本研究於高生理鹽濃度1倍PBS下檢測心血管疾病指標，我們選定miR-126、miR-21、miR-208a及CRP作為我們心血管疾病的檢測指標。在本實驗中，AlGaN/GaN的HEMT被用來作為生物感測器的元件。以新的結構製成的HEMT元件結構導入了界面電雙層的機制，使得它作為生物感測器還能擁有極高的靈敏度及極低的偵測極限。此種結構也可解決長期困擾FET生物感測器的Debye length的問題，得以在高鹽濃度下偵測到生物分子，在這篇研究中也作了系統性的探討。為了驗證機制，我們挑選了miR-126的DNA序列作為待測物，並在感測器的閘極金電極上接上互補的DNA序列，藉以抓住目標待測物。確認感測器在DNA感測的極限達到1fM後，在TE buffer 調配的不同濃度miR-126、miR-21及miR-208a之RNA序列便接著作為感測物，直接量測RNA的結果也帶來可觀穩定的電荷上升趨勢。最後，晶片上也可透過植上aptamer序列來抓取其專一的CRP蛋白質，透過相同的量測方法，CRP在人體血清中的偵測極限為0.21 mg/L，相較於業界標準的機台極限0.2 mg/L來說相當接近。

In this research, the direct detection of DNA, RNA and proteins in physiological salt concentration by FET based biosensor has been investigated systematically. For the CVD biomarkers, miR-126, miR-21, miR-208a and CRP have been chosen. We have introduced a novel biosensor structure which can provide promising result with low detection limit and high resolution. The new biosensor structure with the electric-double layer structure can solve the Debye length problem which has been existed in FET sensors for years. The FET made by AlGaN/GaN HEMT having high transconductance gain, can significantly improve the S/N ratio and sensitivity. The sensor has shown its low detection limit of 1fM in DNA detection initially. Then, with the six, two and one mismatched base of DNA signal comparison, the specificity of the sensor is also proven. Furthermore, the three miR-126, miR-21 and miR208a RNA CVD biomarkers samples in TE buffer are also measured in different concentrations. The calibration curves of the three RNA sequences are all with appreciable increasing trend in total charge. Finally, the CRP quantitatively detection is also demonstrated in low concentrations and get the extremely low detection limit of 0.21 mg/L in human serum samples.

Chapter 1 Introduction 10

1.1 Motivation 10

Chapter 2 Literature Review 12

2.1 Cardiovascular disease (CVD) 12
2.1.1 C-reactive protein (CRP) as the CVD biomarker 14
2.1.2 miRNA as the CVD biomarker 16
2.2 Field effect transistor biosensor 17
2.2.1 AlGaN/GaN HEMT as a biosensor 19
2.3 Electric-double layer structure and Debye length 22
2.4 DNA detection method comparison 25
2.5 DNA thermodynamics 27
2.5.1 Melting temperature and Gibbs free energy 28
2.5.2 Binding ratio 32
Chapter 3 Experimental 33
3.1 HEMT fabrication 33
3.2 Aptamer immobilization 35
3.3 DNA probe immobilization 36
3.4 Measurement method 38
3.5 Measurement process 39

Chapter 4 results and discussion 42

4.1 Sensor mechanism illustration 42
4.2 miRNA-126 DNA sequences sensing 49
4.3 Probe specificity measurement 53
4.3.1 Six-base mismatch 53
4.3.2 Two-base mismatch 57
4.3.3 One-base mismatch 60
4.4 Sensor reuse experiment 63
4.5 miR-126 RNA sample detection 65
4.6 miR-21 RNA sample detection 68
4.7 miR-208a RNA sample detection 70
4.8 CRP samples detection 72

Chapter 5 Conclusion 75

Chapter 6 Reference 77

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