中文摘要：

为了探讨H7K（R2）2修饰的pH敏感脂质体对U87-MG细胞的靶向作用,本文选择香豆素-6（coumarin-6）为荧光探针构建了包载香豆素--6的H7K（R2）2修饰的pH敏感脂质体（coumarin--6--PSL--H7K（R2）2）。采用流式实验分别对H7K（R2）2在coumarin--6--PSL--H7K（R2）2中的比例以及coumarin-6--PSL--H7K（R2）2在U87--MG细胞的摄取途径进行研究。采用CD技术对H7K（R2）2在pH 7.4和pH 6.8条件下的二级结构进行考察。实验结果显示,H7K（R2）2在coumarin--6--PSL--H7K（R2）2中占2.5%时,其靶向作用优于1%和3.5%。细胞摄取途径实验表明,coumarin--6--PSL--H7K（R2）2进入U87--MG细胞不受菲律平、甲基--β--CD和氯丙嗪等抑制剂的影响。H7K（R2）2在pH 6.8时的二级结构多为β--turn。本研究结果表明,在H7K（R2）2修饰的pH敏感脂质体中,H7K（R2）2的最佳比例可确定为2.5%。H7K（R2）2修饰的pH敏感脂质体进入肿瘤细胞的途径主要通过低pH条件下H7K（R2）2所产生的穿膜肽样作用。H7K（R2）2在pH 6.8条件下所出现的发卡样二级结构是其产生靶向和穿透作用的可能机制。

英文摘要：

The present study aimed to investigate the targeting effect of H7K（R2）2-modified pH -sensitive liposomes on U87-MG cells. Using coumarin-6 as a fluorescence probe, we prepared H7K（R2）2-modified p H-sensitive liposomes（designated as coumarin-6-PSL-H7K（R2）2）. The flow cytometry assay was used to evaluate the effect of H7K（R2）2 proportions on the cellular uptake and endocytosis pathways of coumarin--6--PSL--H7K（R2）2 on U87-MG cells. The circular dichroism（CD） spectroscopy assay was used to investigate the secondary structures of H7K（R2）2 peptide at pH 7.4 and H 6.8, respectively. Our results indicated that the 2.5% proportion of H7K（R2）2 in the coumarin-6--PSL-H7K（R2）2 was superior to those of 1% and 3.5% of H7K（R2）2. The uptake of coumarin--6-PSL--H7K（R2）2 on U87--MG cells was not inhibited by filipin, M-β--CD or chlorpromazine. The secondary structure of H7K（R2）2 at pH 6.8 was mostly presented as β--turn. In conclusion, we suggested that the appropriate proportion of H7K（R2）2 in the H7K（R2）2--modified pH--sensitive liposomes could be set at 2.5%. The cellular uptake pathway for H7K（R2）2-modified pH--sensitive liposomes was via the cell penetrating capacity of H7K（R2）2 which responded to acidic condition. The secondary structure of H7K（R2）2 at pH 6.8, which was presented as the shape of hairpin, might be mainly responsible for its targeting and cell penetrating effect.