Synthesis and in vitro photodynamic activity of aza-BODIPY-based photosensitizers.

Aza-BODIPY dyes have recently come to attention owing to their excellent chemical and photophysical properties. In particular, their absorption and emission maxima can efficiently be shifted to the red or even to the NIR spectral region. On this basis, aza-BODIPY derivatives are widely investigated as fluorescent probes or phototherapeutic agents. Here we report the synthesis of a set of novel aza-BODIPY derivatives as potential photosensitizers for use in photodynamic therapy. Triazolyl derivatives were obtained via Cu(I)-catalyzed azide-alkyne cycloaddition as the key step. In vitro photodynamic activities of the newly synthesized compounds were evaluated on the A431 human epidermoid carcinoma cell line. Structural differences influenced the light-induced toxicity of the test compounds markedly. Compared to the initial tetraphenyl aza-BODIPY derivative, the compound bearing two hydrophilic triethylene glycol side chains showed substantial, more than 250-fold, photodynamic activity with no dark toxicity. Our newly synthesized aza-BODIPY derivative, acting in the nanomolar range, might serve as a promising candidate for the design of more active and selective photosensitizers.

Synthesis and estrogenic activity of BODIPY-labeled estradiol conjugates.

Novel BODIPY-estradiol conjugates have been synthesized by selecting position C-3-O for labeling. The conjugation strategy was based on Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) or etherification. Estradiol derivatives used as azide partners bearing an ω-azidoalkyl function through C4-C8-long linkers have been prepared. CuAAC reactions of estradiol azides with BODIPY alkyne furnished fluorescent 3-O-labeled conjugates bearing the triazole ring as a coupling moiety. Williamson etherifications of 3-O-(ω-bromoalkyl)-17ß-estradiol derivatives with BODIPY-OH resulted in labeled conjugates connected with an ether moiety. Interactions of the conjugates with estrogen receptor (ER) were investigated using molecular docking calculations in comparison with estradiol. The conjugates occupied both the classical and alternative binding sites on human ERα, with slightly lower binding affinity to references estradiol and diethystilbestrol. All compounds have displayed reasonable estrogenic activity. They increased the proliferation of ER-positive breast cancer cell line MCF7 contrary to ER-negative SKBR-3 cell line. The most potent compound 13a induced the transcriptional activity of ER in dose-dependent manner in dual luciferase recombinant reporter model and increased progesterone receptor's expression, proving the retained estrogenic activity. The fluorescence of candidate compound 13a co-localised with the ERα. The newly synthesized labeled compounds might serve as good starting point for further development of fluorescent probes for modern biological applications. In addition to studying steroid uptake and transport in cells, e.g. in the processes of biodegradation of estrogen-hormones micropollutants, they could also be utilized in examination of estrogen-binding proteins.