| 摘要: | 本篇論文包含三個部分，研究主題為以綠色化學合成金屬有機骨架材(Metal-Organic Frameworks, MOFs)及其酵素複合質料之化學生物學探討，在第一部份的研究中，我們提出原位創新合成法可較有效的限制酵素的構型，進而提高其生物活性上的穩定，在此酵素構型被侷限於MOFs中之概念下，本研究以過氧化氫酶包覆於MOFs之中，通過變性劑及過氧化氫分解酶之抑制劑對過氧化氫分解酶失活機制的不同，以了解受侷限後酵素三級結構的改變，並使用螢光光譜直接了解酵素的三級結構變化，結果顯示受MOFs限制之酵素的結構改變變化程度較低，因為其三級結構被MOFs侷限後無法反摺疊，酵素結構決定酵素的功能，故在這些環境下，酵素侷限於MOFs結構之中可提升其穩定性，保持原有的酵素功能。在此，我們提出MOFs Chemical Biology的全新的概念。利用MOFs包覆生物分子來研究特定的生化現象，同時，本論文在第二部分拓展具有更大孔洞的MOFs之綠色合成法例如: University of Oslo-66，期望生物酵素能夠在其生物活性最不受影響的條件下，包覆於孔洞材料的結構之中，以利於研究其他需要大分子生物輔酶和輔因子的化學生物學課題。
第三部分延續實驗室已畢業的顏家儀學姊之研究成果，將含有醛官能基的奈米級有機金屬骨架材料─nZIF-90─利用後修飾的方式轉換為三種分別帶有羧酸、胺基、硫醇基的不同材料，分別命名為nZIF-90-C、nZIF-90-A、nZIF-90-T。在溫和的反應條件下，材料的晶形和孔洞性質得以維持，相較於先前的文獻，本研究之方法對修飾材料之孔體積有顯著的保留。並發現此系列材料具有溫和的細胞毒性，半效應濃度(EC50)約在30~70 µg/mL，經過後修飾轉換官能基的材料nZIF-90-A及nZIF-90-T，表面帶電性較修飾前提高，利於吸附在微帶負電的細胞表面上，提高其與細胞株間的交互作用，提升其作為藥物載體的潛力及為來的應用性。
;Metal-organic Frameworks (MOFs) are a versatile and ultra-porous class of materials composed of metal nodes and organic linkers, where the physicochemical properties of the MOFs can be controlled through careful selections of the inorganic or organic precursors. Therefore, MOFs show promise for a wide range of applications ranging from gas capture to biotechnology etc. Especially, the recent progress in water-based synthesis of Zeolitic Imidazolate Framework (ZIFs) opens a potential avenue for solving hazardous synthesis of MOFs. In our previous report, we proposed the green synthesis of ZIF-90 under aqueous and further demonstrated a de novo approach for embedding enzyme in structure of ZIF-90 by introducing enzyme during the MOFs synthesis. This fact imparts the functionality of micro-porosity in ZIF-90 to enzyme for shielding the bigger size of protease and allow the smaller substrate to diffuse in for enzyme catalysis.
In this thesis, we aim to study the merit provided by the de novo approach. We provide an additional benefit of de novo approach that the enzyme immobilized using de novo approach could shield the conformation of enzyme from unfolding, thus its biological function can be maintained under a wider range of conditions. We proposed this enhanced stability should be arisen from confinement of the enzyme molecules, wherein enzymes stay in additional mesoporous cavities formed by using enzyme as template. A fluorescence spectroscopy study shows that the structural conformation of the embedded enzyme with less change under denaturing conditions than free enzyme. Remarkably, we develop the concept of the MOFs Chemical Biology for probing on relationship between structural conformation and biological activity of the enzyme, and we try to expand the diversity of the de novo approach by exploring the other MOFs with larger aperture, which is allowed for diffusion of co-factors and co-enzymes in different sizes such as ATP and NADH. In this regard, we try to explore the synthesis UiO-66 in water-based system and mainly focus on their formation mechanism for realizing the syntheses of other MOFs material in aqueous solution. We suggested the solubility of organic linkers in aqueous solution can be the major concern in attempt to achieve a successful synthesis and provide ways to conquer the challenges.
Further, we continued to expand the advantages of green synthesis in ZIF-90 with reduced particles size. The nature of green synthesis repels the risk of toxic solvents still being present within the particles, thus shows their potential as a drug carrier. Also, the functionality of carriers provides methods to control drug release, yet the reported modifications suffer from largely reduced in merits, such as porosity. Thus, we demonstrated a green-based and simple method for the organic functionalization of crystalline nano-sized ZIF-90 (nZIF-90) as well as at least 25% micropore volume maintained via post-synthesis modification using optimal reactant molar ratios. The structural integrity of the original compound was preserved. The cytotoxicity of the nZIF-90 and nZIF-90 transformers around 30~70 µg/mL are moderate in comparison of those other organic and inorganic drug carriers. Thus, nanoscale MOF particles with new functionalities provide a new generation of carriers for drug delivery. |
