Discovery of asymmetric pyridinium-based fluorescent probes with large Stokes shifts for live neural stem/progenitor cells

Abstract

Fluorescent dyes are widely used in biological systems, yet the number of fluorescent scaffolds with desirable photophysical properties remains limited. Herein, we report the synthesis of novel asymmetric pyridinium salts via facile Rh(III) C-H activation, designed to exhibit biological activity in live cells. Interestingly, a structure–activity relationship (SAR) study revealed a key structural element in pyridinium salts, leading to the identification of the candidate compound as 1-([1,1'-biphenyl]-4-yl)-2-cyclopentyl-3-(4-(dimethylamino)phenyl)-5-methylpyridin-1-ium tetrafluoroborate (KD01), which showed a fluorescence having a large Stroke shift (excitation/emission = 405/605 nm) only when it was exposured to a live brain cells. Remarkably, it selectively labels undifferentiated neural stem/progenitor cells in humans while showing minimal interaction with differentiated neural cells. This work presents a bioactive fluorescent scaffold with unique optical properties and stem/progenitor cell selectivity, offering a promising platform for live-cell imaging and targeted neural cell identification.