Construction And Characterization Of Zein-selenium Composite Nanoparticles And Their Pickering Emulsions

Trace element selenium plays an indispensible role in the growth and metabolism of organisms.Selenium deficiency increases the risk of cancer and cardiovascular disease as well as lowers immunity.Notably,the normal range of selenium requirements of the human body is very limited,beyond which it is easy to cause selenium poisoning.The form of selenium affects its toxicity,and ionic selenite is the most toxic and common one.Several decades,selenium nanoparticles(Se NPs),a sort of red elemental selenium,has received widespread attention in food field for its good bioavailability and low toxicity.However,it is an industrial problem to find a medium that can maintain the stability of Se NPs,so as to avoid its rapid sedimentation and eventual transformation into inactive gray-black elemental selenium.Controllable intake of active selenium is also a focus of food science.With a significant amount of non-polar amino acids,zein,a hydrophobic protein,is generally recognized as safe additive for food applications.Zein nanoparticles(zein NPs)can be spontaneously formed by simply injecting the zein-ethanol solution to water through an anti-solvent method.Zein NPs has been widely used as a carrier to stabilize hydrophobic active substances.In this work,zein NPs was used as the stabilizer to construct the selenium complex nanoparticle system,and further construct the Pickering emulsion stabilized by zein-selenium nanoparticles(zein-Se NPs).The surface morphology,binding mechanism and physical properties of zein-Se NPs were systematically investigated.Subsequently,the storage stability,antioxidant activity,in vitro cytotoxicity and biodistribution of selenium in vivo were discussed.Finally,the physical properties and stability of the Pickering emulsion stabilized by zein-Se NPs were investigated.The main research conclusions are as follows:(1)Zein-Se NPs were constructed based on anti-solvent operation and redox reaction under two preparation conditions(1%acetic acid-water system,deionized water system).The particle size and zeta potential of zein-Se NPs prepared under different concentration of zein and sodium selenite were investigated.The crystal structure,microstructure and stabilization mechanism of zein-Se NPs were also discussed.The results showed that the particle size of zein-Se NPs decreased with the increase of sodium selenite and zein concentration.The main driving forces of this trend were charge repulsion and steric hindrance effect.The particle size of zein-Se NPs could be adjusted in a wide range(11 nm to 180 nm).Among them,the smallest particle size could reach 11.4 nm.The selenium was easily non-covalent combination with O-and N-of zein to form Se-O and Se-N bonds,thereby constructing a stable Se NPs system.The selenium in zein-Se NPs exhibited an amorphous crystal structure with 0 valence state.(2)The storage stability and p H stability of zein-Se NPs prepared under different conditions were firstly investigated.Subsequently,the in vitro cytotoxicity of zein-Se NPs was examined by Hela cells and L-02 cells.Meanwhile,the protective effect of zein-Se NPs on Hela cells under H₂O₂-stress was explored.Finally,bioaccessibility was analyzed and discussed by the selenium content in the mouse organs after intragastric administration.The results showed that zein-Se NPs with smaller particle size had higher storage stability,and zein-Se NPs _H was more sensitive to p H.The DPPH scavenging capacity of zein-Se NPs in both systems remained high level after 30 days of heat treatment.Zein-Se NPs showed extremely low toxicity and even significant effect to promote cell proliferation at some concentrations,indicating the good cytocompatibility of zein-Se NPs.Zein-Se NPs also showed potential selectivity for cancer or non-cancer cells.In vivo experiments confirmed that selenium in zein-Se NPs could be absorbed after oral administration.(3)Zein-Se NPs was used to prepare selenium-Pickering emulsions.The synthesis process of the Pickering emulsion was first optimized under the guaidence of microstructure,encapsulation efficiency of oil and selenium content of the emulsion,and the shear rate of 14 krpm/min was selected for further study.The increase of zein concentration had a positive effect on the encapsulation efficiency,rheological property and oxidation resistance of Pickering emulsion.The micromorphology of the emulsion was demonstrated by using electron microscope,confocal laser scanning microscope and scanning electron microscope,the Pickering emulsion synthesized in this study was considered to have a double-layer structure.The results showed that zein could stabilize Se NPs and transport it to the oil-water interface during homogeneous operation.Subsequently,zein prevented the ineffective accumulation of Se NPs at the oil-water interface and enhanced the physical property of the emulsion.The selenium of Pickering emulsion showed skin permeability in in vivo experiments.This study provides a new strategy for preparing Se NPs with controllable size and stable performance by zein and also provides a theoretical basis for the development and suitable application of zein-Se NPs,meanwhile,selenium-containing Pickering emulsion are firstly proposed.The complex particles and its stabilized emulsion are anticipated be further used as food fortifiers or medicines.