Characterization and degradation study of chitosan-siloxane hybrid microspheres synthesized using a microfluidic approach.

Chitosan microspheres can address challenges associated with poor bioavailability or unsustained drug release when used as drug delivery systems thanks to their mucoadhesiveness, which allows the drug dosage to be retained in the gastrointestinal track for extended periods. Chitosan-3-glycidoxypropyltrimethoxysilane-β-glycerophosphate (chitosan-GPTMS-β-GP) hybrid microspheres were synthetized through sol-gel processing using a microfluidic approach. Microspheres with uniform spherical shapes and sizes of approximately 650μm were obtained. The microstructures of the microspheres consisted of four different siloxane structures. The degradation behaviors of the hybrid microspheres were examined under acidic pH conditions mimicking those found in the gastrointestinal track. Microspheres with different GPTMS molar ratios were incubated under several pH conditions for 2weeks. The microspheres incubated at pH7.4 extended the lowest weight loss (27%-32%), whereas those incubated at pH1.7 and pH5.4 showed greater weight losses of 43-59% and 69-77%, respectively. The inhibition of the degradation at low pH was dependent on the siloxane network in the chitosan matrix. Phosphate was mostly released in early stages, and the released amount of silicon was dependent on the composition. GPTMS was released with a chitosan chain via the hydrolysis of a chitosan molecule. The pelargonidin was incorporated in the microspheres and the slow releasing was observed at acidic condition. The resistance of these hybrid microspheres to low-pH conditions for longer than a full digestion cycle is promising for gastrointestinal drug delivery applications.