An oxidizer-resistant fluorescence probe for detecting bisulfite and viscosity in biosystems

Abstract

Fluorescence probes bearing malononitrile derivatives as electron withdrawing group have attracted the interests of many researchers during the past decades. Even for the similar fluorophore, the sensing mechanism and pathway could be much different and hard to predict. Thus, we designed a fluorescence probe consisting 2-(3,5,5-trimethylcyclohex-2-en-1-ylidene)malononitrile as the electron withdrawing group and thienocoumarin as fluorophore in order to investigate the possible superiority in designing related optical sensors. In our research, it is interesting to find that our probe has the different properties compared with the similar reported probe bearing the coumarin fluorophore. The novel fluorescent probe (CSO–CN) was demonstrated to be able to detect HSO₃⁻ ions and changes in viscosity with a good resistance to oxidizers. The probe offers high sensitivity (LOD = 0.149 μM) for detecting HSO₃⁻ via the Michael addition reaction. It also enables fluorescence emission at 483 nm and the tracking of viscosity alternation by impeding the twisted intramolecular charge transfer (TICT) mechanism. Besides, the dual-functional probe has effectively been utilized to monitor HSO₃⁻ level in living cells, zebrafish and real food samples.