miRNA 已被證實在多種癌症以及心血管疾病上是極具潛力的生物標記，具有高敏感度、高特異性的性質。然而，因為 miRNA 在體內極低的濃度使它的檢測方式與發展具有很大的限制。現今常見miRNA檢測方式為使用聚合酶連鎖反應(PCR)放大miRNA濃度來做檢測，這樣的方式具又費時且無法直接檢測原始濃度的缺點。因此，本研究擬設計一場效電晶體(FET)生物感測器來檢測 miRNA，透過FET放大訊號的特性替代PCR反應。
為了設計出優良的miRNA電晶體(FET)生物感測器，本研究使用不同鍍金方式、不同溫度以及不同水溶液觀察電訊號的變化，發現水中離子會依循布朗運動的機制，而降低布朗運動則能有效提高電訊號的穩定程度。透過不同濃度的DNA探針接枝，觀察感測器量測miRNA所表現的敏感度與感測範圍。並透過上述實驗選出最佳條件，製備具高敏感度、高穩定度和大檢測範圍的 miRNA FET生物感測器。
最後，以錯誤序列的樣品檢測實驗證明感測器的高選擇性。用ELISA 螢光訊號與FET電訊號的比較顯示FET生物感測器能檢測的濃度極限更低。證明miRNA FET生物感測器能直接量測miRNA原始濃度而不需透過PCR放大濃度，能有效解決現今 miRNA 檢測所面對的問題。

Micro RNA (miRNA) has been proven as highly potent biomarkers for variety of cancers and cardiovascular diseases. Typically detection methods of miRNA use polymerase chain reaction (PCR) to amplify the miRNA concentration in the test sample. This method has the disadvantage of being time-consuming and it is unable to directly detect the original miRNA concentration. Therefore, this study intends to design a FET biosensor to detect miRNA.
In order to design a stable and highly sensitive miRNA FET biosensor, this study used different metal deposition techniques to form sensing electrodes and observed sensor response in different temperatures and aqueous solutions to evaluate the fluctuation of the electrical signal, and found that the ions in the solution will follow the Brownian motion and cause fluctuations. While the Brownian motion reduces, the stability of the electrical signal will be improved. Then we used different concentrations of ssDNA probe to functionalize the sensor chip in order to detect target miRNA concentration, to compare the dynamic range and sensitivity. The optimization can help us to make a miRNA FET biosensor with high sensitivity, high stability and large detection range.
Additionally, the experiments using miRNA with mismatched nucleotide sequence from the target, demonstrate the high selectivity feature of the sensor. Comparison of ELISA based fluorescent signal with FET sensor signal shows that FET biosensors can achieve better detection limits. These data proved that the miRNA FET biosensor can directly measure the original concentration of miRNA without amplifying the concentration using PCR, which can effectively solve the problems faced by miRNA detection at the present time.

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