壳聚糖包衣脂质体对α-糜蛋白酶降解醋酸亮丙瑞林的保护作用

Protection effect of chitosan-coated liposome on the degradation of leuprolide by α-chymotrypsin

目的 考察壳聚糖包衣脂质体对α 糜蛋白酶降解醋酸亮丙瑞林的保护作用。方法 首先通过荧光扫描和荧光淬灭实验考察脂质体对色氨酸基团的包封程度 ,然后将包封醋酸亮丙瑞林的脂质体与α 糜蛋白酶共培养 ,测定醋酸亮丙瑞林的残留量 ,同时还考察了壳聚糖对α 糜蛋白酶的吸附。结果 脂质体中醋酸亮丙瑞林发射峰强度增加 ,峰位产生 2nm蓝移。碘化钠对游离醋酸亮丙瑞林的淬灭是脂质体包封醋酸亮丙瑞林的 2 . 6 9倍 ,丙烯酰胺对游离醋酸亮丙瑞林的淬灭是脂质体包封醋酸亮丙瑞林的 2 . 2 3倍。壳聚糖对α 糜蛋白酶有一定吸附 ,但是吸附后并不改变酶的活性。与α 糜蛋白酶共培养 1h ,游离药物残留量为 0 ,脂质体中仍残留 (38 .91± 2. 39) %药物 ,而脂质体加入壳聚糖后药物残留量为 (46 . 17± 6 . 2 9) %。结论 醋酸亮丙瑞林分子中易降解基团色氨酸残留部分已插入脂质双分子层 ,壳聚糖通过聚合物的空间位阻和黏性对脂质体中药物有进一步保护作用。

OBJECTIVE: To investigate the protection effect of chitosan-coated liposome on the degradation of leuprolide by α-chymotrypsin. METHODS: Tryptophan fluorescence spectra and quenching experiments were performed to investigate the insertion of tryptophan residue into the lipid membrane. Liposomes were incubated with α-chymotrypsin to investigate the protection effect. The adsorption of α-chymotrypsin to chitosan was also studied. RESULTS: Fluorescence spectra showed that the maximum emission wavelength made a small blue shift (2 nm) and the emission intensity increased when leuprolide was entrapped in liposomes. The Trp residue in free leuprolide was 2.23 fold more accessible to acrylamide and 2.69 fold more accessible to sodium iodide than that in liposomes. The adsorption of α-chymotrypsin to chitosan had little effect on the enzyme activity. After incubation with α-chymotrypsin for 1 h, the remaining amount of drug was 0, (38.91 ± 2.39)% and (46.17 ± 6.29)% in the presence of leuprolide, liposome and chitosan-coated liposomes respectively. CONCLUSION: The more tryptophan residue entered the liposome and chitosan provided additional protection by steric hindrance of the polymer.