| 摘要: | 低濃度核酸檢測已廣泛應用於疾病的診斷及治療後，藉此改善病人之治療方式與進程，而最常用於核酸檢測的方式為即時檢測聚合酶反應及微陣列基因序列，但其成本較高且相對耗時。少數研究已經開始採用矽奈米線場效電晶體元件，因其具有高靈敏性、即時檢測和體積小且操作等優勢，因此被視為具有淺力的核酸檢測平台，甚至作為定點照護檢驗（POCT）工具。
雖然場校電晶體具有即時檢測樣品的優勢，仍需要考量核酸擴散至檢測表面的反應時間。以往一般利用場校電晶體檢測核酸的研究中，核酸在擴散與反應的過程中並未受到額外電場的影響下，目標核酸（Target oligonucleotide）於擴散中主要受到溶液流體流動的convection以及Brownian diffusion的影響。當目標物進一步逐漸移動至探針表面進行結合時，過程中擴散所需要花費的時間，比目標核酸與核酸探針雜交結合反應的時間長，尤其在樣品中核酸濃度很低時。所以若要縮短目標核酸與探針雜交的反應平衡達到檢測時間縮短，加速核酸主要速率限制步驟的擴散反應速率將會是主導整體核酸檢測時間的關鍵。
本研究利用多晶矽奈米線場效應電晶體（poly-SiNW FET）作為生物感測器，以oligonucleotide為探針來辨識具有互補性的目標DNA，於liquid gate施加負電壓於反應槽，形成電場驅動核酸加速至表面，以期待縮短核酸擴散至探針表面的時間。研究探討調整不同閘極負電壓、注射流速及探針固定化接枝時間等，期望找出合適之電場參數作為加速FETs應用於核酸檢測時間之條件。
研究首先以X射線光電子能譜儀(XPS)、原子力顯微鏡(AFM) 探針已成功改植於晶片上。利用FET結合調整閘極電壓、注射流速，發現在低注射流速下，以及–1 V產生的電場效應下目標DNA能穩定擴散，將反應平衡時間從約60分鐘縮短至20分鐘。接著改變探針固定化時間，以有助於提高表面固定化量，並透過FET施加電場後目標DNA與探針碰撞機率增加，其訊號差異性有顯著提升，在不同檢測濃度下街保有優越性能，反應時間仍可與未施加電壓提早10 分鐘達到檢測終點。
以上研究為首次於場效電晶體檢測加入設備中探討外加電場對檢測時間加速的結果，成功的結果可以看見外加電場於奈米場效應電晶體於檢測低濃度核酸的潛力。
;Ultra-low concentration nucleic acid detection has been widely applied in the diagnosis and treatment of diseases to improve patient treatment strategies and outcomes. Real-time polymerase chain reaction (PCR) and next-generation gene sequencing are the most common methods for nucleic acid detection, while their high cost and relatively lengthy processing times present challenges. Some studies have started to adopt silicon nanowire field-effect transistor (SiNW FET) devices due to their high sensitivity, real-time detection, small size, and ease of operation. Therefore, the SiNW FET devices are promising platforms for nucleic acid detection, including the potential use as Point-of-Care Testing (POCT) equipment.
Despite the advantages of real-time sample detection offered by FETs, the reaction time for nucleic acid diffusion to the detection surface remains a critical consideration. In previous studies using SiNW FETs for nucleic acid detection, the diffusion and reaction of the target oligonucleotide were primarily influenced by fluid flow convection and Brownian diffusion without the additional influence of an external force field, such as an electric field. As the target molecule gradually moves towards the probe surface for binding, the time required for diffusion becomes a limiting factor, especially when nucleic acid concentrations in the sample are low. Therefore, speeding up nucleic acid detection lies in accelerating the diffusion reaction rate of the primary rate-limiting step during the hybridization of target nucleic acids with probes.
This study used polycrystalline silicon nanowire field effect transistors (poly-SiNW FET) as biosensors, with oligonucleotides as probes to recognize complementary target DNA. A negative voltage was applied to the liquid gate used for detection to create an electric field that drives nucleic acids to the surface. This attempt to shorten the diffusion from nucleic acids to the probe surface. The research involved adjusting the gate voltages, injection flow rates, and probe immobilization times to find suitable electric field parameters for accelerating FETs in nucleic acid detection.
X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) confirm the successful immobilization of probes on the chip. By combining FET with adjusted gate voltage and injection flow rate, it was found that at a low injection flow rate and a -1 V electric field, the target DNA can stably diffuse, reducing the equilibrium time from approximately 60 minutes to 20 minutes. Further changes in probe immobilization time enhance surface immobilization, and applying an electric field via FET increases the collision probability between target DNA and probes. The signal differences significantly improve, maintaining superior performance at different detection concentrations, and the reaction time still achieves the detection endpoint 10 minutes earlier than without applying voltage.
This study first explores the results of applying an external electric field to accelerate detection time in field-effect transistors. The successful outcomes highlight the potential of an external electric field in accelerating the detection of low-concentration nucleic acids in nanowire field-effect transistors. |
