Study On The Construction Of Zein-based Polyphenol Delivery Systems And Their Digestion Characteristics

Polyphenols are known as the seventh nutrient for human health and have received widespread attention for their various biological activities such as antioxidant,anti-inflammatory,and anti-cancer.However,polyphenols often exhibit limitations in practical applications such as weak stability,poor water solubility,and very low small intestinal absorption.Zein is a perfect for hydrophobic polyphenols because it contains more 50%hydrophobic amino acid residues and has special solubility and self-assembly capabilities.The development of zein-based polyphenol nano-delivery systems with good biocompatibility and self-assembly properties is an effective way to solve the above problems.In this project,zein composite nanoparticles coated with starch derivatives（debranched oxidized starch linear dextrin,hydroxypropyl-β-cyclodextrin）were prepared based on the inverse solvent precipitation method combined with an electrostatic deposition technique and used for polyphenol loading.Firstly,the physicochemical properties of the carriers and the stability of polyphenols were investigated,and the effects of debranched oxidized starch（DOS）linear dextrin and hydroxypropyl-β-cyclodextrin（HP-β-CD）coated zein nanoparticles on the encapsulation properties and stability of polyphenols were compared.Secondly,the effects of Ca²⁺cross-linked composite nano-delivery system on the co-encapsulation ability,physicochemical stability and biological activity of various polyphenols were investigated.Finally,the effects of different ion types and concentrations on the in vitro simulated gastrointestinal and digestive properties of the polyphenol composite nano-delivery system were investigated.The main research contents and results are as follows:1.In this study,zein/DOS linear dextrin composite nanoparticles（ZDNPs）and zein/HP-β-CD composite nanoparticles（ZHNPs）were prepared using an anti-solvent precipitation method combined with an electrostatic deposition technique to compare the effects of DOS linear dextrin and cyclic dextrin on the stability of zein nanoparticles,respectively.The results of Fourier transform infrared spectroscopy（FT-IR）,fluorescence spectroscopy（FS）,and circular dichroism（CD）indicated that electrostatic interaction,hydrophobic interaction,and hydrogen bonding were the main driving forces for the formation of composite nanoparticles.The experimental results of particle size and ZETA potential,scanning electron microscopy（SEM）,X-ray diffractometer（XRD）,and physicochemical stability analysis revealed that ZHNPs exhibited smaller size（143.6 nm<201.5 nm）,higher polyphenol encapsulation efficiency（89.4%>81.2%）and better polyphenol retention under environmental stress compared to ZDNPs index（RI）under environmental stress（heat treatment RI:94.1%>78.7%,storage RI:95.2%>89.0%,UV radiation RI:78.3%>57.3%）.In addition,antioxidant activity and antibacterial experiments showed that ZHNPs could effectively enhance the biological activities of polyphenolic compounds.More specifically:Compared with free polyphenols,the DPPH radical scavenging rate of the polyphenolic complex system increased by 3.66 times,the superoxide anion radical scavenging rate increased by 1.61 times,the iron reduction capacity increased by 1.74 times,and the antibacterial capacity increased by 1.84 times after encapsulation by ZHNPs.2.In this study,the structural characteristics and physicochemical properties of the composite system of co-encapsulated curcumin and quercetin after cross-linking ZHNPs(CQZH Ca²⁺)with different concentrations of Ca²⁺were further investigated.The results showed that Ca²⁺could influence the structure of the composite carriers through cross-linking,thus affecting their encapsulation and delivery ability of polyphenols.The size of the composite particles was reduced from 330.9 nm to 176.4 nm after Ca²⁺addition,and the encapsulation efficiency of curcumin was increased by 1.06 times,that of quercetin by 1.13 times,and the scavenging ability of DPPH radicals by 1.04 times.The scavenging ability of superoxide anion radical was increased by 1.53 times,and the iron reduction ability was increased by 2.29 times.The physical and chemical stability analysis of the particles showed that CQZH Ca²⁺exhibited good physical and chemical stability within a certain Ca²⁺concentration range（2 mmol/L～3mmol/L）,and its stability was also enhanced in the in vitro simulated digestion.However,in the higher Ca²⁺concentration range（4 mmol/L～5 mmol/L）,the stability of the complex system decreased significantly,which might be due to the electrostatic shielding effect triggered by Ca²⁺excess.3.Finally,this study investigated the in vitro simulated digestion characteristics of curcumin-loaded ZHNPs（ZHC）in the presence of different concentrations of Na⁺and Ca²⁺and the changes in ZHC microstructure after different digestion phases and digestion times.It was found that the Ca²⁺-induced composite particles showed better stability to pepsin in the gastric phase and gradually decomposed into a surface reticulated pore structure after exposure to the small intestine phase.This phenomenon facilitated the purpose of simulating a small release of curcumin in the gastric digestion phase and a continuous slow release in the subsequent intestinal digestion phase.In contrast,the Na⁺-induced composite particles produced adhesion between the particles after digestion and were separated to form a whole sheet-like structure,which prevented the targeted delivery and slow release of curcumin in the intestinal phase.The above results suggested that Ca²⁺can improve the encapsulation efficiency and physicochemical stability of the composite nanoparticles and improve the encapsulation,delivery,and digestion properties of ZHNPs for polyphenolic compounds.