二元自組裝單層膜修飾之金探針與材料在水溶液中之交互作用力

Abstract

近幾年來，由於金的高生物相容性，使其在生物應用領域的研究相當的廣泛。 在金材料製程與表面修飾的不斷進步下，使金系統在材料科學、化學、生物學以及藥物學領域皆有許多創新與突破性的應用。許多研究皆顯示經過表面修飾的金基材提供一個更有效率的方式來共價鍵結生物分子 (如:質體DNA或蛋白質等)，有助於生物感測器以及生物傳輸方面的發展。然而，共價鍵結增加分子脫附的難度，限制了其應用性。 本研究中，我們將不同比例之羧酸官能基與胺基硫醇分子，在鍍金的原子力顯微鏡上修飾二元自組裝單層膜，得到一系列等電位點 (100% -COOH IEP = 3.5 ~100% -NH2 IEP = 6.3)。利用原子力顯微鏡的接觸模式，我們可以在水溶液中測量力-距離曲線，分析二元自組裝薄膜修飾的探針與自組裝薄膜修飾的矽平板表面間在不同pH值之下的交互作用力。由於表面電位會隨著pH做改變，當兩者帶同性電時，會有排斥作用力；反之，兩者帶異性電則會有吸引作用力，我們藉由控制溶液的pH值來量測其力曲線，得到其作用力的變化。 透過分析力曲線的交互作用力，我們可以知道不同等電位點的二元自組裝修飾金探針在不同pH值中的吸引與排斥現象。所以，我們可以透過控制修飾不同化學組成之自組裝單層膜來改變表面的交互作用力，提供了一個有潛力的方式來做為分子輸送系統的應用。

The use of gold substrate in Biochemistry has increasingly been the object of study for its high biologic compatibility in recent years. The continuing improvements in materials processing and surface modification of gold have led to many new and fascinating applications in material science, chemistry, biology, and medicine. A majority of studies have suggested that modified gold substrate provide an efficient way to covalently bond biologic molecules such as plasmid DNA and proteins in the fields of biosensors and biologic transportation. However, the application of covalently-bonded combination is limited by its difficulty in desorption of molecules. In this work, the gold-coated probes are modified by self-assembled monolayers (SAMs) of mixed carboxylic acid and amine functional groups in a series of ratio, and the iso-electronic points (IEPs) between 3.5~6.3 are obtained. Using the contact mode atomic force microscopy in liquid, the electrostatic interactions between modified probes v.s. APTES or modified probes v.s. SiO2 are measured at different pH values by using the force curve. Because the interacting surfaces can have the same or opposite sign of potential, repulsive or attractive interaction can be observed. Furthermore, since the surface potential is a function of pH, the observed interactions between a given set of surfaces changes with the aqueous environment. Through analyzing the electrostatic interactions, we examined the repulsive and attractive behaviors on SAMs-modified gold substrates of different IEP in aqueous environment. By controlling the interactions using SAMs of different chemical composition, this result may provide a promising mean for drug delivery systems (DDS).