Structurally stable sustained-release microcapsules stabilized by self-assembly of pectin-chitosan-collagen in aqueous two-phase system

Microcapsule colloidal systems have been widely used as delivery vehicles. Natural biopolymers are highly biocompatible shell materials for the fabrication of microcapsules, but no single substance can fulfill the requirements of aqueous two-phase interfacial assembly. In this study, we fabricated pectin-chitosan-collagen composite microcapsules (PCCMs) in an aqueous two-phase system to improve the robustness and sustained-release capacity of resultant microcapsules. Fourier transform infrared spectra and isothermal titration calorimetry thermodynamics analysis indicated that the PCCM interface can be stabilized by pectin, chitosan, and collagen via intermolecular electrostatic interactions and hydrogen bonds. The swelling experiment and atomic force microscopy nanoindentation measurements demonstrated that the PCCMs had excellent anti-swelling performance and enhanced mechanical strength of the composite interfacial membrane. Contraction-recovery measurements and scanning electron microscopy indicated that the PCCMs exhibited prominent anti-shrinkage capacity and restorable surface smoothness. The release kinetics of encapsulated substances under conditions of different osmotic pressure and salt concentrations revealed that the PCCMs had superior sustained-release capacity. This study yielded natural, biocompatible, and robust aqueous two-phase microcapsules for encapsulation and delivery of active biomacromolecules.