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 %).