Development of Novel Hollow Zein Nanoparticles for Nanoencapsulation of Curcumin

In this study, 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 and fabrication process, including the amount of water, zein and sodium carbonate, were optimized by surface response methodology (Box-Behnken design). The optimal HZN/T was then comprehensively characterized and compared with solid zein nanoparticles with tannic acid (SZN/T). Our results indicated that both the amount of zein and sodium carbonate significantly affected the particle size, polydispersity index (PDI) and zeta potential, while the amount of water only had a significant effect on zeta potential. The optimal HZN/T exhibited a small dimension of 87.93 nm with a PDI of only 0.105 and a zeta potential (surface charge) of -39.70 mV, indicating the nanoparticles were very homogenously distributed with excellent colloidal stability. Then, a lipophilic bioactive compound, curcumin, was adopted as a model lipophilic nutrient to explore the encapsulation and delivery potentials of HZN/T, in comparison with SZN/T and hollow zein nanoparticles without tannic acid (HZN/NT) prepared under the same conditions. The molecular interaction between curcumin and zein nanoparticles were investigated by fourier transform infrared spectroscopy and fluorescent spectrophotometer. Associating with zein nanoparticles via hydrophobic interactions provided a hydrophobic and neutral microenvironment for curcumin. Coincidently, when loaded at the same percentage (10%), the encapsulation efficiency (95.82%) of HZN/T was higher than that of SZN/T (93.49%). The physical characteristics of curcumin-encapsulated HZN/T almost remained the same having a size of 99.55 nm and PDI of 0.101, while the SZN/T showed a significantly larger particle size (282.47 nm) and PDI (0.141). The stability and kinetic release profile of nanoparticles were tested in simulated gastrointestinal conditions. Tannic cross-linked nanoparticles were more resistant against the digestion under the simulated intestinal condition, while HZN/T showed a better retained release profile compared to free curcumin. In summary, compared with traditional SZN/T, the HZN/T developed in this study has promising features as potential oral delivery system for curcumin and other lipophilic nutrients/drugs