A biocompatible chitosan-based fluorescent polymer for efficient H₂O₂ detection in living cells and water samples

As a biomarker of oxidative stress, hydrogen peroxide (H₂O₂) plays a complex role in organisms, including regulating cell signaling, respiration, the immune system, and other life processes. Therefore, it is important to develop a tool that can simply and effectively monitor H₂O₂ levels in organisms and the environment. In this work, naphthalene fluorophores with a borate structure were introduced into chitosan (CTS) azide, and a CTS-based fluorescence sensor (CTS-HP) was designed for sensitive H₂O₂ detection. The biocompatibility and degradability of CTS endowed CTS-HP with reduced biotoxicity compared with organic fluorescent dyes, and the substitution degree of fluorophores on the CTS chains was 0.703. The randomly coiled chain structure of the CTS-HP probe enabled the boronic acid recognition sites on the fluorophores to achieve the enrichment of analyte H₂O₂ through a synergistic effect. Therefore, the probe CTS-HP (10 μg mL^-1) exhibited a 21-fold fluorescence enhancement and good detection limit (LOD = 8.98 nM) in H₂O₂ solution, reaching the maximum fluorescence response faster (within 16 min). The probe also successfully achieved the fluorescence imaging of endogenous and exogenous H₂O₂ in zebrafish and living cells and labeled the recovery experiment of H₂O₂ in real water samples (recoveries rates of 90.93-102.9 % and RSD < 3.09 %).