Protein-lipid composite nanoparticles for the oral delivery of vitamin B12: Impact of protein succinylation on nanoparticle physicochemical and biological properties

Protein-lipid composite nanoparticles featuring three-layer structure (protein layer, alpha-tocopherol layer and phospholipid layer) and an inner aqueous compartment have been developed recently as a delivery system for hydrophilic nutraceuticals. These composite nanoparticles overcome many shortfalls of sole protein or lipid nanoparticles, however, exhibited poor stability during storage and high burst release in the intestinal environment. In this study, the performance of these nanoparticles was improved by modifying the protein outer layer through succinylation. The increased surface charge and spatial extension of succinate chain on nanoparticle surface improved the nanoparticle stability in both physiological buffer and water. The crosslinking by succinate minimized the leakage of vitamin B-12 to 4.5% during one month of storage. Moreover, succinylation slowed down pancreatic digestion of the protein shell, leading to a sustainable release within 10 h in the simulated intestinal fluid. Also, the modified nanoparticle increased the uptake efficiency of vitamin B-12 over 20 folds and demonstrated a good mucoadhesive capacity. The in vivo efficacy study showed that the modified nanoparticle could correct a vitamin B-12 deficiency in a rat model more efficiently than a free vitamin B-12 supplement.