pH/glutathione dual-responsive magnetic carboxymethyl chitosan nanoparticles for the controlled release of astaxanthin

Astaxanthin (AST) bioavailability is inherently limited by poor stability. In this study, pH/glutathione (GSH) dual-responsive carboxymethyl chitosan (CMCS) superparamagnetic iron oxide (SPION) nanoparticles were prepared, loaded with AST (CMCS-SPION-AST), and characterized. Its stability, responsive release, and kinetics were studied. The results showed that CMCS-SPION successfully encapsulated AST. The composite showed excellent stability (88.66 % AST retention at 4 °C, light-protected) and the highest cumulative release (82.11 % at pH 5.5/10 mM GSH), which was higher than the release rates of previously reported single pH-responsive carriers. The release curves of CMCS-SPION-AST at pH 5.5, pH 7.4/10 mM GSH, and pH 5.5/10 mM GSH showed good model fit (R 2  > 0.9), indicating non-Fickian diffusion. The release process represents a synergistic effect of diffusion and dissolution. This study provides novel insight for the development of responsive drug delivery systems and expands the application prospects of AST as a functional natural pigment in the food industry.