A Dicyanoisophorone‐Naphthalimide‐Based Ratiometric Fluorescent Probe for the Detection of Cysteine and Its Applications

Cysteine (Cys) plays an essential role in both food processing and physiological functions; however, excessive intake may pose potential health risks. In this work, a novel ratiometric fluorescent probe DCI-NI-Cys, based on naphthalimide-dicyanoisophorone hybrid, was synthesized for detecting Cys. In the design of the probe, the acrylate group was used as the reaction site for Cys. The probe demonstrated remarkable selectivity and high sensitivity toward Cys detection. Specifically, the limit of detection was determined to be 93 nM in fluorescence spectra and 118 nM in UV-vis absorption spectra, respectively. Moreover, a smartphone-based sensing platform was successfully developed by coupling the probe with RGB color analysis software. DCI-NI-Cys proved capable of detecting Cys in food samples such as cabbage, pear, garlic, and celery with satisfactory recoveries, underscoring its potential for real-world applications. Impressively, DCI-NI-Cys is applicable to image Cys in HepG2 cells and zebrafish.