Two-photon fluorescence imaging of RNA in nucleoli and cytoplasm in living cells based on low molecular weight probes

•Two low molecular weight ribonucleic acid probes were designed and synthesized.•Both displayed better photostability than the commercially available probe.•Both possessed large two-photon fluorescence action absorption cross-sections.•Both can achieve one- and two-photon image of ribonucleic acid in living cells.

Two low molecular weight, indole-based, mono-cationic probes, were designed and synthesized. According to their spectral response to ribonucleic acid in vitro and direct fluorescence imaging in living cell lines, the two compounds were identified as ribonucleic acid-selective fluorescent turn-on probes with large two-photon excited fluorescence action absorption cross-sections when binding to ribonucleic acid. Moreover, both dyes with good membrane permeability have been successfully used to image ribonucleic acid in nucleoli and cytoplasm in living cells by confocal and two-photon fluorescence microscopy. Furthermore, the dyes possess good counterstain compatibility with Hoechst 33342, important deoxyribonucleic acid-staining dyes for ribonucleic acid–deoxyribonucleic acid colocalization.

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