葉酸標靶遞送抗拓樸酶奈米化藥物在腫瘤細胞之療效分析

Optimizing folate-targeting nanoparticles for etoposide delivery

蔡亞霖(Ya-Lin Tsai)

指導教授 ： 張富雄

國立臺灣大學/醫學院/生物化學暨分子生物學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.10352

摘要

在腫瘤治療方面，標靶作用廣泛被運用在各種的奈米粒子上，且幾乎已成為研究中必備的方式。其好處就是可以減少與非標靶目標之非專一性的結合，因此常被應用在攜帶藥物、質體或是短鏈核苷酸方面，用以增加攜帶物之作用效率。葉酸在生物體中參與核酸以及胺基酸之合成，為一個常見的標靶配體，能與細胞膜上的葉酸受體結合，並以細胞內吞作用將奈米粒子攝入細胞中。有研究指出，相較於健康的正常細胞，在腎、腦、肺、乳癌中會有大量表現之葉酸受體存在。所以藉由葉酸作為標靶配體，是一常被利用來研究的材料。
本實驗利用化學合成的方式將葉酸連接於膽固醇上作為標靶脂質，並與以膽固醇為基礎的正價脂質 (GEC-Chol)、膽固醇混合製備成以膽固醇為基礎之脂微粒 (GCC)。由於脂微粒有著高的生物相容性、可大量包裹疏水性藥物、相較微質體有著穩定之結構，而且比固體脂質奈米粒子的徑粒大小較微小等特性，所以適合作為新一代攜帶藥物之載體。本實驗透過將此有標定葉酸之GCC處理細胞後，使用螢光顯微鏡、雷射共軛焦顯微鏡以及流式細胞儀進行螢光量之統計分析得到葉酸標靶的結果。另一方面，將GCC包裹拓譜異構酶Ⅱ之抑制物依託泊苷，所得到之脂微粒大小約為70-80奈米，藥物包覆率可達50 % 左右。在細胞攝取以及細胞毒性之測試，可發現帶有葉酸標靶之GCC攜帶的藥物相較只有依託泊苷處理下，所造成之細胞毒性可增加約20 %，並且若額外加入的20 μM的葉酸後會出現競爭性的效果。
本論文除了將葉酸標定在GCC上，也探討一些脂微粒之基本性質，如GCC中脂質之比例如何影響粒徑大小、脂微粒在GEC-Chol: Chol= 1:3的比例下，聚乙二醇之最大承載量為50%，以及GCC上若有20% 的聚乙二醇存在下，即可阻擋GCC在磷酸緩衝生理食鹽水中凝集之現象。期望在未來，以膽固醇為基礎之GCC能夠運用在更廣泛之用途，並能改善現階段在奈米材料應用上的不足。

關鍵字

標靶治療 ； 葉酸標靶 ； 脂微粒 ； 聚乙二醇 ； 葉酸共價膽固醇 ； 依托伯苷

並列摘要

Targeted therapy is widely used in a variety of nanoparticles in cancer therapy. By its specificity, ligand-modified nanoparticle delivery systems have been used for delivery of drugs, plasmid, and siRNA. Folate plays an important role in the biosynthesis of nucleic acid and amino acids and it’s one of the common targeting ligand for many cancer cells via receptor-mediated endocytosis. It has been found that FRs are highly modified levels in kidney, brain, lung, and breast carcinomas but very low levels in most normal tissues. Moreover, targeting FRs through folate conjugation is an attractive strategy.
First, it fabricated the major lipid, GEC-Chol which is a kind of cationic cholesterol-based lipid, and Folate-PEG-Cholesterol by chemical synthesis. Then, mixed with cholesterol to prepare our cholesterol-based nanoparticles (GCC). It has some characteristics that can be a new generation of carrier, including highly biocompatible, being able to carry large amounts of hydrophobic drugs, stable structure compared to the Liposome, and small size relative to soild lipid nanoparticles. After treating cells with folate targeting GCC, it used fluorescence microscopy, laser confocal microscopy and flow cytometry to detect the amount of fluorescence in cells and analysis statistical results. For further determine the effectiveness of folate targeting, etoposide was loaded in GCC, which is the inhibitor of topoisomeraseⅡ. The size of GCC is around 70 - 80 nm, and drug encapsulation efficiency is about 50%. In cell uptake and cytotoxicity test, it is found that if GCC has folate ligand, it can make the survival rate of cell reduced around 20%, but it will appear competitive after added additional 20 μM folate.
On the other hand, the study also discussion on some basic physical properties of GCC like the effects of different lipid ratios can adjust particle size; it is found that GCC with lipid molar ratio of GEC-Chol: Chol= 1:3, the maximum carrying capacity of polyethylene glycol (PEG) is about 50%; and in the presence of 20% PEG on GCC, it could block aggregation of GCC in PBS. We expect that the cholesterol-based micelle will be used widely in the future, and can improve the inadequate in nanomaterial applications.

並列關鍵字

targeted therapy ； folate targeting ； lipid micelle ； folate-PEG-cholesterol ； PEG ； etoposide

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