食品科学及工程专业毕业论文--胆固醇对磷脂脂质体膜性质的影响.docVIP

摘 要 脂质体作为一种有效成分的载体，能够起到靶向定位，缓释有效成分，降低毒性的作用，在国内已经成功应用于冬虫夏草，人参皂苷等中药制剂的生产，国外也使用脂质体保持食品中某些特殊营养成分的活性[1]。但由于其原料——磷脂，化学性质活泼，常温下暴露在空气中就容易被氧化变质。人们发现在脂质体中加入一定比例的胆固醇溶液能够起到稳定脂质体化学性质，改善脂质体分子结构，使脂质体被氧化速率显著降低，同时能够改善脂质体膜的通透性以及流动性[2]。 在本研究中，以大豆磷脂为原料研究胆固醇-脂质体混合体系的性质。通过对脂质体体系粒径的测定，发现此混合体系的粒径先随胆固醇浓度升高而升高，之后随胆固醇浓度升高而降低。采用TBA（硫代巴比妥酸）法，测定混合体系的被氧化程度，发现添加了胆固醇的脂质体溶液被氧化速率明显降低，同时胆固醇浓度在15%以上时，被氧化速率并没有明显差异。利用荧光探针法对混合体系的微极性（I1/I3）进行研究，发现此混合体系的微极性随着胆固醇浓度的增加而减少。采用差示扫描量热法测定了脂质体的相变温度，发现脂质体的相变温度随胆固醇浓度的上升呈先减小后增大的趋势。采用DPH为荧光探针测量此混合体系的荧光偏振度（P值），发现P值随着胆固醇浓度的增加而减小，证明脂质体膜的流动性和通透性随之增强。通过一系列的实验确定胆固醇的最适浓度为15%-20%。 关键词：脂质体；胆固醇；最适浓度；粒径；微极性 ABSTRACT Liposome as a carrier of active ingredients,can be used for can targeted positioning, sustained release of active ingredients, reduce the toxic effects.It has been successfully used in traditional Chinese medicine preparations of Cordyceps sinensis, ginsenoside production in the domestic.In foreigh liposome is used for maintain the activity of particular nutrients in the food.However, due to its raw materials - phospholipids,has an very active chemically feature,it can be easily oxidized.It is found that adding a certain percentage of cholesterol in the liposome solution can stabileze the chemical nature of liposome and improve the molecular structure and the liposome oxidation rate was significantly lower.The mobility of the membrane is also improved. In this study,we use soybean lecithin as raw material to study the nature of the mix system of cholestrol and liposome. By determination of the liposome particle size, particle size of this mixed system first with the cholesterol concentration increased after lower cholesterol concentration. We use the method of TBA (thiobarbituric acid) to detemine the the degree of oxidation,we found that the oxidation rate is obiviously decreased with the addition of cholestrol,but when the concentration of cholestrol is higher than 15%,the further addition wont help to decrease the oxiation rate any more.The use of fluoresc