Labeling selectivity of lipid droplets fluorescent probes: Twisted intramolecular charge transfer (TICT) vs intramolecular charge transfer (ICT)

Fluorescence imaging technology is a versatile and essential tool in the field of biomedical research. To obtain excellent imaging results, the precise labeling of fluorescent probes is an important prerequisite. Nevertheless, the labeling selectivity of most fluorescent probes is not satisfactory, new design concepts are desperately needed. In this context, two isomeric lipid droplets (LDs) fluorescent probes Lipi-Cz-1 and Lipi-Cz-2 have been sophisticatedly developed with TICT and ICT-emitting characteristic, respectively. The more environmentally sensitive TICT-emitting Lipi-Cz-1 exhibits a significantly enhanced labeling selectivity in LDs imaging compared to the ICT-emitting Lipi-Cz-2, sufficiently illustrating the effectiveness of TICT-emitting characteristic in improving labeling selectivity. Additionally, Lipi-Cz-1 displays high photostability and biocompatibility. These advantages enable Lipi-Cz-1 to be finely applied in multimode fluorescence imaging, e.g. time-lapse 3D confocal imaging to monitor changes of the number and size of LDs during starvation, two-photon 3D imaging to compare the variations of LDs in various liver tissues, and STED super-resolution imaging to visualize the nanoscale LDs with the resolution of 65 nm. Overall, these imaging findings validate the effectiveness of the new strategy for improving the labeling selectivity.