Nanocapsules formed by interactions between chondroitin sulfate and egg white protein for encapsulating hydrophilic ingredients

Nanocapsule-based technologies constitute a unique and novel research field for the food and pharmaceutical industry. The potential benefits of applying these technologies include, for example, higher bioavailability, high shelf stability, and controlled release of active ingredients. Protecting hydrophilic ingredients in food or pharmaceutical applications is crucial but challenging because of their strong tendency to leak out of the capsules into the external aqueous phase. In this study, we developed nanocapsules synthesized by electrostatic interactions between chondroitin sulfate (CS) and egg white protein (EWP). The interactions were induced by acidic conditions and continuous ultrasonication because of the contribution of the hydrogen and amide bond formation. We optimized the preparation conditions at a CS : EWP ratio of 6 : 4, in which the CS–EWP nanocapsules had an average particle size of 133.2 ± 3.4 nm with a PDI of 0.2 and a zeta potential of −25.5 mV. Molecular docking analysis revealed that the linear helix chain of CS functioned as a skeleton structure by bonding with the random coil of EWP, confirming the formation of intermolecular hydrogen bonds between CS and EWP. Scanning electron microscopy and transmission electron microscopy images revealed that the microcapsules contained irregular spheres with a core and shell structure. The encapsulation efficiency and loading content of the nanocapsules demonstrated their potential to prevent leakage of the hydrophilic ingredients because of the dense shell. Nanocapsules formed via the CS–EWP interaction provide a green and sustainable method for efficiently encapsulating various hydrophilic food or pharmaceutical ingredients.