Novel BODIPY Dyes with a Meso-Benzoxadiazole Substituent: Synthesis, Photophysical Studies, and Cytotoxic Activity Under Normoxic and Hypoxic Conditions

Background/Objectives: Novel boron dipyrromethene derivatives with a heterocyclic, benzoxadiazole substituent were obtained as potential candidates for the photodynamic therapy (PDT) of cancers. Photochemical properties (e.g., singlet oxygen generation quantum yields (ΦΔ), absorption, and emission spectra) and cytotoxic activity studies in normoxic and hypoxic conditions were performed to verify the potential of novel BODIPYs as photosensitizers for PDT. Methods: Obtained dyes were characterized using mass spectrometry and various NMR techniques. The relative method with Rose Bengal as a reference and 1,3-diphenylisobenzofuran as a singlet oxygen quencher was used to determine ΦΔ values. The in vitro studies were conducted on human ovarian carcinoma (A2780) and human breast adenocarcinoma (MDA-MB-231) cells. Results: Photochemical studies showed that the presence of benzoxadiazole moiety only slightly affected the localization of the absorption maxima but resulted in fluorescence quenching compared with meso-phenyl-substituted analogs. In addition, brominated and iodinated analogs revealed a high ability to generate singlet oxygen. Anticancer studies showed high light-induced cytotoxicity of BODIPYs containing heavy atoms with very low IC50 values in the 3.5-10.3 nM range. Further experiments revealed that both compounds also demonstrated phototoxic activity under hypoxic conditions. The most potent cytotoxic effect in these conditions was observed in the iodinated BODIPY analog with IC50 values of about 0.3 and 0.4 μM for A2780 and MDA-MB-231 cells, respectively. Conclusions: The results of this study highlighted the advantages and some potential drawbacks of BODIPY compounds with heavy atoms and benzoxadiazole moiety as a useful scaffold in medicinal chemistry for designing new photosensitizers.

Liposomal Formulations of Novel BODIPY Dimers as Promising Photosensitizers for Antibacterial and Anticancer Treatment

Synthesis, photochemical properties, liposomal encapsulation, and in vitro photodynamic activity studies of novel BODIPY dimer connected at meso-meso positions and its brominated and iodinated analogs were described. UV-Vis measurements indicated that the dimeric structure of obtained BODIPYs did not significantly influence the positions of the absorption maxima. Emission properties and singlet oxygen generation studies revealed a strong heavy atom effect of brominated and iodinated BODIPY dimers, manifested by fluorescence intensity reduction and increased singlet oxygen generation ability compared to analog without halogen atoms. For the in vitro photodynamic activity studies, dimers were incorporated into two different types of liposomes: positively charged DOTAP:POPC and negatively charged POPG:POPC. The photoinactivation studies revealed high activity of brominated and iodinated dimers incorporated into DOTAP:POPC liposomes on both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. Anticancer studies on human breast adenocarcinoma MDA-MB-231 and human ovarian carcinoma A2780 cells revealed that DOTAP:POPC liposomes containing brominated and iodinated dimers were active even at low nanomolar concentrations. In addition, they were more active against MDA-MB-231 cells than A2780 cells, which is particularly important since the MDA-MB-231 cell line represents triple-negative breast cancer, which has limited therapeutic options.

Microwave-assisted synthesis, photochemical and electrochemical studies of long-wavelength BODIPY dyes

Novel BODIPY derivatives possessing different styryl substituents were synthesized using different methods of Knoevenagel-type condensation with conventional heating and microwave radiation in two conditions. Microwave-assisted synthesis significantly reduces reaction time while enhancing its efficiency. The introduction of styryl substituents at the 3 and 5 positions of the BODIPY core resulted in a substantial bathochromic shift, which was affected by the substituents within styryl groups. Depending on the solvents, the BODIPY with unsubstituted styryl groups possesses absorption maxima (λAbs) between 616 and 626 nm. While the analogs containing electron-donating methoxy and methylthio groups exhibited bathochromically shifted bands with λAbs values in the 633-654 nm range. Fluorescence studies revealed intensive emission of tested BODIPYs with fluorescence quantum yields at the 0.41-0.83 range. On the other hand, singlet oxygen quantum yields were very low. In the electrochemical studies, the CV and DPV scans showed the presence of three redox processes. The calculated electrochemical gaps were in the range of 1.71-1.87 V.

Porphyrinoids in photodynamic diagnosis and therapy of oral diseases

Photodynamic methods have found application not only in the treatment process as photodynamic therapy but also for the early detection of neoplastic lesions and tumors as photodynamic diagnosis. Early detection of the disease allows not only to avoid the patient’s lifetime risk but also significantly reduce the costs of anticancer therapy, which are increasing every year. There is a constant search for new and more effective photosensitizers which will provide safety in therapy while maintaining efficiency. This paper summarizes recent reports focused on the photodynamic diagnosis of oral cancers. Moreover, it shows methods of the photodynamic treatment of oral verrucous hyperplasia, erythroleukoplakia, and oral leukoplakia. The treatment of choice for these diseases is a surgical excision, which always leads to scar formation. Photodynamic therapy provides a new scar-less tool for the treatment.