Development of a semiacenaphthenofluorescein-based optical and fluorescent sensor for imaging cysteine in cells

A novel chromogenic and fluorescent sensor based on semiacenaphthenofluorescein (Probe 1) was designed and synthesized. This probe exhibited superior selectivity and sensitivity for cysteine (Cys) over other analogues, such as homocysteine and glutathione, and the corresponding detection limit was 0.086 μM, which was much lower than intracellular concentration. The tandem conjugate addition/cyclization sequence mechanism was revealed by mass spectrometry, 1H NMR examination and density functional theory (DFT) calculations. Finally, the results of photostability, cell imaging and viability assays showed that the probe possessed excellent membrane permeability, hypotoxicity and fluorescent imaging of cysteine, which indicated its potential applications in living cells.