One-step fabrication of phytoferritin-chitosan-epigallocatechin shell-core nanoparticles by thermal treatment

The inner surface and outer surface of ferritin cage provide interfaces for the encapsulation and delivery of food nutrients. Traditional methods to fabricate ferritin-nutrients shell-core nanoparticle usually apply acid/alkaline pH transition, which may cause the activity loss of the food nutrients or the formation of insoluble aggregates. In attempt to tackle these limitations, a simple one-step method was utilized to prepare the red bean seed ferritin (RBF)-epigallocatechin (EGC)-chitosan nanoparticle (REC) by thermal treatment at 55 °C. Results indicated that the apoRBF was partially uncoiled with a decrease of 5.3% of α-helix content induced by 55 °C treatment, and the EGC molecules could spontaneously permeate into the inner cavity of the ferritin with an encapsulation ratio of 11.8% (w/w). Meanwhile, the thermal treatment facilitated the chitosan attaching onto the outer surface of the ferritin by electrostatic interactions with a binding constant of 4.7 × 10⁵ M⁻¹. Transmission electron microscope and dynamic light scattering results indicated that the REC was mono-dispersedly distributed, with a diameter of 12 nm and a hydrodynamic radius (R_H) of 7.3 nm. In addition, the chitosan decorating onto the apoRBF improved the EGC stability by weakening the degradation of apoRBF against digestive enzymes in simulated gastrointestinal tract. This work is a novel attempt to fabricate shell-core nanoparticle in the encapsulation and delivery of functional molecules based on the ferritin cage in a benign condition without extreme pH changes.