環境敏感型高分子奈米材料製備(PNIPAAm/chitosan)及其於藥物釋放與金屬離子吸附之應用

Preparation of Environmentally Sensitive Nanomaterials (PNIPAAm/chitosan) and Their Applications on Drug Delivery and Metal Ion Adsorption

黃致豪(Chih-Hao Huang)

指導教授 ： 邱文英

國立臺灣大學/工學院/化學工程學研究所/博士(2014年)

https://doi.org/10.6342/NTU.2014.10933

摘要

本研究是利用化學設計與奈米技術，將環境敏感型高分子幾丁聚醣與聚(N-異丙基丙烯醯胺)加以結合，製備出奈米顆粒與奈米纖維，並分別討論其結構型態、環境應答特性以及應用於藥物控制釋放、金屬離子吸附之可行性。
(一) 核殼環境敏感型幾丁聚醣奈米顆粒合成
第一部份的目的是製備出具有核-殼結構與環境敏感性的載藥顆粒，並且粒粒徑小於100 nm。實驗設計如下:當幾丁聚醣在特定比例下的酸性溶液中會自組裝形成微胞，且表面帶正電荷。再以過硫酸鉀作為起始劑聚合N-異丙基丙烯醯胺單體形成奈米顆粒。聚合初期，由於聚合物尾端帶負電荷且幾丁聚醣帶正電荷，使得聚合物被吸引至幾丁聚醣微胞表面。接著聚(N-異丙基丙烯醯胺)在高溫下具有疏水的特性，使其高分子鏈縮進微胞中疏水區域，而形成核殼型奈米顆粒。最後，再以不同交聯方式固定外層的幾丁聚醣完成顆粒製備。另外，以螢光光譜量測臨界微胞濃度，並探討所合成顆粒之形成機制、結構型態、環境答應特性，評估適合顆粒大小作為藥物載體。實驗結果發現，幾丁聚醣/醋酸微胞系統中聚合並以戊二醛交聯之奈米顆粒(CS/HAc/NIP-GA) 具有較小的粒徑大小 (90 nm) 與高收縮比 (32.5%)。另外，將CS/HAc/NIP-GA應用於藥物釋放上，具有長時間釋放之效果，並且於不同pH環境下，釋放效果亦有所差異。
(二) 環境敏感型幾丁聚醣奈米顆粒複合纖維
第二部份以奈米纖維具有表面積大與局部釋放藥物的特點，設計出親水性高且具有酸鹼答應與溫度敏感性之載藥奈米纖維，並在化學結構上，以熱可交聯聚(N-異丙基丙烯醯胺-co-N-甲基醇丙烯醯胺)共聚物維持奈米纖維型態，提高在水溶液中的穩定性。首先，以靜電紡絲技術製備出奈米纖維並且將奈米顆粒CS/HAc/NIP-GA包覆其中，使增強其控制釋放的能力。實驗結果顯示，熱可交聯共聚高分子不但提供奈米纖維貼布的耐水性與抗拉強度，此外還具有細胞相容性。最後，將包覆CS/HAc/NIP-GA之奈米纖維應用於藥物釋放上，具有長時間釋放之效果，並且於不同pH環境下，釋放效果亦有所不同，未來將可利用在創傷貼布與細胞支架等方面。
(三) 奈米纖維膜應用於廢水處理
第三部分，利用奈米纖維具有高表面積與幾丁聚醣具有金屬離子吸附能力，設計出操作方便、容易分離之奈米纖維，並且具有高效率吸附/脫附能力與重複使用特性。首先，混合幾丁聚醣與熱可交聯共聚高分子聚(N-異丙基丙烯醯胺-co-N-甲基醇丙烯醯胺)，利用靜電紡絲技術製備出奈米纖維膜。探討幾丁聚醣與共聚物比例對纖維特性的影響。在泡水測試中，奈米纖維膜不但具有高吸水性還可維持其纖維形狀。在吸附能力上，由於奈米纖維具有高表面積，使其銅離子吸附量比同組成之薄膜高。在幾丁聚醣/共聚高分子 (50/50)組別中，銅離子吸收高達約79 ± 2 mg/g-mats。由於幾丁聚醣吸附能力具有可逆性，使其在酸性溶液中，可將離子脫附。再利用奈米纖維膜之溫感效應，在高溫低溫操作下，其奈米纖維膜脫附效率達96~100%。進一步反覆使用下，吸附銅離子四次，其奈米纖維膜仍可維持銅離子吸附量，未來將可做為過濾膜應用於銅離子吸附。

