Unsymmetrical Mesoporphyrinic Complexes of Copper (II) and Zinc (II). Microwave-Assisted Synthesis, Spectral Characterization and Cytotoxicity Evaluation

Porphyrin Macrocycles: General Properties and Theranostic Potential

Despite specialists' efforts to find the best solutions for cancer diagnosis and therapy, this pathology remains the biggest health threat in the world. Global statistics concerning deaths associated with cancer are alarming; therefore, it is necessary to intensify interdisciplinary research in order to identify efficient strategies for cancer diagnosis and therapy, by using new molecules with optimal therapeutic potential and minimal adverse effects. This review focuses on studies of porphyrin macrocycles with regard to their structural and spectral profiles relevant to their applicability in efficient cancer diagnosis and therapy. Furthermore, we present a critical overview of the main commercial formulations, followed by short descriptions of some strategies approached in the development of third-generation photosensitizers.

Main Strategies for the Synthesis of meso-Arylporphyrins

meso-Arylporphyrins as most accessible tetrapyrrole macroheterocycles have always been the focus of attention from researchers concerned with practically useful properties of these compounds. The first syn­theses of meso-arylporphyrins date back to about 90 years ago. Up to now, the yields of these compounds have been improved from 5 to 80%. The present review analyzes different ways and strategies for the synthesis of meso-aryl-substituted porphyrins. The most efficient methods that can be scaled up to an industrial level have been identified.

Developing a Novel Nanoscale Porphyrinic Metal-Organic Framework: A Bifunctional Platform with Sensitive Fluorescent Detection and Elimination of Nitenpyram in Agricultural Environment

Developing a rapid sensing platform with effective pesticide degradation capabilities integrated into a single structure and realistic application is an imminent challenge to ensure sustainable agriculture and food safety. Here, we described establishment of a bifunctional nanoscale porphyrinic metal-organic framework (MOF) probe serving as a sensor for detection of trace nitenpyram and as a photocatalyst to facilitate the pesticide degradation. Based on the signal turned "on-off", the strong fluorescence of the probe was quenched by the target, leading to the sensing range from 0.05 to 10.0 μg mL^-1 and a detection limit of 0.03 μg mL^-1. Given the versatile design by which the porphyrin photosensitizers were isolated subtly in the MOF to avoid self-quenching, the probe was endowed with sustainable and efficient pesticide photodegradation activity with a degradation rate of ∼95% for nitenpyram. Our work represents powerful all-in-one MOF-derived materials jointly for sensing and degrading pesticide residues in agricultural soils and other pesticide-contaminated environments.

Studies on the Synthesis, Photophysical and Biological Evaluation of Some Unsymmetrical Meso-Tetrasubstituted Phenyl Porphyrins

We designed three unsymmetrical meso-tetrasubstituted phenyl porphyrins for further development as theranostic agents for cancer photodynamic therapy (PDT): 5-(4-hydroxy-3-methoxyphenyl)-10,15,20-tris-(4-acetoxy-3-methoxyphenyl)porphyrin (P2.2), Zn(II)-5-(4-hydroxy-3-methoxyphenyl)-10,15,20-tris-(4-acetoxy-3-methoxyphenyl)porphyrin (Zn(II)2.2) and Cu(II)-5-(4-hydroxy-3-methoxyphenyl)-10,15,20-tris-(4-acetoxy-3-methoxyphenyl)porphyrin (Cu(II)2.2). The porphyrinic compounds were synthesized and their structures were confirmed by elemental analysis, FT-IR, UV-Vis, EPR and NMR. The compounds had a good solubility in polar/nonpolar media. P2.2 and, to a lesser extent, Zn(II)2.2 were fluorescent, albeit with low fluoresence quantum yields. P2.2 and Zn(II)2.2 exhibited PDT-acceptable values of singlet oxygen generation. A “dark” cytotoxicity study was performed using cells that are relevant for the tumor niche (HT-29 colon carcinoma cells and L929 fibroblasts) and for blood (peripheral mononuclear cells). Cellular uptake of fluorescent compounds, cell viability/proliferation and death were evaluated. P2.2 was highlighted as a promising theranostic agent for PDT in solid tumors considering that P2.2 generated PDT-acceptable singlet oxygen yields, accumulated into tumor cells and less in blood cells, exhibited good fluorescence within cells for imagistic detection, and had no significant cytotoxicity in vitro against tumor and normal cells. Complexing of P2.2 with Zn(II) or Cu(II) altered several of its PDT-relevant properties. These are consistent arguments for further developing P2.2 in animal models of solid tumors for in vivo PDT.

Synthesis, Spectral Analysis and Preliminary in Vitro Evaluation of Some Tetrapyrrolic Complexes with 3d Metal Ions

In this paper, two tetrapyrrolic complexes, Zn(II)-5-(3-hydroxyphenyl)-10,15,20-tris-(4-acetoxy-3-methoxyphenyl)porphyrin and Cu(II)-5-(3-hydroxyphenyl)-10,15,20-tris-(4-acetoxy-3-methoxyphenyl)porphyrin were synthesized, and characterized from a spectral and biological point of view. The study provided data concerning the behavior of identical external substituents vs. two different core insertions. Some of the properties of the proposed tetrapyrrolic structures were highlighted, having photodynamic therapy of cancer as a targeted biomedical application. Elemental analysis, NMR, FTIR and UV-Vis data in various solvents were provided. A preliminary in vitro study on normal and cancer cultured cells was carried out for biocompatibility assessment in dark conditions. The preliminary in vitro study performed on human peripheral mononuclear cells exposed to tetrapyrrolic compounds (2 µM) showed that the proposed compounds had a convenient cytotoxic profile on human normal peripheral blood mononuclear cells under dark conditions. Meanwhile, the investigated compounds reduced the number of metabolically active breast tumor MCF-7 cells, with the exception of Zn(II) complex-containing a symmetrical ligand. Accordingly, preliminary in vitro data suggest that the proposed tetrapyrrolic compounds are good candidates for PDT, as they limit tumor expansion even under dark conditions, whilst sparing normal cells.

Microwave synthesis under solvent-free conditions and spectral studies of some mesoporphyrinic complexes

A series of A₃B and A₄ type mesoporphyrinic complexes were synthesized with superior yields using microwave irradiation under solvent-free conditions. The structures of the complexes were confirmed using elemental analysis, FT-IR, UV-Vis, EPR and NMR spectral data. The influence of environmental polarity on spectral properties of the mesoporphyrinic complexes was investigated. The obtained results indicate that the shape of absorption and fluorescence spectra does not depend on the solvent polarity under the experimental conditions used. The small shifts of the absorption and emission maximums that occur by increasing of solvent polarity reflects the physical interaction between the porphyrinic substituents and the solvent molecules.

Spectroscopic behavior of some A(3)B type tetrapyrrolic complexes in several organic solvents and micellar media

The paper presents spectral studies of some unsymmetrical A₃B tetrapyrrolic, porphyrin-type complexes with Cu(II) and Zn(II) in different solvents and micellar media aimed at estimating their properties in connection with the living cell. The results indicate that the position of the absorption and emission peaks is mostly influenced by the central metal ion and less by the environmental polarity or the peripheric substituents of the porphyrinic core. The comparison between the overall absorption and emission spectra of the compounds in methanol or cyclohexane vs. direct and reverse Triton X micellar systems, respectively, suggests for all compounds the localization at the interface between the polyethylene oxide chains and the tert-octyl-phenyl etheric residue of the Triton X-100 molecules. These findings could be important when testing the compounds embedded in liposomes or other delivery systems to the targeted cell.