- 學位論文
γ-聚麩胺酸與聚乳酸組成之梳狀接枝共聚合物於藥物傳輸之研究
The Study of Comb-Like Copolymer γ-Poly (Glutamic Acid)-Poly L-Lactide for Drug Delivery
摘要
近年來高分子微胞藥物載體在藥理學上的開發與應用備受期待，如何能讓微胞更穩定於體內循環並緩釋藥物，是現今重要課題之一。 為了降低高分子的臨界微胞濃度，以提升其在人體內穩定度，並且讓enhanced permeability and retention effect發揮最大功能，著手嘗試以新穎天然高分子γ-聚麩胺酸為親水主鏈，以及通過美國食品藥物管理局（Food and Drug Administration，FDA）認可的生醫高分子聚乳酸為疏水側鏈，合成具有較高分子量的梳狀兩性高分子共聚合物（comb-like amphiphilic copolymer）。 實驗中利用苯甲醇開環L-lactide合成了具單邊芳香烃取代基團的PLA，並透過質子化方式使γ-PGA在dimethyl sulfoxide中溶解度增加，再利用carbondiimide-based的常溫酯化反應以one-step reation成功合成γ-PGLA接枝共聚物（graft copolymer）。製備微胞是利用類似溶劑揮發法，以有機相tetrahydrofuran與水相1%葡萄糖水溶液共存方式使兩性高分子在介面自組裝（self-assembly），成功製備成直徑約110nm~150nm之奈米高分子微胞，當親疏水鏈段比值為1/2時可形成最小粒徑。 電子顯微鏡下成功證明微胞的球體結構，影像中可觀察到粒子大小均勻分布在150nm左右；臨界微胞濃度分析結果顯示，當疏水鏈段總分子量增大時，臨界微胞濃度也隨之降低，且各親疏水鏈段比值之臨界微胞濃度與傳統團聯共聚物相比，均有較低的趨勢，這使得梳狀高分子在體內可能形成較穩定的微胞結構，而有利於提升藥物載體在體內之循環時間，並達到標的的功能。 以形成最佳粒徑的γ-PGLA12嘗試包覆疏水抗癌藥物paclitaxel，在不同的初始投藥量包覆效率均可達到90％，包覆藥物量最高可達6%（drug/polymer）；不同含藥量的微胞完整釋藥時間均約兩天，且藥物釋放百分比可達90％以上，唯藥物在初期驟釋的現象仍具有改善空間；細胞毒性測試結果顯示材料具有良好生物相容性，在高濃度（500ppm）下與3T3 cell培養兩天仍可維持80％的存活率，且在包覆抗癌藥物paclitaxel後能在一天內有效毒殺細胞。
並列摘要
Drug carriers are composed of polymeric micelle have great therapeutic potential. One problem need to be solved is how to make this kind of carriers have long-circulation and controlled-release ability. In order to reduce critical micelle concentration (CMC) to lift in vivo stability of drug carriers, and bring the enhanced permeability and retention effect to full play, a novel comb-like amphiphilic copolymer which is composed of γ-poly (glutamic acid)-graft-poly lactide (γ-PGLA) synthesized in this study successfully. In this research, we used carbodiimide-based reaction to graft aromatic-end poly lactide onto the protonated γ-poly-(glutamic acid). The micellar solution prepared by a pseudo-solvent-evaporation method, and the particle size of polymeric micelle was between 110nm~150nm with narrow distribution. Additionally, we found that the smallest micelle was formed when hydrophilic/hydrophobic ratio equals to 1/2. The spherical structure of micelle was identified by AFM and SEM images. For convenient storage and micellar stability, we used glucose instead of poly vinyl alcohol which has slight toxicity as the lyoprotectant to lyophilize and preserve the micelle. From fluorescence spectra, we found that the CMC would reduced with higher hydrophobic ratio of copolymers. Furthermore, γ-PGLA copolymers have lower CMCs than conventional block-copolymers in each hydrophilic/hydrophobic ratio； this result indicated that the comb-like copolymers can be expected to form more stable micelle. Paclitaxel-encapsulation results revealed that drug/polymer ratio can be considerably raised if we removed organic solvents by rotary evaporator rapidly. The result of in-vitro release study indicated the faster releasing rate in higher paclitaxel-loading micelle, this may result from that encapsulated paclitaxel will interfere with core stability of micelle. Finally, the in-vitro cytoxicity test demonstrated that this new material can be a non-toxic and efficient carrier for paclitaxel, and the paclitaxel-loading micelle was more sensitive to inhibit hela cells than 3T3 cells. Keywords: graft-copolymer, comb-like, amphiphilic, drug carrier, CMC, in-vitro release, cytoxicity