關鍵字

幾丁聚醣 ； N-異丙基丙烯醯胺 ； 奈米顆粒 ； 奈米纖維 ； 藥物釋放 ； 金屬離子吸

並列摘要

In this study, environmentally sensitive nanostructures prepared from poly(N-isopropylacrylamide) (PNIPAAm) and chitosan (CS) were designed as drug carriers or metal ion adsorbents. It contains three part researches:
In the first part, we tried to prepare core-shell nanoparticles (NPs) with the diameter approximate 100 nm in order to reduce non-selective uptake by the reticuloendothelial system. We tried to in-situ synthesize PNIPAAm in the presence of chitosan (CS) micelles to prepare the environmentally sensitive NPs. Firstly, CS was found to develop a cationic micelle-like structure in the carboxylic acid solution when its concentration was increased to above the critical micelle concentration, as evidenced by fluorescence. When the NIPAAm was polymerized in the CS micelle solution by using potassium persulfate as initiator, the produced thermally sensitive PNIPAAm with anionic chain end(s) became hydrophobic, as long as the reaction temperature was above its phase transition temperature; and therefore it would diffuse into the hydrophobic core of the CS micelles, producing CS/PNIPAAm core-shell NPs. The particle size of CS/PNIPAAm NPs could reduce to 100 nm by synthesizing in the acetic acid solution. The CS/HAc/NIP-GA with average diameter of 90 nm and shrinking ratio (32.5 %) was used as a drug carrier. In the drug release study, doxycycline hyclate was sued as a model drug. The results illustrated that a gradual release behavior was observed in the solutions of 25 °C and pH 7.
In the second part, the delivery systems that provide sustained release and local retention were designed to improve the efficacy of drug delivery. The thermally sensitive PNIPAAm-based nanofibrous scaffolds containing CS/HAc/NIP-GA NPs were fabricated via an electrospinning process. Firstly, thermally crosslinkable poly(NIPAAm-co-N-methylolacrylamide) (PNN) was synthesized by redox polymerization below the phase transition temperature of PNIPAAm. The phase transition temperature of the PNN copolymer could be altered from 34 to 40 oC by changing the ratio of N-methylolacrylamide (NMA) to NIPAAm. Subsequently, the CS/HAc/NIP-GA NPs were introduced into the PNN nanofibers (PNN/NPs) to achieve prolonged drug release. The nanoparticles were observed in the PNN nanofibers by transmission electron microscopy (TEM). All of the scaffolds examined had high tensile strengths (1.45 MPa or above) and exhibited no significant cytotoxicity toward human fetal skin fibroblasts. Finally, doxycycline hyclate was used as a model drug. The results illustrated that PNN/NPs nanofibrous scaffolds exhibited continuous drug release behavior in the solution of 37 °C and pH 2.
In the third part, environmentally sensitive chitosan-based nanofibrous mats with highly effective desorption, reuse ability, and easy separation were prepared for metal-ion adsorption via electrospinning. The composite nanofibers were fabricated with different mass ratios of chitosan to a thermally curable copolymer, poly(NIPAAm-co-NMA). The NMA provided the function of thermal crosslinking of the nanofibrous mats to form water-stable nanofibers in aqueous solution. Subsequently, glutaraldehyde was used as a secondary crosslinking agent to increase the gel fraction of the nanofibrous mats. The swelling ratio and gel fraction of the composite nanofibrous mats were measured. The adsorption of Cu(II) and Ni(II) on the composite nanofibrous mats was investigated. The morphology changes of the nanofibers in different environments were studied. Comparing the nanofibrous mats and films of the same material, the fibrous mats showed significantly increased adsorption of Cu(II). The adsorption amount of Cu(II) on the chitosan/PNN (50/50) nanofibrous mats could reach 79 ± 2 mg/g-mats, and its desorption was relatively effective. The incorporation of poly(NIPAAm-co-NMA) significantly improved the desorption of Cu(II) from the nanofibrous mats. The chitosan/PNN fibrous mats maintained the capacity of Cu(II) adsorption for 4-time regeneration.

並列關鍵字

chitosan ； N-isopropyl acrylamide ； self-assembly ； micelles ； drug release ； metal-ion adsorption

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