Red turn-on fluorescent phenazine-cyanine chemodosimeters for cyanide anion in aqueous solution and its application for cell imaging

摘要

Two chemodosimeters PDMI and PMI for cyanide detection were designed and synthesized based on phenazine-cyanine dyes with N-methyl indolium group as receptor unit. According to the specific reactivity of indolium C=N~+ bond against cyanide anion, both of them featured high sensitivity with detection limit of 1.4 μM and 200 nM, respectively, and high selectivity against other anions. The quenching effect on phenazine-cyanine fluorophore by strong intramolecular charge transfer (ICT) from phenazine donor to indolium receptor made both PDMI and PMI non-emissive at the original state. After addition of cyanide, the ICT effect decreased and vanished leading to dramatic "off-on" fluorescence enhancement. PDMI which proceeded bilateral electrophilic reaction toward cyanide anion provided an emission signal at 580 nm in HEPES buffer with naked-eye detectable color change. Probe PMI utilized an unreactive formyl group instead of one reactive N-methyl indolium group as the electron-withdrawing component. Due to the unilateral recognition process for cyanide the ICT orientation of PMI was redirected thus exhibited fluorescence enhancement with maximum emission at 630 nm. Meanwhile, PMI was applied for monitoring intracellular cyanide in Hela cells and proved to achieve "off-on" fluorescent signal confirmed by confocal laser scanning microscopic imaging.