一、利用修飾環糊精之矽奈米線場效應電晶體作為分子感測器 二、利用矽奈米線場效應電晶體研究卵白素蛋白的結合行為

Abstract

近年來矽奈米線場效應電晶體已經被廣泛發展成為超靈敏的生物及化學感測器。由於矽奈米線本身具有可調控電學性質以及生物相容性，矽奈米場效應電晶體已成功的應用作為離子、DNA、蛋白質以及病毒的感測器。 在本研究中，我們主要分為兩個感測系統並分別討論之。第一個系統中，我們在矽奈米線表面修飾環糊精分子，而成為一個有機分子辨認感測器。環糊精是由D(+)-比喃葡萄醣單元以α-1,4-glucoside連結而成的環狀化合物。常見的環糊精含有六到八個單體，外觀類似一個截去尖端的中空圓錐體。環糊精利用內部空腔和分子形成非共價性作用力的結合。目前已經有文獻出現類似的研究，他們利用環糊精分子修飾在奈米碳管場效應電晶體上，以偵測目標分子。然而，其偵測機制仍然不是很清楚。因此我們利用矽奈米線場效應電晶體做偵測工具，以對其感測的機制作更多的了解。 第二個系統，我們利用矽奈米場效應電晶體研究卵白素與生物素的結合行為。根據過往的文獻指出，卵白素與生物素之間會生成一個很強的作用力，其解離常數Kd ≈ 10-15 M。在流體實驗中，通道的質量傳遞效應對卵白素與生物素的結合行為有很大的影響。比較初步的實驗結果以及理論的計算證明，在低濃度時卵白素的結合行為受到質量傳遞的控制，但在高濃度時則是受到卵白素與生物素反應速率的限制。因此我們可以知道當溶液稀薄時，其結合反應會因為質量傳遞而受到控制。我們希望此研究的方法，能繼續使用在其他生物系統上，以了解影響分子與分子間之結合行為的主要因素。

In the past few years, silicon nanowire field-effect transistors (SiNW-FETs) have been widely constructed as ultrasensitive biological and chemical sensors, because of their tunable electrical properties and biocompatibility. Successful applications of SiNW-FET sensors have been developed for detecting ions, DNA, proteins, and virus. In this work, we studied two sensing systems. The first one is that a SiNW with its surface modified by cyclodextrin molecule can be viewed as organic molecular recognition sensor. Cyclodextrins compose of 5 or more α-D-glucopyranoside units linked 1→4, as in amylase. Typical cyclodextrins contain a number of glucose monomers ranging from 6 to 8 units in a ring, creating a cone shape. It is well known that the molecule is captured in the cyclodextrin cavity by non-covalent forces. Some similar studies are performed by carbon nanotube-FETs. However, the sensing mechanism is still unclear. It is interesting to understand the sensing mechanism with cyclodextrin-modified SiNW-FET. The other one is the investigation of the binding of avidin to the biotin modified SiNW-FET (termed biotin/SiNW-FET). The dissociation constant of avidin-biotin is measured to be Kd ≈ 10-15 M. We delivered avidin to the biotin/SiNW-FET surface by injecting an avidin sample into a microfluidic channel system. We measured the response times of biotin/SiNW-FET to avidin at various concentrations. The vi experimental results were explained by a theoretical model, considering that the avidin molecules move to the surface of biotin/SiNW-FET by mass-transfer, diffusion, and convection. That mass-transfer controlled behavior for avidin is dominant in lower concentration condition. For higher concentration, the response time may be limited by the binding rate of avidin onto the biotin/SiNW-FET, instead of by mass-transfering to the biotin/SiNW-FET. The mass-transfer-controlled model is therefore concluded valid in diluted solution.