Camptothecin (CPT)，a kind of alkaloid with broad-spectrum antitumor activity, has significant inhibitory effect on breast cancer cells. However, camptothecin was prevented from further clinical application due to its strong hydrophobicity, unstability under the physiological environment, side effects, etc. And it is prone to aggregate in water, which lead to low loading efficiency. In order to solve these problems and make full use of its anti-tumor activity, we synthesized the reduction-responsive DCPT prodrugs, simultaneously polymerized amphiphilic PLL-PLeu decorated with RGD peptide to encapsulate the prodrugs. Pure camptothecin dimer, namely DCPT, was acquired through purification by dialysis and column chromatography after reaction with the camptothecin and 2-hydroxyethyl disulfide as reactants, then identified by 1H NMR, 13C NMR, FT-IR and MS. On the other hand, poly (lysine block leucine) copolymer (PLL-PLeu), in the proportion of 30:20, 30:40 and 30:60 between lysine and leucine, were synthesized using ring-opening polymerization initiated by hexylamine. NMR and FT-IR confirmed its structures. Prepared by dialysis method, DCPT loaded PLL-PLeu micelles were characterized with particle size, drug loading and critical micelle concentration to screen the best proportion of copolymers to be grafted by polyethylene glycol and RGD peptide. The as-synthesized RGD-PEG-PLL-PLeu copolymers self-assembled into micelles, in which process hydrophobic DCPT are loaded into its hydrophobic core. The DCPT loaded micelles were of high drug loading, encapsulation efficiency and good stability, whose size distributed in 50 - 200 nm, showed high sensitivity to reduction conditions. In addition, the results of antitumor assays in vitro suggested that the DCPT loaded RGD-PEG-PLL-PLeu micelles have stronger inhibitory effect on breast cancer cells MDA-MB-231 compared with free camptothecin. And its cellular uptake was also significantly increased according to cellular uptake assays. Therefore, the results demonstrated that the form of DCPT which under the protection of poly (amino acid) micelles could not only improve the stability of camptothecin and v greatly increase its loading capacity, but also achieve the purpose of controlled release in tumor sites, providing research foundation for the development and utilization of camptothecin and the application of poly (amino acid) block copolymers to the antitumor drug delivery system.

喜樹堿（CPT）是一種具有廣譜抗腫瘤活性的生物堿，對乳腺癌細胞具有顯 著的抑制作用。但喜樹堿的水溶性差、在生理環境下不穩定、毒副作用大，易聚 集且擔載效率低，導致抗腫瘤效果不理想。因此，本課題將喜樹堿改造成還原響 應性二聚體前藥，用精氨酸-甘氨酸-天冬氨酸序列的 RGD 肽靶向修飾的兩親性 聚氨基酸類膠束體系包載該前藥遞送至乳腺癌細胞，以期改善喜樹堿的穩定性和 擔載效率，實現腫瘤靶向和在腫瘤細胞內還原響應性釋放，最終增強喜樹堿抗乳 腺癌作用。其中，喜樹堿二聚體（DCPT）為二硫鍵連接的雙分子喜樹堿，由喜 樹堿、2-羥乙基二硫化物為原料反應得到，先後用透析法和柱層析色譜法分離純 化，再經核磁共振氫譜、碳譜、傅裡葉紅外光譜和高分辨質譜表徵確定合成成功； 兩親性聚氨基酸類嵌段共聚物先由賴氨酸、亮氨酸開環聚合反應得到PLL-PLeu， 再經聚乙二醇（PEG）、RGD 修飾得到 RGD-PEG-PLL-PLeu，通過核磁共振氫 譜和傅裡葉紅外光譜表徵，確認材料合成成功。RGD-PEG-PLL-PLeu 兩親性嵌段 共聚物在水中自組裝形成膠束，自組裝過程中利用疏水性內核裝載疏水性 DCPT， 通過 RGD 肽與腫瘤細胞表面過表達的整合素 αvβ3 受體的特異性結合，實現靶向 遞送，並在腫瘤細胞的還原環境下選擇性釋放喜樹堿。通過對載藥膠束（RGDPEG-PLL-PLeu/DCPT）粒徑、載藥量、包封率、穩定性、體外藥物釋放的考察發 現，該膠束粒徑分佈在 50 - 200 nm，具有良好的載藥量、包封率和穩定性，而且 對還原條件敏感。此外，從體外抗腫瘤實驗結果可以看出，相比於喜樹堿原藥， RGD- PEG-PLL-PLeu/DCPT 載藥膠束對乳腺癌細胞 MDA-MB-231 的抑制作用更 強，且細胞攝取量顯著提高。因此，本課題構建的基於喜樹堿二聚體和聚氨基酸 類嵌段共聚物的聚合物膠束是一種治療乳腺癌的有效策略，為喜樹堿類藥物的臨 床應用與開發以及聚氨基酸類嵌段共聚物在抗腫瘤納米遞藥系統中的應用提供 了研究基礎。