Paper Title
Zein-Based Nanoparticles as Bioactive Nanodelivery Systems: A Focus on Entrapment Efficiency

Abstract
Engineered zein-based nanoparticles as nano delivery systems have recently gained a good reputation due to the possible mechanisms to load bioactive compounds. Because it consists of three-quarters of hydrophobic and one-quarter of hydrophilic amino acid residues, zein is preferred to be loaded with hydrophobic compounds. Linking between hydrophilic compounds and zein is hypothesized to increase loading of hydrophilic amount in the particles. To confirm its ability, this research used lutein as a hydrophobic compound to be physically loaded onto the zein matrix. Due to the special ability to target folate-binding receptors on cancer cells, folic acid was selected as a hydrophilic model to covalently link with zein. Consequently, the two systems were formed into nanoparticles through a liquid-liquid dispersion approach stabilized with a combined lecithin and pluronic F127. Lutein-loaded zein nanoparticles (ZN-LT) and folic acid-covalently linked zein nanoparticles (ZN-FA) were characterized in terms of average size, polydispersity, surface charge, morphology, and entrapment efficiency (%). Zein nanoparticles with physically loaded folic acid were also fabricated for comparative purpose. The morphology of the nanoparticles was observed using transmission electron microscopy (TEM). The covalently linking was confirmed by FTIR and 1H NMR spectroscopy. The results showed that the particle diameter of ZN-LT was 216.5±29 nm, whereas the diameter of ZN-FA was 67.2±6.6 nm. The two systems had the polydispersity values less than 0.3 and zeta potential was -47.61.6 mV and -27.5±4.4 mV for ZN-LT and ZN-FA, respectively. As expected, three-quarters of hydrophobic residues of zein resulted in the high amount of lutein loaded into zein nanoparticles by electrostatic interaction and hydrogen bond (83%). Not nearly, the entrapment efficiency of ZN-FA was 35.5%, but it was significantly higher than that of zein nanoparticles with entrapped folic acid (10.5%). It indicated that covalent linking improves the hydrophilic loading ability of zein nanoparticles. Thus, zein nanoparticles could be developed for various applications in this case; it can be used as a targeting nanocarrier for drug delivery to cells over-expressing folate receptors. Index Terms - Bioactive compounds, Covalent linking, Loading mechanisms, Zein nanoparticles.