the inside of the uterine body-the endometrium, through the abnormal and continuous growth of cancer cells originating from the uterine mucosa. In recent years, there has been a significant increase in the number of cases in European countries. Photodynamic therapy (PDT) is an innovative and dynamically developing medical procedure, useful in the treatment of cancer and non-cancer tissue conditions. The PDT reaction involves the activation of a photosensitizing substance with visible light, which in turn leads to the formation of free oxygen radicals, which contribute to the destruction of the cell. PDT is minimally invasive, has few side effects, and preserves organ anatomy and function. Both diagnostics and photodynamic therapy as modern methods of treatment are becoming more and more popular in many research units around the world. They are most often practiced and tested in in vitro experimental conditions. In clinical practice, the use of PDT is rare. Comprehensive cooperation between scientists contributes to taking steps towards obtaining new, synthetic photosensitizers, directing their physicochemical properties, and showing the impact on a given organism. This review examines the evidence for the potential and usefulness of PDT in the treatment of endometrial cancer. This review highlights that PDT is gaining popularity and is becoming a promising field of medical research.

Synthesis, Structure, and Redox and Optical Properties of 5,10,15,20-Tetraaryl-5-azaporphyrinium Salts

The fundamental properties of azaporphyrins can be modulated over a wide range by changing the number of meso-nitrogen atoms. Reported herein are the first examples of 5,10,15,20-tetraaryl-5-azaporphyrinium (MTAMAP) salts, which were prepared via metal-templated cyclization of the corresponding zinc(II) and copper(II) complexes of 10-aryl-1-chloro-19-benzoyl-5,15-dimesityl-10-azabiladiene-ac. The inclusion of one meso-nitrogen atom in the 5,10,15,20-tetraarylporphyrin skeleton considerably changes the redox and optical properties as well as the degree of aromaticity of the porphyrin ring. The present findings suggest that MTAMAP salts would be promising scaffolds for the development of new azaporphyrin-based ionic fluorophores and photosensitizers.

Easily Switchable 18π-, 19π-, and 20π-Conjugation of Diazaporphyrin Double-Pincer Bispalladium Complexes

Ni^II 3,7,13,17-tetrapyridyl-5,15-diazaporphyrin serves as a double tridentate ligand to Pd^II ions to provide a pincer-type bispalladium complex. Electrochemical analysis revealed that the bispalladium complex shows excellent ability to accept electrons and reversible redox properties due to the coordination of the two cationic Pd^II centers to the meso-nitrogen atoms. We isolated and characterized one- and two-electron reduction species of the bispalladium complex. The 20π antiaromatic nature of the two-electron reduction species was confirmed by ¹ H NMR spectroscopy, UV/Vis-near-IR (NIR) absorption spectra, and density functional theory (DFT) calculations. X-ray diffraction revealed highly twisted structures for the bispalladium complexes regardless of the oxidation state.

D-Mannose-appended 5,15-diazaporphyrin for photodynamic therapy

5,15-Diazaporphyrin appended with D-mannose moieties was prepared through Suzuki-Miyaura cross-coupling reaction and S_N2 alkylation. The resultant diazaporphyrin was hydrophilic enough to exhibit sufficient solubility in aqueous media. Because of the photosensitizing ability of diazaporphyrins, the in vitro activity of the D-mannose-appended diazaporphyrin in photodynamic therapy (PDT) was investigated. The specific internalization of the functionalized diazaporphyrin into human breast adenocarcinoma (MDA-MB-231) cells through mannose receptors was confirmed by confocal microscopy imaging. We also demonstrated the strong PDT activity of the functionalized diazaporphyrin at a nanomolar level with short light irradiation time.

Iron hexamesityl-5,15-diazaporphyrin: synthesis, structure and catalytic use for direct oxidation of sp3 C-H bonds

Iron hexamesityl-5,15-diazaporphyrin was synthesized through the cross-coupling reaction of tetrabromodiazaporphyrin. The use of chloroiron(iii) hexamesityl-5,15-diazaporphyrin as a catalyst for oxidation of cyclooctane showed high performance with a total TON up to 731. The introduction of bulky mesityl groups at β-positions prevented the catalyst deactivation via formation of a μ-oxo dimer.

