A diarylethene-based probe with HSO3--activated fluorescence to photochromism: Its imaging application in living cells and zebrafish.

Sulfur dioxide (SO2) and its derivatives (sulfite SO32- and bisulfite HSO3-) have important applications in industrial production and food preservation, but excessive intake can be hazardous to human health. Therefore, the development of highly sensitive and selective HSO3- detection methods is essential to safeguard food safety and public health. Conventional HSO3- probes mainly rely on colorimetric or fluorescence detection, but these methods have obvious limitations in that the fluorescence signal disappears as soon as the UV irradiation is stopped, and they cannot provide long-lasting and readable detection results. Herein, a fluorescent probe (DP-1) constructed from diarylethene, fluorophores and ion recognition sites were designed and developed. DP-1 emits yellow fluorescence emission maximum at 600 nm in initial state, which is significantly quenched upon specific recognition of HSO3-. This recognition process demonstrates DP-1's good ion selectivity, interference resistance, and low detection limit of 16 nM. Notably, unlike conventional probes, DP-1 exhibits superior fluorescence properties before recognizing HSO3-, with no detectable photochromism. After ion recognition, its photochromic function is activated, while fluorescence completely disappears, demonstrating a switch from fluorescence to photochromism triggered by HSO3-. The mechanism of this recognition process was confirmed by nuclear magnetic titration, high-resolution mass spectrometry, and theoretical calculations. Additionally, DP-1 has been successfully applied for HSO3- detection in both live cellular and zebrafish imaging, with its excellent biocompatibility providing a reliable tool for in vivo imaging.