负载β-胡萝卜素的食品级纳米乳液运输体系的生物学效价研究

Nanoemulsion delivery systems fabricated from food-grade ingredients are widely utilized to protect and deliver natural functional components. But until now according to the scientific researches, because of the lack of an effective indicator and evaluation method, the real biological fate of namoemulsions loaded with nutraceuticals in the human GI trace is still uncertain. In this research, β-carotene was chosen as a typical natural nutraceuticals, and food-grade nanoemulsions stabilized by biopolymer emulsifiers (protein and modified starch) were chosen as the delivery system model to investigate the biological fate of nanoemulsions. The biological fate of food-grade nanoemulsions loaded with nutraceuticals was equal to the bioavailability of nutraceticals (F) which was depended on the three main factors: bioaccessibility coefficient (FB), absorption coefficient (FA) and transfer coefficient (FM). So the characteristics of structure, digestion and absorption, transportation and distribution of nanoemulsions and crystallization and isomerization of β-carotene which directly influence these three factors were systematic analyzed. And the cellular and animal tests would be used to evaluate the physiological activity of nanoemulsions which was also a certification for the in-vitro tests. Based on the information, the relationship among the characteristics of nanoemulsions and nutraceuticals and the bioavailability of β-carotene will be determined. And the effective evaluation methods would be set up to predict the biological fate of nanoemulsions loaded with nutraceuticals. It would be useful to guide the construction of nanoemulsion delivery systems with high bioavailability of nutraceuticals.

食品级纳米乳液作为一种包埋载体技术，被广泛的应用于天然功能性营养素的稳态化，达到保护和运载营养素的功能。但负载营养素的食品级纳米乳液在体内的真正生物学效价究竟如何，由于缺乏准确的评价指标及方法，在现有的研究中还无定论。本项目拟选用具有代表性的β-胡萝卜素为运载营养素，以生物大分子（蛋白质和变性淀粉）稳定的纳米乳液为运输载体，系统地对营养素纳米乳液的生物学效价进行研究。首先，从影响营养素纳米乳液生物学效价F的三个关键因子（生物有效性FB、吸收率FA和转运率FM）出发，分析纳米乳液载体特性（结构特性、消化吸收特性、转运特性和分布特性）和营养素自身特性（结晶和异构化）与这三者之间的联系，并通过细胞和动物实验对体外研究结果进行验证。最终明确纳米乳液特性对β-胡萝卜素生物利用率的影响机制，获得食品级营养素纳米乳液的生物学效价评价方法，用于指导高生物学效价的营养素纳米乳液运输体系的构建。

本项目针对目前对负载营养素的食品级纳米乳液的生物学效价评价指标及方法缺乏的现状，通过细胞吸收模型和动物模型，从影响营养素纳米乳液生物学效价F的三个关键因子（生物有效性FB、吸收率FA和转运率FM）出发，对营养素纳米乳液的吸收和转运特性进行了探讨，并获得了纳米乳液载体特性（结构特性、消化吸收特性、转运特性和分布特性）和营养素自身特性（结晶态和溶解态）与最终营养素纳米乳液生物学效价之间的关系。首先，纳米乳液中所采用的生物大分子乳化剂，可通过与营养素之间的相互作用、与营养素之间的界面效应以及自身的消化特性对营养素的增溶、保留和释放特性产生影响，进而对其生物有效性（FB）产生影响。其次，纳米乳液在经过人体消化道后，营养素可通过胶束化转运和直接吸收两种模式被小肠上皮细胞吸收。对于前者，脂解是载体中营养素被胶束化的前提，所有有利于提高脂解效率的因素都会促进胶束化进程，但最终的胶束化效率还取决于由脂肪酸结构决定的营养素增溶能力以及亲和性乳化剂链段与胶束间对营养素的竞争平衡。对于后者，纳米乳液中营养素的存在状态、纳米乳液自身的粒径、表面电荷等物理化学特性均会对载体最终的细胞摄取量产生影响，进而对营养素的吸收率（FA）产生影响。最后，通过动物实验证实，载体中营养素的溶解态及高载量均可显著提高其在小鼠血液及肝脏中的累积，提高营养素的转运率（FM）。该研究结果可在一定程度上用于指导高生物学效价的营养素纳米乳液运输体系的构建。.