Controllable supramolecular self-assembly of proteins mediated by metal-polyphenols: Characteristics and their applications on encapsulating hydrophobic small molecules

This study reports the preparation of a self-assembly material for the encapsulation and delivery of hydrophobic small molecules (HSMs). Schiff base reactions and Michael additions grafted 9.53–55.68 μmol/g of tannic acid (TA) onto soybean globulin (SG), enabling controllable supramolecular interaction strength in the carrier matrix. Ferric ions (Fe 3+ ) further induced the supramolecular self-assembly of SG, forming microparticles that individually encapsulated three types of HSMs within protein hydrophobic cavities. The encapsulation amount of β-carotene, lycopene, and quercetin reached 26.1 mg/g SG, 14.3 mg/g SG and 38.3 mg/g SG under the 40 mg/g SG of initial addition amount, respectively. The HSMs also exhibited a strong colocalization with the proteins. As the effect of TA-Fe increases, the covalent interactions between TA and SG, coordination bonds between SG and Fe 3+ , and the metal-phenolic network (MPN) structures formed between TA and Fe 3+ are all enhanced concurrently, resulting in denser, more compact particle structure. Microparticles with high TA-Fe level exhibited better stabilities under extreme pH, heat and/or oxidation conditions. The structural protection of the microparticles by TA-Fe during the early stages of gastric and intestinal digestion allowed more HSMs to be released at the final stage of intestinal digestion, forming micellar structures with proteins, thereby enhancing their bioaccessibility and antioxidant capacity. Compared to the widely used emulsion carriers, the particles prepared by this method exhibited superior stability and showed promising potential for storage and transportation.