| In the previous study,it was found that two selenium-containing rice peptides,TSe MMM and Se MDPGQQ,were screened by enzymatic hydrolysis technology and had high antioxidant activity.However,active peptides are unstable during digestion and have low absorption and utilization rate in small intestine.Nanoparticle carriers prepared by electrostatic assembly of protein and polysaccharide can encapsulate and deliver food functional factors to improve their digestion,absorption and biological activity.Therefore,in this study,lysozyme and xanthan gum were used as wall materials to prepare nanoparticles,and the formation process and interaction mechanism of nanoparticles were studied.The stability and antioxidant activity of selenium-containing peptides encapsulated composite nanoparticles were studied.In vitro digestion model and Caco-2 cell transport model were established to study the digestion and absorption characteristics of complex nanoparticles in the gastrointestinal tract.The main results are as follows:（1）The formation process and interaction mechanism of lysozyme/xanthan gum nanoparticles were studied.The results showed that the formation process of nanoparticles was driven by p H,and the alkaline condition（p H 12）was more conducive to the formation of smaller nanoparticles.Alkali-combined heat treatment of lysozyme/xanthan gum composite could produce controllable size（60 nm）,high absolute potential（30 m V）,good dispersion（PDI<0.3）of nanoparticles with elliptical morphology.Xanthan gum forms the basic skeleton of nanoparticles by wrapping the polysaccharide chain on the surface of lysozyme.Heat treatment destroyed the secondary and tertiary structures of lysozyme and improved the surface hydrophobicity of nanoparticles.Under the combined action of hydrogen bonding and electrostatic force,the structure of the composite was rearranged,and the structure was transformed from a metastable structure to a stable nanoparticle system.（2）The embedding effect of lysozyme/xanthan gum nanoparticles on selenium-containing peptides was studied.The results showed that the embedding of selenium-containing peptides had little effect on the particle size,potential and microstructure of the nanoparticles.The selenium-containing peptides were mainly embedded into the nanoparticles through electrostatic interaction.The encapsulation rates of TSe MMM and Se MDPGQQ by nanoparticles were 34.35%and 37.35%,respectively,and the loading rates were 3.74%and 3.06%,respectively.Compared with the free selenium-containing peptides,nanoparticles embedded with selenium-containing peptides were stable at p H 3～7,0～200 mmol/L Na Cl and stored for 30 days.In vitro antioxidant experiments showed that nanoparticles embedded with selenium-containing peptides had good scavenging ability of DPPH·、ABTS·+、·O2-and·OH-free radicals.（3）The digestion and absorption characteristics of nanoparticles embedded with selenium-containing peptides were studied in vitro under gastrointestinal conditions.The results showed that embedding reduced the release amount of peptides in gastrointestinal tract,and the cumulative release rates of TSe MMM and Se MDPGQQ were 12.81±1.62%and 6.27±2.36%after simulated intestinal digestion for 4 h,respectively.When the concentration of selenium-containing peptides was 100μg/m L,the nanoparticles had lower cytotoxicity and better cellular antioxidant activity.Nanoparticles containing selenium-containing peptides can enter Caco-2 cells through endocytosis mediated by clathrin and cave-like pitting.The apparent permeability coefficients of TSe MMM and Se MDPGQQ were increased to（2.19±0.19）×10-6cm/s and（2.21±0.12）×10-6 cm/s,respectively,and the cumulative transshipment volume was increased to 26.04±0.52μg and 27.63±0.43μg. |
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