Effect of chitosan molecular weight on zein-chitosan nanocomplexes: Formation, characterization, and the delivery of quercetagetin.

The impacts of chitosan with different molecular weight on the formation mechanism, structural characteristics and encapsulating properties of the zein-chitosan nanocomplexes were investigated. The results of dynamic light scattering showed that the mean size of nanocomplexes was increased and became more highly positive charge as the molecular weight of chitosan was increased. Circular dichroism indicated that the secondary structure of zein changed after its combination of chitosan. XRD confirmed that quercetagetin was successfully encapsulated into the nanocomplexes, and FTIR revealed that hydrogen bonding and hydrophobic interaction were the main forces acting among the zein, quercetagetin, and chitosan molecules. The optimized zein-Que-LCH (low molecular weight chitosan) nanocomplexes were relatively small (309 nm), positively charged (+42.5 mV), and had a high entrapment efficiency (94.9%). Moreover, encapsulation of quercetagetin within the nanocomplexes extended its half-life by 3.84- and 2.98- folds during the photo- and thermal-degradation measurements, and effectively modulated its release under simulated gastrointestinal conditions.