Polymer nanoparticles composed with gallic acid grafted chitosan and bioactive peptides combined antioxidant, anticancer activities and improved delivery property for labile polyphenols

• Gallic acid grafted chitosan-caseinophosphopeptide nanoparticle was developed.
• The nanoparticle had antioxidant and anticancer activities.
• The nanoparticle controlled release of EGCG under simulated gastrointestinal fluid.
• The nanoparticle prevented EGCG degradation under neutral or alkaline environment.
• The nanoparticle amplified anticancer activity of EGCG against colon cancer cells.

Polymer nanoparticles assembled from gallic acid (GA) grafted chitosan (CS, GA-g-CS for GA grafted CS) and caseinophosphopeptides (CPP) were developed to deliver (−)-epigallocatechin-3-gallate (EGCG) as novel functional foods. The contents of GA in GA-g-CS copolymers were in the range of 26.5 ± 1.0–126.0 ± 1.1 mg/g, with the increase of molar ratio of GA to glucosamine in CS. Compared with CS, GA-g-CS possessed much higher solubility under neutral and alkaline environments. Spherical and physicochemical stable nanoparticles assembled from GA-g-CS and CPP were obtained with particle size around 300 nm and zeta potential of less than +30 mV. The GA-g-CS-CPP nanoparticles showed strong antioxidant activity and cytotoxicity against Caco-2 colon cancer cells. The EGCG-loaded GA-g-CS-CPP nanoparticles (84–90% for encapsulation efficiency) showed improved delivery property, controlling release of EGCG under simulated gastrointestinal environments, preventing its degradation under neutral and alkaline environments, and amplifying its anticancer activity against Caco-2 cells.