Water-soluble small-molecule probes for RNA based on a two-photon fluorescence “off–on” process: systematic analysis in live cell imaging and understanding of structure–activity relationships

Abstract

The conveniently obtained water-soluble small-molecule L1–5 were selective for RNA with remarkable “off–on” two-photon fluorescence responses in vitro and in vivo, showing that L1–5 can surprisingly stain mitochondria or nucleoli individually with orange fluorescence under different focal lengths. Compounds L6–8 were prepared, for comparison, to further explore the mechanism of the binding of L1–5 with RNA, which revealed that the synergistic effect of the amino group and the pyridinium cation played a significant role in distinct cell imaging.