TMC包覆胰岛素脂质体的研究

 目的研究不同相对分子质量、不同季铵化程度和不同浓度的N-三甲基壳聚糖盐酸盐(TMC)对胰岛素脂质体的影响。方法用壳聚糖合成TMC；采用逆相蒸发制备胰岛素脂质体，用TMC对胰岛素脂质体进行包覆；用透射电镜和光子相关光谱及激光多谱勒测定仪测定它们的形态、ζ电位和粒径；用HPLC和超速离心法测定包封率；用胃蛋白酶和胰蛋白酶溶液实验TMC包覆脂质体对胰岛素的保护作用；用酶-苯酚法测定小鼠血糖值结果TMC的产率和季铵化程度随反应时间的延长而增大。用TMC包覆的胰岛素脂质体的ζ电位和粒径，随着季铵化程度的增加而有所下降；随浓度增加而增加。TMC的相对分子质量对ζ电位和粒径无明显影响。包封率与TMC的相对分子质量、季铵化程度和浓度相关性不大。形态均为球形或近球形。在胃蛋白酶溶液中，TMC对胰岛素溶液有一定的保护作用；而用TMC包覆胰岛素脂质体对胰岛素的保护作用有明显提高，且随TMC的相对分子质量、季铵化程度和浓度的增加而有所增强。在胰蛋白酶溶液中，TMC包覆的胰岛素脂质体对胰岛素则有较好的保护作用，且随TMC的相对分子质量、季铵化程度的增加而增强。TMC对胰岛素溶液也有较好的保护作用。在不同相对分子质量、季铵化程度和浓度TMC包覆的胰岛素脂质体中，以0.2%TMC1.51000K，0.2%和0.4%TMC2.01000 K包覆的胰岛素脂质体降血糖效果最佳。结论TMC对胃蛋白酶和胰蛋白酶都有一定的抑制作用，并可促进胰岛素口服吸收，TMC的相对分子质量、季铵化程度和浓度对其包覆的胰岛素脂质体降血糖作用有显著影响。

Hypoglycemic efficacy of TMC-coated insulin liposomes after oral administration in mice

OBJECTIVE To study the effects of TMC with different molecular weights,degrees of quaternization and concentrations on insulin-liposomes.METHODS TMC was synthesized from chitosan.Insulin-liposomes were prepared by reversed-phase evaporation.TMC coating was carried out by mixing the liposomal suspensions with the TMC solution,followed by incubation.The morphological examination of insulin-liposomes was performed with transmission electron microscopy (TEM).The particle size,ζ potential were analyzed by using photon correlation spectroscopy and laser doppler anemometry.The entrapment efficiency was determined by HPLC and ultracentrifuge.The protection of insulin from peptic and tryptic digestion was studied by HPLC.The hypoglycemic effects of TMC-coated insulin liposomes were investigated using the glucose oxidase method after oral administration in mice. RESULTS The ratios of production and the degrees of quaternization of TMC increased with prolonging reaction time.The ζ potentials and the particle sizes of TMC-coated insulin-liposomes were found to be slightly decreased while increasing the degrees of quaternization or the concentrations of TMC.The effects of molecular weights of TMC were very weak.All insulin-liposomes were of spherical or ellipsoidal shape.The entrapment efficiencies were no obvious correlation with the molecular weights,the degrees of quaternization and the concentrations of TMC.Insulin was protected from peptic and tryptic digestion by TMC-coated liposomes.The protective action was slightly enhanced with increasing the degrees of quaternization or the TMC concentrations of TMC.The peptic and tryptic proteolytic activity could be inhibited by TMC.In TMC-coated insulin liposomes,0.2% TMC 1.5 1000 K，0.2% and 0.4% TMC 2.0 1000 K-coated insulin liposomes had better hypoglycemic effects compared with the other liposomes. CONCLUSION TMC-coated liposomes reduced peptic and tryptic digestion on insulin,and enhanced enteral absorption of insulin.TMC may inhibit the peptic and tryptic proteolytic activity in nature.The molecular weights,the degrees of quaternization and the concentrations of TMC had strong effects on hypoglycemic efficacy of TMC-coated insulin liposomes.