Point-of-Care and Dual-Response Detection of Hydrazine/Hypochlorite-Based on a Smart Hydrogel Sensor and Applications in Information Security and Bioimaging

A novel dual-response fluorescence probe (XBT-CN) was developed by using a fluorescence priming strategy for quantitative monitoring and visualization of hydrazine (N₂H₄) and hypochlorite (ClO^-). With the addition of N₂H₄/ClO^-, the cleavage reaction of C=C bond initiated by N₂H₄/ClO^- was transformed into corresponding hydrazone and aldehyde derivatives, inducing the probe XBT-CN appeared a fluorescence "off-on" response, which was verified by DFT calculation. HRMS spectra were also conducted to confirm the sensitive mechanism of XBT-CN to N₂H₄ and ClO^-. The probe XBT-CN had an obvious fluorescence response to N₂H₄ and ClO^-, which caused a significant color change in unprotected eyes. In addition, the detection limits of XBT-CN for N₂H₄ and ClO^- were 27 nM and 34 nM, respectively. Interference tests showed that other competitive analytes could hardly interfere with the detection of N₂H₄ and ClO^- in a complex environment. In order to realize the point-of-care detection of N₂H₄ and ClO^-, an XBT-CN@hydrogel test kit combined with a portable smartphone was developed. Furthermore, the portable test kit has been applied to the detection of N₂H₄ and ClO^- in a real-world environment and food samples, and a series of good results have been achieved. Attractively, we demonstrated that XBT-CN@hydrogel was successfully applied as an encryption ink in the field of information security. Finally, the probe can also be used to monitor and distinguish N₂H₄ and ClO^- in living cells, exhibiting excellent biocompatibility and low cytotoxicity.