本研究主要是製備具溫度應答性、酸鹼應答性及生物可分解性之高分子poly(N-isopropyl-acrylamide-co-methyl acrylic acid) （PLA-g-P(NIPAAm -co-MAAc)）接枝共聚物，及具免疫隱蔽性與生物可分解性之高分子poly(2-ethyl-2-oxazoline)-b-poly(D,L- lactide) ( PLA-PEOz)雙團聯共聚物。利用PLA-g-P(NIPAAm-co- MAAc)與PLA-PEOz兩種雙性共聚合物製備複合型高分子微胞，設計一同時具有環境應答及免疫隱蔽性之複合型高分子微胞，作為智慧型抗癌藥物載體。藉由高分子微胞表面改質及利用血液與細胞內酸鹼值的差異，達到提高體內循環時間與特定部位釋放藥物之效果。並利用兩者臨界微胞濃度的差異，來探討複合型高分子奈米微胞形成之機制。研究結果顯示當PLA-PEOz二團聯共聚物的臨界微胞濃度小於或約等於PLA-g-P(NIPAAm-co-MAAc)接枝共聚物的臨界微胞濃度時，則可形成完整之複合型奈米高分子微胞；而當PLA-PEOz二團聯共聚物的臨界微胞濃度大於PLA-g-P(NIPAAm-co-MAAc)接枝共聚物的臨界微胞濃度時，則無法形成完整之複合型高分子奈米微胞。由於複合型高分子奈米微胞內核由疏水性高分子PLA所組成，因此可用以包覆疏水性抗癌藥物doxorubicin (free base)。本研究所製備之含doxorubicin複合型奈米高分子微胞由體外藥物模擬釋放研究中，可發現在37℃且pH 7.4之環境下可以有效的保護藥物，而在37℃且pH 5.0時則可快速將藥物釋放，達到環境應答之功能。利用人類子宮頸癌細胞HeLa cells與複合型高分子奈米微胞進行細胞培養實驗，結果顯示複合型高分子奈米微胞具有非常良好之生物相容性；而在細胞毒殺實驗中，複合型高分子奈米藥物微胞對於人類子宮頸癌細胞亦有非常良好之抑制其增生之效果。共軛焦顯微鏡影像證明複合高分子微胞結構在細胞內酸性胞器被破壞，藥物成功地在細胞質內被釋放。由於胞飲作比擴散作緩慢，所以藥物微胞的生長抑制效果比直接使用doxorubicin慢。因此，本研究所製備之複合型高分子奈米微胞，可有效改良原有之高分子微胞之表面特性，使其具有較佳之生物相容性，又同時保有其原有之環境應答功能。並為未來藥物制放系統提供一個新的發展方向。

In this study, poly(N-isopropyl acrylamide-co-methyl acrylic acid) (PLA-g-P(NIPAAm-co-MAAc) graft copolymer with thermal sensitivity, pH sensitivity and biodegradability was synthesized by free radical polymerization from NIPAAm monomers, MAAc monomers and PLA macromonomers. Additionally, poly(2-ethyl-2-oxazoline)-b-poly(D,L- lactide) (PLA-PEOz) diblock copolymer that can be avoided mononuclear phagocyte systems recognition was synthesized by ring opening polymerization. A novel nanostructure, which was called mixed micelle, was prepared from PLA-g-P(NIPAAm-co-MAAc) and PLA-PEOz by a solvent exchange process. This nanostructure not only provide a particle modification technique to hide the inner structure from graft copolymer or to prepare a stealth micelle for avoiding the recognition by the physiological system, but also provide a environmental sensitive core to control the anticancer drug released for application in cancer therapy.
This study was divided into two sections. In the first section, the difference of critical micelle concentration (CMC) of each copolymer was used to study the formation mechanism of mixed micelles. From our study, the completely mixed micelle was formed as the CMC of diblock copolymer was lower than or equal to that of graft copolymer. As the CMC of diblock copolymer was higher than that of graft copolymer, otherwise, the mixed micelle and micelles from each copolymer were coexisted. In section two, the hydrophobic anticancer drug, doxorubicin (Dox), was incorporated into mixed micelle for used in cancer therapy. Dialysis method was conducted on the Dox and copolymer solution, and mixed micelles with Dox were formed, exhibiting a uniform particle size of 262.3 nm. From UV/Vis spectrophotometer analysis, drug content of mixed micelle incorporated with Dox was around 25 %. In vitro drug released evaluation was conducted at 37 ℃ with different pH levels. In neutral surrounding, the release of drug form mixed micelles with Dox was less, indicating that the mixed micelle was stabilized and efficiently protect the drug under such surrounding. In contrast, a significant release of Dox was observed in acidic surrounding. That is because of the P(NIPAAm-co-MAAc)s collapsed and aggregated in acidic surroundings, deforming the inner core, causing Dox to be released from the mixed micelles. On the other hand, cytotoxicities of free Dox and mixed micelle with Dox were determined by measurement the inhibition of HeLa cell growth using a tetrazolium dye (MTT) assay. The result exhibited that Dox released from mixed micelle also demonstrated pharmaceutically activity. In summary, this study presents the first example of self-assembly from diblock and graft copolymer, not only involving a particle modification technique to hide the inner structure and to increase the biocompatibility of materials, but also combining the advantages of the two copolymers to exhibit multi-functions for used in drug delivery.

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