Synthesis of Aza-BODIPYs, Their Differential Binding for Cu(II), and Results of Bioimaging as Fluorescent Dyes of Langerhans β-Cells

Cellular labeling through the use of dyes is of great interest to the biomedical sciences for the characterization of the location and distribution of biomolecules and also for the tracking of the course of biological processes in both health and illness. This paper reports the synthesis, characterization, and subsequent evaluation as metal sensors and cell staining probes of four aza-BODIPY compounds [herein referred to as 7(a-d)]. Compounds 7(b-d) were found to display an outstanding selectivity for Cu(II) because their emission band at 720 nm was progressively quenched by this metal, presenting fluorescence quenching between 75 and 95%. On the other hand, cell imaging studies with pancreatic β-cells proved that aza-BODIPYs 7a and 7b showed selectivity for the cytoplasm, while 7c and 7d were selective for the cell membrane. Moreover, aza-BODIPY 7b allowed to characterize in a clear way a lipotoxic condition mediated by saturated fatty acids, a critical phenomenon on β-cell damage associated with diabetes mellitus type II. Taken together, the presented results highlight the obtained aza-BODIPY compounds as selective sensing/staining probes with the potential to be used in the biomedical field.