Rational Synthesis of 5,10-Diazaporphyrins via Nucleophilic Substitution Reactions of α,α'-Dibromotripyrrin and Dihydrogenation to Give 5,10-Diazachlorins

We report here the first rational synthesis of 5,10-diazaporphyrins via nucleophilic substitution reactions of α,α'-dibromotripyrrin. Uses of 1,3-diiminoisoindoline and 3,4-di(ethylsulfanyl)pyrrole-2,5-diimine as nucleophiles allowed for synthesis of 5,10-diazabenzoporphyrin (2) and 5,10-diaza-7,8-di(ethylsulfanyl)porphyrin (3). 3 was reduced to 5,10-diazaporphyrin (4), 5,10-diaza-2,3-dihydrogenated porphyrin (5), and 5,10-diaza-7,8-dihydrogenated porphyrin (6) with yields that were dependent upon reduction conditions. All the structures of these products were confirmed by X-ray crystallographic analysis. Their optical and electrochemical properties have been comparatively studied with those of 5,15-diazaporphyrin (7) and 5,15-diazachlorin (8). Furthermore, NH tautomers of 2 and 4 were observed as different species in solution, and the dynamic NH tautomeric behavior was studied in 4.

Effects of the Peripheral Substituents, Central Metal, and Solvent on the Photochemical and Photophysical Properties of 5,15-Diazaporphyrins

Metal complexes of 3,7,13,17-tetrakis(di(4-carboxyphenyl)amino)-5,15-diazaporphyrin (MDAP-COOH; M=Pd, Cu) and their ethyl ester precursors (MDAP-COOEt; M=Pd, Cu) have been synthesized for use as near-infrared (NIR)-light-responsive photosensitizers. Under irradiation with visible or NIR light, PdDAP-COOEt in toluene generated singlet oxygen (¹ O₂ ) with an excellent quantum yield (Φ_Δ =0.99), whereas CuDAP-COOEt exhibited a lower efficiency (Φ_Δ =0.21). The water-soluble Pd^II complex PdDAP-COOH also behaved as a photosensitizer (Φ_Δ =0.20) in a micellar solution. The photophysical properties of these dyes were measured by transient absorption techniques. It was found that the efficiency of the energy transfer from the triplet state of MDAP-COOR (R=Et, H) to the ground state of dioxygen was highly dependent on the peripheral substituents, the central metal, and the solvent. Furthermore, the phototoxicity of PdDAP-COOH toward HeLa cells under irradiation of NIR light (720 nm) was evaluated. As expected, PdDAP-COOH exhibited good photodynamic activity, and control experiments confirmed that ¹ O₂ was generated as the active oxygen species.

Diazachlorin and diazabacteriochlorin for one- and two-photon photodynamic therapy

Diazachlorin and diazabacteriochlorin have been prepared through reduction of diazaporphyrin and their in vitro and in vivo activity in photodynamic therapy has been investigated.

Direct and Regioselective Amination of β-Unsubstituted 5,15-Diazaporphyrins with Amines: A Convenient Route to Near-Infrared-Responsive Diazaporphyrin Sensitizers

We have established a convenient method for the base-promoted direct amination of β-unsubstituted 5,15-diazaporphyrins (DAPs) with secondary and primary amines to produce 3,7,13,17-tetraamino- and 3-amino-DAPs, respectively, regioselectively. The amino groups attached at the periphery cause significant red shifts of the absorption bands as a result of their perturbation of the HOMO and/or LUMO in the DAP π-system. The palladium complex of a 3,7,13,17-tetrakis(diphenylamino)-DAP generated singlet oxygen in high yield under irradiation with near-infrared light.

