雙甘露醣嵌配三腳架狀錨定分子的合成及探討其對氧化鋁包覆磁性奈米粒子的吸附性質

Abstract

本論文分為二部份。第一部份討論設計和合成不同的含有tri-及 monovalent anchor 的bis(mannoside) ligands。我們合成出三種不同的官能基分別作為alumina coated磁性奈米分子的錨定，這三種官能基分別為磷酸根(phosphate)、磺酸根 (sulfate)及羧酸根 (carboxylic acid)。此外利用氫氧基(hydroxyl group)作為吸附能力的實驗對照 (control)。以點擊偶合化學 (click chemistry)作為連接trivalent、 monovalent anchors及bis(mannoside) ligand。Tri-valent anchor 的bis(mannoside) ligands分子的設計分為四個部份:

第一部份為雙甘露醣給體衍生物 bis(mannoside) ligand，作用是為辨識尿道感染大腸桿細菌E. coli.受體；第二部份為以碳連組成的橋樑spacer，作用是連接bis(mannoside) ligand及上述提及的官能基non-covalent anchors；第三部份為主角，非共價鍵錨定 non-covalent anchors，用於吸附於alumina coated的磁性奈米粒子上；最後的第四部份是alumina coated磁性奈米粒子 (alumina coated magnetic nanoparticle)。我們研究了含有monovalent 及tri-valent anchor 的bis(mannoside) ligands對alumina coated磁性奈米粒子的吸附特性。 由吸附實驗中，根據Langmuir吸附模型我們發現磷酸根官能基具吸附能力，然而其他非共價錨定的吸附特性尚未明確去解釋。單一個磷酸根及三個磷酸根錨定的結合常數分別為1.15 × 10-6 M-1及1.69 × 10-6 M-1。 第二部份: 根據論文第一部份的研究成果，我們再設計用磷酸根管能基合成較簡單的carbohydrate ligands with monophosphate anchor。參照第一部份的合成策略，分別合成附有雙半乳醣給體 bis(galactose) ligand、雙甘露醣給體 bis(mannose) ligand及雙岩藻醣給體bis(fucose) ligand的monophosphate anchor。然後再以單磷酸根anchor 吸附在的磁性奈米粒子表面的特性。進一步製備含醣給體磁性奈米粒子的small library ，利用奈米粒子上醣給體 辨識尿道感染大腸桿菌E. coli的能力，進行辨識吸附的研究。

The thesis is divided into two parts, part 1 and part 2. Part I of the thesis describes the design and synthesis of bis(mannoside) ligands with mono- and tri-valent anchor, and the binding of these synthetic carbohydrate ligands on alumina-coated magnetic nanoparticles through non-covalent interactions. Three different chemical functions were chosen as non-covalent anchors, namely phosphate, sulfate and carboxylate functionalities; for comparison purpose, a mono-hydroxyl and trihydroxyl anchor were also made to serve as experiment control samples for binding studies. The design of bis(mannoside) ligands with mono- and tri-valent anchor is dissected into four portions:

(1) Derivatives contain bis(mannoside) ligands, which provide binding function for specific protein receptors; (2) a molecular spacer is inserted between bis(mannoside) ligand derivative and non-covalent anchor; (3) a selected chemical functionality is installed at the terminus, which presumably would bind to the alumina surface of magnetic nano-particles; and (4) alumina-coated magnetic nanoparticles provide binding template for carbohydrate ligands with functionalized anchors. In subsequent binding study, it was found that binding of ligands with phosphate functions follow the Langmuir adsorption model, while binding properties of other non-covalent anchors is less conclusive. The dissociation constants (kd) of monophosphate and triphosphate anchors are 1.15 × 10-6 M-1 and 1.69 × 10-6 M-1 respectively. Part 2 of this thesis is based on the findings in part 1 and explored their application. Thus different monophosphate bis(carbohydrate) ligand derivatives were prepared and successfully anchored to the surface of alumina coated magnetic nano-particles. In this study, bis(D-galactose), bis(D-mannose) and bis(L-fucose) ligand were used. To construct a small combinatorial libraries, we prepared the carbohydrate grafted nanoparticles with one type of bis(carbohydrate) ligands (□ 3), two types of bis(carbohydrate) ligands (□ 3) and all three types of bis(carbohydrate) ligands. With this small library in hand, binding studies of carbohydrate ligand coated nanoparticles to pathogenic E.coli bacteria are underway and results will be published in due course.