金電極於免疫球蛋白G抗體偵測之交流阻抗分析與電性模型

Abstract

本研究主要是在探討以延伸式閘極結構之金電極最佳化修飾條件及量測方式。首先在金電極圖案上修飾自組裝單分子層(Self-Assembled Monolayer, SAM)，再將生物分子固定於改質過後的分子層上，並量測修飾生物分子其電化學阻抗變化。為了達到良好的選擇性修飾，透過聚乙二醇矽烷(PEG-silane)來降低非專一性吸附，以提高元件偵測靈敏度，以循環伏安法驗證所修飾的分子層未具有氧化還原反應，而藉由螢光變化量來驗證所修飾的生物分子螢光亮度情形，從螢光變化量可以分辨出五個等級變化量(1mg/ml~100ug/ml)。模擬結果顯示藉由電化學阻抗變化推斷其等效電路圖形，最後模擬出不同濃度生物分子所造成表面電位變化，透過表面電位大小來斷定生物分子的含量；此外，將交流電訊號施加在參考電極上並觀測金電極的訊號，發現在低頻下能觀察到不同濃度的生物分子變化量，而金電極面積越小其表面電位變化量越大，其變化量為uV等級。此外，本論文藉由「阻抗匹配」方式來提高偵測元件閘極端實際量測到由生物分子造成表面電位之變化量，以此提高實際量測生物分子偵測靈敏度，使提高mV等級之變化量，因此改善閘極所感應之表面電位變化量，從實驗結果我們相信此研究對延伸式閘極系統量測會有重大的幫助。

In this research, optimized conditions of gold electrodes for surface modification and detection measurement were carried out. Self-Assembled Monolayer (SAM) were deposited on patterned gold electrodes, and biomolecules, Gluataraldehyde (GA) and Antibody were then bond on the SAM , and finally the electrochemical impedance (EIS) measured. To approach better selective modification the Polyethylene glycol-silane was used to decrease the non-specific binding of Antigen (Ag) on oxide surface. The cyclic voltametry (CV) and fluorescence were adopted to characterize the surface modification. CV results showed that no redox reaction was observed after SAM modification on gold electrodes. The intensity of fluorescence of Ab-Ag binding can distinguish 5-order of Ag concentrations. The simulation depended on equivalent circuit derived from the measurement of EIS show two important results. First, surface potential derived from the simulation has a linear relation with the Ag concentration. Second, the μV change of surface potential caused by Ag can be observed on gold electrode under an ac signal applied on reference electrode; the smaller is the area of gold electrode, the larger is the signal received on gold electrode. In addition, impedance matching was performed to increase the surface potential of gold electrode to mV. The results of this research provide a solid base for using gold electrodes as extended gates for Field-effect transistors in biosensing applications.