A chitosan-based near-infrared ratiometric fluorescent nanoprobe created by molecular assembly with applications in hypochlorous acid detection in live mouse

Hypochlorous acid (HClO/ClO^-) is a key reactive oxidative species (ROS) in the body. The HClO/ClO^- concentrations are imbalanced during cancer formation due to the ROS stress response. This paper introduces a novel chitosan-based self-calibration fluorescent nanoprobe (ChCyNil) constructed by molecular assembly for the ratiometric detection of HClO/ClO^-. Two chromophores with different fluorescence characteristics and HClO/ClO^- sensitivity were labeled on chitosan, and nanoparticles were prepared by a self-assembly strategy for HClO/ClO^- detection. ChCyNil exhibits several advantages, such as dual near-infrared emissions at 670 nm and 845 nm, tunable fluorescence intensity, self-calibration fluorescence, and good biocompatibility, improving its accuracy in HClO/ClO^- detection. Our study confirmed that ChCyNil exhibits a well-assembled spheroidal nanostructure and good photophysical properties in solution. The fluorescence imaging properties were further proved by detecting endogenous HClO/ClO^- produced by LPS/PMA stimuli in cells and zebrafish. In addition, ChCyNil was used to detect the fluorescence behavior of HClO/ClO^- in tumors of live mice. The successful design and fabrication of ChCyNil have presented a new strategy for constructing detection tools with improved fluorescence properties for HClO/ClO^- in live animals.