Structural and photophysical evaluation of O-alkoxy-substituted BODIPY dyes in liposomes.

To visualize and deeply understand biochemical structures and functionalities, bright and easily synthesizable probes for bioimaging readouts are required. Hence, the visualization of cellular membranes is key due to their biological role. In this work, six rationally designed alkoxy-substituted 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) fluorophores were synthesized and investigated. With this design, we aimed to evaluate how the presence of structurally different short ethylene glycol subunits in the para-position of meso-phenyl-substituted BODIPY impacts the overall molecular hydrophilic/hydrophobic balance, the related optical properties, and the staining of lipid bilayer membranes in large unilamellar vesicles (LUVs) as cell membrane models. The photophysical properties were deeply studied with respect to the probe structure, and we obtained versatile key data to support the design of new fluorescent sensors for biological applications.