ROS-responsive carboxymethyl chitosan nanoparticles loaded with astaxanthin for alleviating oxidative damage in intestinal cells.

The controlled release of antioxidant substances at the intestinal oxidative damage site is crucial for alleviating intestine-related diseases. Herein, the novel ROS-responsive carrier was synthesized through simple amidation reaction between carboxymethyl chitosan (CMC) and methionine (Met), a natural organic compound containing ROS-responsive linkages (thioether). Initially, astaxanthin (AXT) nanoparticles (AXT@CMT) with excellent stability and drug loading capacity (39.68 ± 0.23 μg/mL) were prepared by optimizing various reaction conditions. In the simulated high-concentration ROS environment of the intestine, CMT achieved a transition from hydrophobic groups (thioether) into hydrophilic groups (sulfone), which was conducive to the controlled release of AXT. In vitro cell experiments revealed that AXT@CMT could effectively alleviate the oxidative damage in intestinal epithelioid cell line No. 6 (IEC-6 cell) caused by HO. This study achieved a straightforward preparation of ROS-responsive nanocarrier through food ingredients, offering a theoretical foundation for the controlled release of AXT at the intestinal oxidative damage site.