Tuning the Network Structure of Crosslinked Chitosan Nanocarriers for Sustained Release of Divalent Micronutrients

ABSTRACT

Biopolymer‐based nanocarriers have become promising systems for sustained ion delivery due to the tunability of their polymeric network structure. In this study, crosslinked chitosan‐tripolyphosphate (CS‐TPP) nanocarriers were formulated and optimized using a Box‐Behnken design to test how different formulation parameters affect the properties of the nanoparticles. The improved formulation made nanoparticles that were less than 452 nm in size and had high entrapment efficiencies (>87%). FTIR, XRD, DSC, SEM‐EDX, and DLS all showed that a crosslinked polyelectrolyte network had formed and that divalent metal ions (Fe ^{2 +} , Cu ^{2 +} , Zn ^{2 +} ) had been successfully added. We used swelling analysis and release experiments to look into the connection between network structure and transport behavior. The nanocarriers showed a biphasic release pattern, with an initial burst followed by steady diffusion over eight days. Kinetic modeling with the Korsmeyer–Peppas equation showed that transport was controlled by Fickian diffusion (n < 0.45). The differences in release behavior were due to differences in the strength of the metal‐polymer interaction, which changes the network's compactness and diffusion pathways. These results show that process parameters control the structure and transport properties of the network, which allows for tunable sustained release behavior.