Development of tannic acid cross-linked hollow zein nanoparticles as potential oral delivery vehicles for curcumin

Sodium carbonate was proposed as a sacrifice template and tannic acid was used as a natural cross-linker to prepare hollow zein nanoparticles (HZN/T). The formulation of nanoparticles, including the amount of water, zein and sodium carbonate, were optimized by surface response methodology (Box-Behnken design). The optimized HZN/T exhibited a small dimension of 87.93 nm with a PDI of only 0.105 and a zeta potential of −39.70 mV, indicating the nanoparticles were homogenous and formed stable colloidal dispersion. Then curcumin was used as a model lipophilic nutrient to explore the encapsulation and delivery potentials of HZN/T, in comparison with hollow zein nanoparticles without tannic acid (HZN/NT) and solid zein nanoparticles with tannic acid (SZN/T) prepared under the same conditions. Generally, the encapsulation efficiency of HZN/T or HZN/NT was significantly higher than that of SZN/T. Interestingly, encapsulation of curcumin dramatically increased particle size of SZN/T by 50 nm, while it did not induce any expansion of the dimension of HZN/T due to its hollow structure. The molecular interactions between curcumin and zein nanoparticles were investigated by Fourier transform infrared spectroscopy and fluorescent spectrophotometer. The in vitro stability and release profile of nanoparticles were evaluated under the simulated gastrointestinal conditions. Although all types of zein nanoparticles showed a sustained release of curcumin, cross-linking via tannic acid played an important role to make zein nanoparticles more resistant against simulated intestinal digestion. Therefore, compared with traditional SZN/T, the HZN/T developed in this study has promising features as a potential oral delivery system for lipophilic nutrients/drugs.