Substituted Tetraphenylvinylethylene (TPE) Small Molecular Luminescence Probes Showing Stimuli-Responsive Emission Properties and Tunable Cellular Imaging.

Aggregation-induced emission (AIE) has enabled the development of organic luminogens with enhanced emission in the aggregated state, offering significant potential for bioimaging applications. Herein, we report a series of tetraphenylethylene (TPE)-based small-molecule AIE probes for targeted cellular imaging. Four luminogens were rationally designed by functionalizing the TPE core with acid, ester, oxime, and ketal groups, affording TPE-Acid, TPE-Ester, TPE-Oxime, and TPE-Ketal. All compounds exhibit pronounced AIE characteristics, showing strong fluorescence in water-rich media and distinct stimuli-responsive emission behavior. Photophysical and theoretical studies reveal that emission properties can be effectively tuned through substituent variation. In vitro cytotoxicity assays using N2a (mouse neuroblastoma) cells confirm excellent biocompatibility. Live-cell imaging demonstrates that TPE-Acid and TPE-Ester produce strong intracellular fluorescence under violet excitation, whereas TPE-Oxime and TPE-Ketal emit efficiently under UV excitation. These findings highlight the effectiveness of substituent engineering on the TPE scaffold for modulating emission behavior and developing versatile AIE-active probes for biological imaging.