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Crosslinked chitosan particles have been developed to improve the storage stability of bioactive proteins and to ensure adequate bioavailability by targeting release to the colon. The characteristics of these chitosan-based particles, formed using different molecular weight chitosans and different anion cross-linkers, were demonstrated using small angle X-ray scattering, ζ-potential, particle size, and morphology. An in vitro release study showed that protein release from the particles in the upper gastrointestinal tract was <30%, suggesting the possibility for target release to the colon. Some of the particles were shown to retain colon-targeted protein delivery after storage in PBS buffer. By controlling the structure of the chitosan-based particles, it was possible to both reduce protein leakage during short-term storage and achieve colon-targeted delivery. [ABSTRACT FROM AUTHOR]

• By different crosslinker, the internal structure of CS-based hydrogel was changed. • The STPP-crosslinked CS hydrogel showed the ability of colon-site delivery. • With the hydrophilic surface and –NH 2 , the hydrogel showed well cell proliferation. • The STPP-crosslinked hydrogel was safe for colon-site delivery with cell adhesivity. Chitosan (CS)-based hydrogels with different structures were prepared to ensure the bioavailability of bioactive components. With the electrostatic interaction between CS and anionic crosslinkers, the structure of the CS-based hydrogel changed and influenced the swelling ability, which was beneficial for maintaining bioactive ingredients in the hydrogel. Compared with sodium hexametaphosphate, hydrogels crosslinked by sodium tripolyphosphate (STPP) had a higher swelling capacity and more stable release profile (no more than 10% BSA in the upper gastrointestinal tract), which could deliver bioactive ingredients to the colon. Moreover, due to electrostatic interactions, the surface of the CS-based hydrogel became hydrophilic, which helped Caco2 cells to grow on it. 118.86%–147.22% cell viability was found on the CS-based hydrogel. Furthermore, with different crosslinkers and concentrations in the crosslinking process, the release properties and safety of the hydrogels were varied, but the STPP-crosslinked CS hydrogel presented good cell adhesivity for bioactive components to the colon. [ABSTRACT FROM AUTHOR]