Comprehensive Physicochemical Characterization and Release Kinetics of an Astaxanthin Nanoplex: Integrated In Silico and In Vitro Evaluation

Abstract

Abstract

Astaxanthin (AST) is a potent xanthophyll carotenoid that is well known for its extraordinary therapeutic and antioxidant properties. However, its weak water solubility and low bioavailability limit its application in pharmaceuticals. The present study aimed to enhance the solubility, stability, and sustained release of AST by developing an AST–chitosan (AST–CHT) nanoplex via green polyelectrolyte complexation. The nanoplex was lyophilized to obtain a stable dry powder and systematically characterized for its physicochemical properties. Comprehensive evaluations, including particle size analysis, entrapment efficiency, zeta potential, Fourier-transform infrared spectroscopy, powder X-ray diffraction, differential scanning calorimetry, and transmission electron microscopy, confirmed successful nanoplex formation with improved solubility and amorphous transformation. Molecular docking studies revealed stable electrostatic and hydrophobic interactions between AST and CHT, thereby supporting the complex’s stability. The optimized formulation, F5 (AST:CHT = 1.48:1% w/w), was selected based on its high entrapment efficiency (71.8%), appropriate particle size (420.1 nm, polydispersity index of 0.465), drug loading (0.79), and moderate zeta potential (−12.87 mV), which together ensured optimal stability and sustained release performance. In vitro release studies indicated sustained release following zero-order and Korsmeyer–Peppas kinetics (correlation coefficient of 0.9759). Stability analysis confirmed stability for 2 months. Overall, the developed AST–CHT nanoplex offers a promising, eco-friendly, and mechanistically supported nanodelivery system for improving the therapeutic performance and bioavailability of AST.