Mechanism Of Rice Protein/whey Protein Isolate Nanoparticles And Study On The Encapsulation Of Functional Ingredients

Rice proteins(RPs)are high-quality plant proteins with abundant sources and balanced nutritional value.However,more than 80%of RPs are gluten,resulting in low solubility of RPs and low commercialization levels.The traditional method to modify the RPs is ineffective,which restricts the industrial development of RPs.Aiming at the current problems,the pH-recycle method was used to construct a whey protein isolates(WPIs)-RPs complex system(WRPs)with respect to hindering the structure refolding of RPs during protonation,and the molecular mechanism of their formation was analyzed;The self-assembly behavior of WRPs and eugenol was explored,and the micromorphology of self-assembled nanoparticles(WRPs SNs)was characterized;The formation mechanism was analyzed from thermodynamical,interfacial,and structural characterizations.With paclitaxel(PTX)as the active compound model and self-assembly as the medium,the active compound-loaded vehicle(PTX@WRPs)was constructed,and the bioactivity of PTX@WRPs was determined by in vitro and in vivo experiments.This study aimed to provide theoretical guidance for the commercialization of WRPs in food,medicine,and other industries.The specific research contents are as follows:Firstly,RPs and WPIs were deprotonated under alkaline conditions and then was neutralized to pH 7.0.After centrifugation,dialysis,and freeze-drying,the WRPs could be obtained.Compared with the control RPs,the solubility of which in WRPs was increased by more than 25 times,up to 54.08%.Although the WRPs were turned into nanoscale particles,the primary structure of the two proteins was retained entirely.The molecular investigation showed that RPs and WPIs formed a new synergistic structure,in which WPIs and RPs interacted via their backbones during acidification;The electrostatic interactions,hydrogen bondings,and hydrophobic interactions contributed to the anti-folding effect of proteins during protonation,while higher surface potentials(-32 mV)enable the stabilization of WRPs in water.Moreover,WRPs have a more balanced nutritional value than RPs and WPIs.Secondly,based on the self-assembly characteristics of WRPs and eugenol,the structure of self-assembled nanoparticles(WRPs SNs)was studied.WRPs and eugenol can form a series of nanoparticles with an average particle size in the range of 140.6?165.8 nm under low-speed stirring in deionized water.For WRPs:Eugenol=1:3(w/v),the polydispersity index(PDI)was the lowest(PDI<0.2).The encapsulation of eugenol could reach 395.71 ?g/mg protein.According to the shape factor(Rg/R/h),WRPs SNs were spherical,and the interior density was greater than the exterior(Rg/R/h<0.775).More hydrophobic residues in WRPs triggered better interface activity of WRPs.The interfacial tension(?)between eugenol and water was reduced by 89.50%by WRPs.Thermodynamics characterization showed that the self-assembly was a spontaneous behavior that was exothermic with increased entropy dominated by non-covalent,hydrophobic interaction.Meanwhile,the secondary structure of WRPs remained unchanged.The hydrophobic interaction in self-assembly was mainly affected by the tryptophan and lysine residues in the proteins,where the microenvironment varied greatly.The active compound,paclitaxel(PTX),vehicle(PTX@WRPs)was successfully prepared by self-assembly with PTX loading of 27.13 mg/g protein.In vitro experiments showed that WRPs coated around the HepG-2 cell surface and then entered the cell by translocator.PTX@WRPs significantly reduced the 48-h IC50 of PTX against HepG-2 cells from 0.264?g/mL to 0.012 ?g/mL.In vivo experiment showed that the free WRPs group had no significant inhibitory effect on tumor cells.Compared with the free PTX group,the tumor volume of PTX@WRPs group decreased by 30.70%,and the tumor inhibition rate reached 59.12%.Significant liver tumor metastasis was observed in the control group and the free WRPs group,whereas negligible metastasis was observed in the free PTX group and WPTX@WRPs group.The influence of PTX@WRPs on mouse liver was lower than that of free PTX.The above results showed that the construction of WRPs nanoparticles could effectively improve the solubility of RPs and accelerate the commercialization of RPs.At the same time,given the self-assembly characteristics and encapsulation effect of WRPs and eugenol,it will help to further develop the field of functional carriers and provide more alternative natural carrier materials for bioengineering,pharmaceutical and other industries.