A carbazole-based mitochondria-targeted two-photon fluorescent probe for gold ions and its application in living cell imaging

摘要

A carbazole-based two-photon fluorescent probe (PyCM) showed a remarkable fluorescence "turn-on" response to Au~(3+)/Au~+ in aqueous solution with a large Stokes shift (119 nm). A good linear relationship of emission intensity at 539 nm against Au~(3+)/Au~+ from 0 to 20 equiv. was observed, and the detection limits (3σ/k) were as low as 47 nM for Au~(3+) and 73 nM for Au~+, respectively. The fluorescence enhancement was attributed to the gold ions-induced C=N bond hydrolysis sensing mechanism, which is fully confirmed by the UV-vis absorption, fluorescence, IR, ~1H NMR titration and MALDI-TOF mass analysis. Bio-imaging study established that PyCM could be used to detect Au~(3+) in living cells under two-photon excitation with large two-photon absorption cross sections (1321 GM at 860 nm), little cytotoxicity and good biocompatibility. Meanwhile, standard co-staining experiments of PyCM and MitoTracker Red FM (co-localization coefficient: 0.85) revealed that PyCM was predominantly present in mitochondria.