Photophysical, photooxidation, and biomolecule-interaction of meso-tetra(thienyl)porphyrins containing peripheral Pt(II) and Pd(II) complexes. Insights for photodynamic therapy applications.

We report the synthesis and characterization of two novel tetra-cationic porphyrins, containing Pt(II) or Pd(II) polypyridyl complexes attached at the peripheral position of N4-macrocycle. Compounds were characterized through elemental analysis, molar conductivity, cyclic voltammetry, and spectroscopy analysis. Photophysical and photobiological parameters were also evaluated. Also, the binding capacity of each porphyrin with human serum albumin (HSA) was determined by UV-Vis, steady-state, and time-resolved fluorescence spectroscopy, combined with molecular docking calculations. The results suggest that the interaction of these compounds is spontaneous, weak to moderate, and probably occurs at site III (subdomain IB) by non-covalent forces, including van der Waals and H-bonding. Moreover, porphyrins containing peripheral complexes improve their interactions with biomolecules, show good photostability, generate reactive oxygen species under white light studied by electron paramagnetic resonance (EPR) analysis, and promote photo-damage of HSA.

Photodynamic therapy with a new bacteriochlorin derivative: Characterization and in vitro studies.

Photodynamic therapy presents a therapeutic choice that can be utilized to treat diverse neoplasms. In this technique, the critical element is a photosensitive molecule that absorbs light energy and transfers it to molecular oxygen or biological molecules to form reactive oxygen species, thus inducing irreversible damage to target cells and ultimately leading to cell death. Bacteriochlorin derivatives are employed as photosensitizers (PSs), possessing light-absorbing capacity in the near-infrared region. The objective of this study was to prepare a semi-synthetic bacteriochlorin from Rhodopseudomonas faecalis and adding Trizma® to improve solubility. Cell viability tests, flow cytometry (apoptotic and necrotic cells were identified by Annexin V and propidium iodide), and confocal microscopy were used to evaluate the photoactivity of bacteriochlorin-Trizma (Bchl-T) in fibroblast (HFF-1-control cells) and breast cancer (MCF-7 cells-target cells) cells. At concentrations above 0.5 µM, Bchl-T demonstrated 80 % cell death, presenting the highest PS interaction (via fluorescence microscopy) with lysosomes, mitochondria, and the endoplasmic reticulum; the cell death type was revealed as apoptosis (via cytometry). Our findings indicated the suitability of Bchl-T for future application in photodynamic therapy against cancer cells by inducing apoptosis.