以熱泳效應提升電化學阻抗感測器靈敏度之研究與開發

Abstract

隨著科技進步，健康照護產業思維從病患照護轉為重視患病前的預防措施。由於結核病對公共健康存在長期威脅，本研究採用丙型干擾素檢驗 (Interferon-gamma release assays, IGRAs) 來作為篩檢結核病的檢測方法，相較於現今結核菌培養檢測的缺乏效率，此方法能增加診斷的效率。 本研究運用電化學阻抗量測低成本、易操作、體積小等特性，來作為生物感測器之傳感端，希望能讓其成為發展定點式照護感測器重要平台。過往的檢測方式是將生物細胞溶液流入生物晶片，藉待測物自然沉積至電極上與特定的受體(抗體)結合，將受體(抗體)與待測物(抗原)藉由特異性 (specificity) 結合所產生的狀態變化轉換成電訊號，所得的電訊號就成為生物晶片的檢測訊號。前述方法常面臨只有靠近電極表面之待測物有機會與抗體結合，因此浪費了不是位於電極表面的待測物，也因此造成濃度低之生物分子難以被偵測到，進而導致所得訊號的信雜比(S/N Ratio)不佳。 為提高電化學阻抗的靈敏度，此研究思考利用熱泳效應 (thermophoresis) 來將待測物推移到接近電極的位置，以提升生物晶片的信雜比。熱泳效應乃是流體中的微粒子在溫度梯度中移動的一種現象，其作法是在溶液中加入少量的聚乙二醇聚合物來驅動流體中的生物分子(抗原)，使抗原依溫度梯度向電極端移動，增加和抗體之鍵結效率。 再利用螢光強度在區域中的分布來判別其生物分子聚集情形，其成果及電化學阻抗值皆證明其方式較傳統方式能更有效聚集丙型干擾素 (Interferon-gamma, IFN-γ)，能使原本因濃度過低而無法偵測到的IFN-γ能夠被偵測，提高量測偵測極限 (limit of detection, LOD)。此研究也設計具加熱裝置之微流道晶片系統，使晶片能在機構中進行抗體固定化、抗原之聚集及電化學量測，因此乃能提升生物分子鍵結效率，縮短抗體與抗原的反應時間，來加速檢測流程。

With the advancement of science and technology, the focus of health care has gradually turned from patient treatment and care towards health enhancement and diseases prevention. Interferon-gamma release assays (IGRA) was adopted in this research to serve as an alternative of tuberculin skin test (TST) for the diagnosis of latent tuberculosis infection (LTBI) due to its high efficiency in identifying the infection of LTBI. Electrochemical impedance spectroscopy (EIS) biosensor was used to develop point-of-care (PoC) application platforms due to its characteristics such as low cost, simple instrumentation, fast response time, etc. To detect the spontaneous interaction between receptor (antibody) and analyte (antigen) in traditional biochips, specific binding variation was transformed into electrical signal which represented the detection signal of biochips. Only the analyte near the electrode surface has the opportunity to bind with the antibody, which not only leads to sample waste but also consumes precious testing time. All of which will make traditional biochips face limitations such as lower signal/noise ratio (S/N Ratio) in low analyte concentrations and long testing time, etc. To improve the sensitivity of EIS and the S/N Ratio of biochips, thermophoresis was adopted in this thesis to move the analyte to locations near the electrode surface. Thermophoresis is a phenomenon about the migration of particles with a temperature gradient, which was done by adding Polyethylene glycols (PEG) Polymer to drive molecule (antigen) motions through temperature gradient towards the EIS electrodes in order to increase the binding rate. By observing the fluorescence from the capture probes bound to the antigens and the EIS results, Interferon-gamma (IFN-γ) was found to indeed accumulate near the electrode as lower concentration and improved detection limit (LOD) were observed. In this thesis, we developed a microfluidic biochip system which can execute binding steps, accumulate antigen by steady temperature gradient and enhance the sensitivity of electrochemical measurement while reducing the binding time.