Singlet oxygen generation properties of an inclusion complex of cyclic free-base porphyrin dimer and fullerene C60

We demonstrate that a cyclic free-base porphyrin dimer and its inclusion complex with fullerene C₆₀ possess the ability to generate singlet oxygen (¹O₂) under visible light irradiation.

Chemo- and Regioselective Reduction of 5,15-Diazaporphyrins Providing Antiaromatic Azaporphyrinoids

Reagent-controlled chemo- and regioselective reduction of 5,15-diazaporphyrins has been developed. The selective reduction of carbon-carbon double bonds of diazaporphyrins provides 18 π aromatic isobacteriochlorin-type products, whereas the reduction of carbon-nitrogen double bonds leads to selective formation of 20 π N,N'-dihydrodiazaporphyrins in excellent yields. The distinct antiaromatic character of N,N'-dihydrodiazaporphyrins has been revealed. The free-base N,N'-dihydrodiazaporphyrin exhibits slower inner NH tautomerism than that in the corresponding 18 π porphyrins.

Mitochondrial Reactive Oxygen Species and Photodynamic Therapy

Worldwide, the number of cancer cases is increasing. Typically, they are treated by either surgery or chemotherapy. However, these treatments may be undesirable in elderly patients or those who are under medication with antiplatelet drugs. Photodynamic therapy (PDT) represents a potentially attractive treatment option for these types of patients, since it does not involve surgery and has considerably reduced side effects compared to chemotherapy. Porphyrin, one of the most commonly used photosensitizers, has the convenient property of cancer-specific accumulation and therefore, is commonly used in PDT. However, the mechanism by which this cancer-specific accumulation occurs remains unclear. We previously reported that a heme-transport protein, HCP1, was capable of transporting porphyrin compounds. HCP1 expression is associated with increased hypoxia, although the detailed mechanism by which this regulation occurs is also unknown. Here, we review available data on the mechanism of regulation of HCP1 expression through mitochondrial reactive oxygen species (mitROS). Specifically, cancer cells show increased expression of HCP1 compared to normal cells and this over-expression is reduced in cancer cells over-expressing the mitROS scavenging enzyme manganese superoxide dismutase (MnSOD). Thus we conclude that mitROS is involved in regulating HCP1 expression.

Comparison of electronic effects of β-aryl substituents on optical and electrochemical properties of 5,15-diazaporphyrin π-systems

The syntheses and optical/electrochemical properties of 3-aryl-10,20-dimesityl-5,15-diazaporphyrin-metal complexes (MDAPs; mesityl = 2,4,6-trimethylphenyl; M = Ni , Zn ) are reported. Treatment of 3-bromo-MDAPs with arylboronic acids in the presence of a Pd catalyst and a bulky phosphine ligand in a dioxane-water mixed solvent afforded the corresponding 3-aryl-MDAPs in moderate to good yields. X-ray crystallographic analysis of p- EtO 2 CC 6 H 4- NiDAP showed that the β-aryl group was tilted toward the NiDAP ring, with a dihedral angle of 21.7°. In the UV-visible absorption spectra, all the Ar-MDAPs showed intense Q-bands attributable to HOMO-to-LUMO transitions. The para substituents were found to influence the HOMO energies, which eventually resulted in fine tuning of the HOMO–LUMO gaps of the diazaporphyrin chromophores. It is worth noting that the p- Ph 2 NC 6 H 4- ZnDAP showed broad absorption and emission bands in the visible-near-infrared regions. The large Stokes shifts and their linear solvation energy relationships vs. orientation polarizability show that this Ph 2 N -substituted derivative has intrinsically high charge transfer from the triphenylamine (donor) to the ZnDAP (acceptor) unit. These experimental observations were supported by theoretical calculations for model Ar-ZnDAP compounds. These results confirm that the introduction of a highly electron-donating aryl group at the peripheral β-carbon is a promising strategy for enhancing the light-harvesting and light-emitting abilities of diazaporphyrin-based π-systems in the visible-near-infrared regions.