Study On The Structure And Functional Properties Of Egg White Peptide Selenium Nanoparticles

Nanoparticles have received extensive attention due to their unique functional properties.Among them,selenium nanoparticles?SeNPs?have received special attention from the food and pharmaceutical industries.Egg white is the most common source of protein.It has high nutritional value,which is worthy of high value development and utilization.But egg white protein itself is easy to denaturation,which limits the application of egg white protein to a certain extent.In this paper,Alcalase was used to digest egg white to prepare egg white peptides?EWP?with different degrees of hydrolysis?DH?,including DH=15%and DH=30%.While reducing sodium selenite?Na₂SeO₃?to zero-valent selenium through the reducibility of EWP,red egg white polypeptide selenium nanoparticles?EWP-SeNPs?were prepared through the interaction of peptide and zero-valent selenium,and their functional characteristics a series of explorations have been carried out.The main research contents and results of this paper are as follows:?1?Using Box-Behnken response surface optimization method to obtain the preparation conditions of EWP-SeNPs:Na₂SeO₃ concentration was 6 mM,reaction temperature was82?,reaction time was 3.5 h.Observing the structure of EWP-SeNPs by scanning electron microscopy and Fourier infrared spectroscopy,selenium interacted with groups containing O and N to form Se-O and Se-N bonds,thereby obtaining stable EWP-SeNPs.By adjusting the pH of the EWP-SeNPs solution,it has better biological activity and storage characteristics under alkaline conditions.Through circular dichroism analysis,the?-helix structure in EWP-SeNPs increased,the hydrogen bonding effect was enhanced,and the secondary structure of EWP was changed,while the increase in hydrogen bonding effect increased the stability of EWP to SeNPs.Using an isothermal titration calorimeter to observe the heat change during the reaction,it was found that the binding force between EWP and Na₂SeO₃ to form EWP-SeNPs was mainly electrostatic interaction and hydrophobic interaction.The preliminary exploration of the formation mechanism of EWP-SeNPs may be that 0-valent selenium was reduced from+4-valent SeO₃^2-through redox reaction,and quickly forms EWP through the polymerization/encapsulation of EWP through Se-O and Se-N bonds-SeNPs,where the forces generated by converting Na₂SeO₃ to SeNPs were hydrophobic interactions and electrostatic interactions,and the role of hydrogen bonding was to stabilize EWP-SeNPs.EWP-SeNPs have a tendency to aggregate to spheres,and there may be hollow sphere patterns inside,which was similar to the self-assembly process.?2?The larger the DH,the smaller the relative molecular weight of the EWP and the smaller the particle size of the formed EWP-SeNPs.Through the measurement of free thiol content and hydrophobicity,it was found that the total hydrophobicity and free thiol groups of EWP?DH=15%?-SeNPs were higher than that of EWP?DH=30%?-SeNPs,but the percentage of total thiol groups exposed by thiol higher for EWP?DH=30%?-SeNPs.Antioxidant results show that the five antioxidant properties of EWP-SeNPs include reducing power,DPPH free radical scavenging,superoxide anion scavenging,hydroxyl radical scavenging,and resistance to lipid peroxidation are higher than untreated egg white.Among the five antioxidant properties,EWP?DH=30%?-SeNPs have higher reducing power,ability to scavenge hydroxyl radicals and anti-lipid peroxidation than EWP?DH=15%?-SeNPs.The ability to remove DPPH and superoxide anion free radicals is weaker than that of EWP?DH=15%?-SeNPs.It could be seen that EWP-SeNPs of different sizes have different functional properties.?3?Through the cultivation of E.coli and S.aureus by EWP-SeNPs,it was found that the inhibitory effect of EWP-SeNPs on E.coli was stronger than that of S.aureus.Low concentration of EWP-Se NPs promotes the growth of S.aureus,but Growth has no effect,and EWP-SeNPs also inhibit the growth of S.aureus at high concentrations.EWP?DH=15%?-SeNPs have a better antibacterial effect on S.aureus,while EWP?DH=30%?-SeNPs have better antibacterial effect on E.coli.?4?Through the viability test of liver cancer cells,the toxicity of EWP-SeNPs was less than that of Na₂SeO₃.The particle size of EWP-SeNPs also has a certain relationship with the amount of cytotoxicity.The smaller the particle size of EWP-SeNPs,the smaller the toxic effect on cells.Studies have shown that the smaller particle size EWP?DH=30%?-SeNPs,when the concentration was very low,will promote the growth of cells,but as the concentration increases,it gradually showed an inhibitory effect on cell growth.