LF脂质体在婴儿体外消化的控释机制及其与结构特性关系

The digestion of nutrients and their delivery system in gastrointestinal track is highlighted in food area recently. In our previous studies, the structure of membrane and release of core molecules from liposomes displayed significant difference between in simulated gastric fluid and in small intestinal fluid during in vitro adult digestion. However, the release mechanism and its relationship with liposomal structure in special populations such as infant have not been yet studied. Therefore, an improved thin-layer dispersion method is used to prepare liposome entrapped a model protein—lactoferrin (LF), which is an essential nutrient of infant, in this project. The properties of control release mechanism and structure of LF liposomes are studied during in vitro digestion of infant, with the digestion of adult a control. Release properties include disruption degree of particles (particle integrity and diffusion coefficient), wall materials degradability (oxidative stress and lipolysis), and core molecules release kinetics (SDS-PGAE images and leakage rate); while structural properties are appearance (color difference and relative turbidity), particle structure (size and distribution, surface charge and interaction of particles) and membrane structure (functional group and morphology). Mathematical models are established based on Fick’s first flow to clarify the release kinetics of LF liposomes during in vitro infant digestion. Moreover, the relationship between release mechanism and structure of liposomes is established by multi-factors correlation analysis. This project would provide more technological knowledge for control release of liposomes during in vitro digestion and theoretical guidance for regulation and tailor other food delivery system on structure and function for infant GI digestion.

营养物及其运载体系的胃肠道消化是当前食品领域的研究热点。前期研究发现，脂质体在模拟成人胃和小肠消化的结构及芯材释放差异显著，但在特殊人群如婴儿环境的控释机制及其与结构特性关系尚不明确。本项目拟以婴儿必需营养素乳铁蛋白（LF）为模型芯材，采用改良薄膜分散法制备脂质体；以成人为对照，研究LF脂质体在婴儿体外消化的释放特性和结构特性，前者包括颗粒整体破坏度（颗粒完整度、扩散系数）、壁材降解度（氧化应激、脂解作用）和芯材释放动力学（分子成像、泄漏率），后者包括外观（色差、相对浊度）、颗粒结构（粒径与分布、表面电荷、颗粒间作用）和膜结构（官能团、微观结构）；基于Fick’s定律建立数学模型阐析LF脂质体在婴儿体外消化的控释机制，通过多因素相关性分析揭示脂质体控释机制与结构特性关系。本项目将为丰富脂质体在不同人群消化的控释理论提供参考，为其它运载体系在婴儿胃肠道消化结构与功能的可调控性提供技术借鉴。

食品营养物在人体胃肠道消化过程中的结构性质变化一直是人们密切跟踪的研究热点，作为一种具有类细胞结构的两亲性运载体系，脂质体对包埋物具有保护、缓释和靶向等作用，但当前针对食品级脂质体的消化研究甚少，特别是在特殊人群（如婴儿）胃肠道中的释放机制及其与结构特性的关系等一些重要的科学问题缺乏认识。本项目以婴儿必需营养素乳铁蛋白（lactoferrin，LF）为模型芯材，以成人为对照，分析LF脂质体在婴儿体外消化的颗粒完整度、壁材破坏度和芯材释放动力学；通过表征LF脂质体消化后的外观、颗粒和双分子层膜等结构特性，结合胆固醇和蛋白质对脂质体结构影响规律，揭示脂质体消化的控释机制与结构特性关系。研究结果表明：（1）LF脂质体的平均粒径和zeta电位分别约为1295.5±102.5 nm和-10.6±0.83 mV，通过超高速离心结合SDS-PAGE法，测得LF脂质体包封率约为52%；（2）脂质体在婴儿体外模拟胃和小肠消化研究表明，在模拟胃部消化过程中随着消化时间延长，LF脂质体的颗粒结构、光学性质变化较小；磷脂的膜结构基本保持不变，而且包裹的蛋白质释放较少，经婴儿环境消化120 min蛋白质的残留量为74.3%；（3）在模拟小肠消化过程中，LF脂质体的颗粒结构、游离脂肪酸的释放量和磷脂膜的氧化程度均随着消化时间延长而发生明显变化，而且乳铁蛋白也逐渐被释放水解，在婴儿模拟小肠中消化120 min蛋白质的剩余量仅有25.8%；（4）胆固醇的存在能提高脂质体磷脂双分子层在消化过程中的稳定性，正电荷蛋白质覆盖在脂质体表面能降低脂质膜的稳定性并且显著加快脂质体降解。本项目可为丰富脂质体及其它运载体系在不同人群的消化研究提供技术借鉴，为脂质体在婴儿胃肠道消化的结构与控释功能有效调控提供理论指导。