Construction And Biological Activity Study Of Highly Stable Soybean Peptide-nanoselenium Comple

Selenium is an essential trace element for human body.Selenium supplementation is very important for human health.Selenium nanoparticles（SeNPs）have been shown to be a form of selenium with high safety and bioactivity,but the weak stability of SeNPs limits their development and application.The study explored the effect of soybean polypeptides（SP）on the stability,hypolipidemic activity and hypoglycemic activity of SeNPs.After sodium selenite was reduced by cysteine to obtain Cys-SeNPs,SP with different molecular weights was introduced to stabilize Cys-SeNPs.The properties and binding mechanism of soybean polypeptides-selenium nanoparticles（SP-SeNPs）were studied,and the hypolipidemic and hypoglycemic activities of SP-SeNPs were comprehensively explored.The main findings were as follows:（1）SP was prepared by enzymatic hydrolysis of soybean protein isolate,and divided into different molecular weight polypeptide components by ultrafiltration:SP1（not ultrafiltration）,SP2（<3k Da）,SP3（3-5k Da）,SP4（5-10k Da）,SP5（>10k Da）.SP-SeNPs were prepared using Cys as reducing agent and SP with different molecular weights as stabilizing agent.The optimal preparation conditions were as follows:concentration ratio of Cys:Na₂Se O₃=4:1,p H=8.0,and the concentration of SP was 2.5 mg/m L.Then,the effects of SP with different molecular weights on storage stability,thermal stability,p H stability and ion stability of SeNPs were analyzed.The results showed that the SP with molecular weight more than 10k Da（SP5）had the best stability effect on Cys-SeNPs when stored at room temperature or 4℃.SP-SeNPs had strong heat resistance ability,among which SP1-SeNPs and SP5-SeNPs had the best thermal stability.The p H of the system had great influence on the stability of SP-SeNPs,and all SP-SeNPs had good stability under alkaline conditions.The stability of SP-SeNPs in Na⁺solution was better than that in Ca²⁺solution,and the ion stability of SP5-SeNPs was the best.In conclusion,SP5had the best stabilization effect on Cys-SeNPs.（2）The properties and binding mechanism of SP5-SeNPs which showed the best stability were explored.TEM and SEM observations showed that SeNPs was spherical and wrapped in SP5.The steric resistance resulting from the long chains of SP5 protected SeNPs from collision-mediated aggregation,so it played a positive role in stabilizing SeNPs.The porous surface of SP5 was conducive to the adsorption and binding of SeNPs.The results of XPS and XRD indicated that SP5-SeNPs were zero valent and amorphous.Fluorescence spectrum results showed that the fluorescence intensity of SP5 decreased significantly after binding with SeNPs,which confirmed the formation of complex between SP5 and SeNPs.FTIR and ITC analysis suggested that SeNPs mainly interacted with O^-and N^-containing groups in SP5,and van der Waals forces and hydrogen bonding were the main driving forces of SP5-SeNPs complex.The results of circular dichroism showed that the secondary structure of SP5 changed after binding with SeNPs,which confirmed the formation of hydrogen bonding between SP5 and SeNPs again.（3）The hypolipidemic activity and hypoglycemic activity of SP5-SeNPs was explored.The results showed that SP5-SeNPs had strong binding capacity of sodium cholate and sodium taulocholate in vitro.It was found that the bile salts binding capacity of SP5-SeNPs was mainly derived from Cys-SeNPs,and SP5 had a positive effect on the bile salts binding capacity of Cys-SeNPs.The bile salts binding capacity of SP5-SeNPs decreased slightly during storage,while that of SP2-SeNPs decreased significantly,which was consistent with the results of their storage stability.The maximum inhibition rates of SP5-SeNPs onα-glucosidase andα-amylase were 13.13±2.43%and 47.17±1.30%,respectively.SP5 could enhance the inhibition effect of Cys-SeNPs onα-glucosidase.Theα-glucosidase inhibition rate andα-amylase inhibition rate of SP5-SeNPs changed little with storage time,and the inhibition effect of SP5-SeNPs was always better than that of SP2-SeNPs.The results of antioxidant experiments showed that SP5-SeNPs had strong metal ion chelating ability and good scavenging ability of ABTS^·+free radical and hydroxyl free radical,the IC₅₀ values were 0.398 mg/m L,2.089mg/m L and 2.371mg/m L,respectively.The hypolipidemic and hypoglycemic experiments in zebrafish showed that SP5-SeNPs could significantly reduce the blood glucose concentration,triglyceride and cholesterol contents in zebrafish,which revealed that SP5-SeNPs had good hypolipidemic and hypoglycemic activities.