2-羥基乙基丙烯酸甲酯複合物奈米結構與控制釋放行為之研究

Abstract

就許多醫療器材而言，改善其與血液接觸所產生之相容性至今日仍是相當重要的議題。高分子是目前最被廣泛應用於製造醫療元件的材料，通常需藉由改質來改善其血液相容性。許多文獻指出，表面改質方法如電漿表面改質或是肝素接枝法都已被廣泛且成功的運用在與血液接觸的元件上；然而，材料表面為較容易損壞之部分，對於需要植入體內之醫療元件，其可能因腐蝕、與血液接觸或因個人生活型態迥異而造成不同物理環境，產生非預期之化學作用，其更須具備長期穩定之特性。因此，考量醫療元件整體之功用及其在臨床治療上所面臨之問題，材料表面改質及材料整體改質仍具有許多研究及發展的空間。 本論文之研究主旨，即在於利用奈米級無機粒子與金屬粒子之混摻，探討其對於高分子水膠微結構以及整體性質之改變，與此複合材料於藥物釋放以及血液相容性上之討論。論文主體分為兩部分： 第一部分探討奈米級矽分散粒子與矽醇水合前驅物，對於2-羥基乙基丙烯酸甲酯高分子載體其微結構以及其在血液相容性之影響。我們利用即時(in-situ)光聚合法，成功製備出矽/2-羥基乙基丙烯酸甲酯 (SiO2/pHEMA and Silanol/pHEMA) 複合材。從電子顯微鏡可知，複合材料孔洞隨無機物含量遞增，含有4%奈米SiO2粒子之複合材有最佳機械性質。此外，水膠複合材之膨潤度隨無機物含量遞增，當無機物含量由2% 增加至9%，藥物擴散速率提高約100倍。經由血小板貼覆測試可知SiO2/pHEMA複合材具有相當良好之血液相容性。 第二部分探討奈米級金屬銅粒子，對於2-羥基乙基丙烯酸甲酯高分子載體其微結構以及其在血液相容性之影響。我們利用即時(in-situ)光聚合法，將銅離子均勻分散於2-羥基乙基丙烯酸甲酯高分子載體中，其後並以化學還原法，製備得到Cu(0)-pHEMA複合材。由穿透電子顯微鏡可知，隨溶劑與單體莫耳比增加，可得奈米級銅顆粒均勻分散於高分子載體，顆粒大小約為5~10nm。此外，並探討Cu(0)-pHEMA複合材中，銅溶解擴散模式以及其對於內皮細胞成長之影響。由結果可知，銅離子可經由Cu(0)-pHEMA複合材中以穩定緩慢的模式釋放，可經由複合材料組成之變化，控制銅離子釋放濃度。於體外實驗，與控制組相較，當每日銅釋放量約為10ppm時，可提升內皮細胞增長量至120%；若每日銅釋放濃度高於20ppm，則會產生毒化情形。 最後，探討Cu(0)-pHEMA複合材之電化學特性，與其行氧化作用使GSNO (Nitrosoglutathione)還原產生一氧化氮(NO)之反應探討。由循環伏安測試我們可得一氧化電流(-320mV vs. Ag/AgCl)，Cu(0)-pHEMA複合材具有氧化能力。由交流阻抗分析得知，隨Cu(0)-pHEMA複合材中之銅含量之增加至1%, 阻抗可降低至6438 ohm。在定電位測試中可知，Cu(0)-pHEMA複合材可將GSNO (Nitrosoglutathione)還原產生一氧化氮(NO)。 這個以奈米複合材微結構來控制藥物釋放之血液相容元件的研究具有很好的前瞻性。在本研究中，與血液接觸之相容性以及藥物釋放之性質同等重要，而了解複合材中無機奈米顆粒在微結構變化、表面組織及生物相容特性所扮演的角色，將有助於我們發現新的科學現象並設計更新穎的材料以應用在材料科學、生物醫學以及藥物釋放學上。

Use of medical devices with clinically acceptable blood compatibility has gained increasing attention over the years. This has been consciously alerted due to a current understanding that the devices used to contact with human blood has been criticized to having insufficient anti-blood clotting surface for short-to-long term invasion medication. Therefore, development of new biomaterials with improved blood compatibility has continuously attracted great attention. In this thesis, the incorporation of inorganic (silica) and metal (Cu) nanoparticles into the poly(2-hydroxyethyl methacrylate) (pHEMA) matrix to form inorganic/organic nanocomposites for drug controlled release and blood compatibility was achieved. The first part in this thesis, an in-situ method is developed successfully to mix well-dispersed silica colloidal suspension and silica sol-gel solution with HEMA monomers following photopolymerization to form a nanocomposite. The incorporation of SiO2 nanoparticles and Silanol into pHEMA matrix revealed a significant effect on the reaction rate of crosslinking during polymerization, resulting in composites with varying nanoporous structures. The nanocomposites showed improved tensile strength, and the platelet adhesion property remained as excellent as that of neat pHEMA, which encourages the use of such composites for antithrombotic applications. Drug diffusion characteristics in the composites can be well modulated by controlling the concentrations of SiO2 nanoparticles and silanol and water in the starting stage of synthesis. In the second part, a novel in-situ synthesis method is developed where a hybrid system based on HEMA monomers that were photopolymerized in the presence of Cu2+ precursor was prepared through an in-situ synthesis, following an in-situ chemical reduction of the Cu2+ precursor to form resulting metallic Cu-containing hybrid. The cell proliferation, surface potential, and interaction with blood of the Cu-pHEMA hybrid nanocomposites was systemically discussed. From the results, coordinated interaction between Cu(II) with the hydroxyl groups within the pHEMA matrix was confirmed by the infrared spectral analysis and considerable improvement of the thermal stability of the Cu(0)-pHEMA hybrids. Localization of the metallic copper particles within pHEMA network structure as a result of those intermolecular interactions gives rise to the formation of discretely distributed nanocrystallites with a particle size ranging from 10 to 25 nm in diameter. A relatively slow and sustained release of the Cu (in form of cupric ion) from the hybrids for a time period over 10 days was measured, which also illustrated a Cu(II)-induced proliferation of the endothelial cells. The hybrids also showed negative surface charge and considerable improvement in blood compatibility compared to neat pHEMA. Finally, the electrochemical properties of the Cu-pHEMA hybrid nanocomposites were investigated by cyclic voltammetry (CV) and alternating current (AC) impedance measurements. The generation of nitric oxide in aqueous by Cu(0)-pHEMA hybrid was also tested. From the results, the Cu(0)-pHEMA hybrid exhibits an oxidation current at -310mV. The charge transfer resistances (RCT) of Cu(0)-pHEMA hybrids are estimated to be reduced from 11743 to 6438 ohm, respectively as the content of nano copper particle in polymer matrix increased to 1 wt%. The reduction currents of Cu(0)-pHEMA hybrid varied with the concentration of nitrosoglutathione. With increasing levels of nitrosoglutathione (GSNO), the amount of NO generation increased.