摘要
目的 :研究不同修饰程度和不同浓度的壳聚糖 EDTA轭合物 (CEC)包覆胰岛素脂质体的性质和口服降血糖作用。方法 :用壳聚糖合成CEC ;采用逆相蒸发法制备胰岛素脂质体 ,用CEC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其形态、Zeta电位和粒径 ;用HPLC法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考察CEC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 :当壳聚糖的D 葡糖胺亚单位与EDTA的摩尔比为 1:10时 ,CEC的粘度最高。在CEC包覆胰岛素脂质体中 ,随着修饰度的增加 ,Zeta电位和粒径稍有下降 ;随CEC浓度增加 ,Zeta电位和粒径则相应有所增加。包封率与CEC修饰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 ,CEC对胰岛素溶液具有较好的保护作用 ,用CEC包覆胰岛素脂质体对胰岛素具有明显的保护作用 ,其中以CEC2的保护作用最佳 ,且随浓度的增加而有所增强。在胰蛋白酶溶液中 ,CEC本身对胰岛素溶液有较好的保护作用 ;但用CEC包覆的胰岛素脂质体反而加速胰岛素的降解。CEC包覆的胰岛素脂质体均具有一定的降血糖作用 ,以CEC2包覆的胰岛素脂质体降血糖作用最佳 ,并呈浓度依赖性 ,其中 2
AIM:To evaluate the characteristics and the hypoglycemic efficacy of insulin liposomes coated by chitosan-EDTA conjugates(CEC) having different degrees of modification and concentrations after oral administration in mice METHOD:CEC was synthesized from chitosan Insulin-liposomes were prepared by reversed-phase evaporation CEC coating was carried out by mixing the liposomal suspensions with the CEC solution,followed by incubation The morphological examination of insulin-liposomes was performed with transmission electron microscopy (TEM) The particle size and Zeta potential were analyzed by using photon correlation spectroscopy and laser doppler anemometry The entrapment efficiency was determined with HPLC and ultracentrifuge The protection of insulin from peptic and tryptic digestion was studied with HPLC The hypoglycemic effects of CEC-coated insulin liposomes were investigated using the glucose oxidase method after oral administration in mice RESULT: A molar ratio of 1:20(D-glucosamine subunit of chitosan:EDTA) leads to an almost quantitative modification of all free amino groups A higher excess of EDTA during the coupling reaction did not lead to a higher degree of modification In contrast,a lower molar ratio than 1∶20 leads to a polymer conjugate of comparable higher viscosity The Zeta potentials and the particle sizes of CEC-coated insulin-liposomes were found to be increased with increasing concentration of CEC,but slightly decreased with increasing degree of modification The entrapment efficiencies had no obvious correlation with the degree of quaternization and the concentration of CEC All insulin-liposomes were of spherical or ellipsoidal shape In peptic solutions,CEC and CEC-coated liposomes had abilities of protecting insulin from peptic digestion,which were increased with increased concentration of CEC However,the abilities of CEC-coated liposomes were slightly lower than those of CEC In all CEC-coated liposomes,the protective action of CEC2-coated liposomes was the strongest In tryptic solutions,CEC had the ability of protecting insulin from tryptic digestion However,CEC-coated liposomes had no protective action of insulin,even it could enhance digestion of insulin All CEC-coated liposomes had definite hypoglycemic effects,and the effect was found to be increased with increasing concentration of CEC As compared with the other CEC-coated insulin liposomes,CEC2-coated insulin liposomes have better hypoglycemic effects The minimum blood glucose was 39 3% of the initial blood glucose The blood glucose reducing effect could last 4 h after oral administration by mice CONCLUSION: Proteolytic activity of pepsin and trypsin could be inhibited by CEC CEC-coated liposomes could enhance enteral absorption of insulin Degree of modification and concentrations of CEC were well correlated with the hypoglycemic effect of CEC-coated insulin liposomes
出处
《中国药科大学学报》
CAS
CSCD
北大核心
2004年第5期417-423,共7页
Journal of China Pharmaceutical University
基金
国家自然科学基金资助项目 (No 3 993 0 2 0 0 )~~
