細胞阻抗分析被廣泛地應用於監測生物與藥物反應，而本研究利用微影、電鑄技術製備一個高靈敏度、高深寬比的立體指叉式微電極於聚醯亞胺軟式電路板上，用以細胞檢測。先經由立體有限元素方法的模擬，來比較立體與平面指叉電極的效能，來決定電極設計，用乳膠微粒子浸泡於細胞培養液(DMEM)來模擬細胞，免除活細胞在代謝、生長、凋亡對阻抗量測的影響，避免這些生化現象對電極靈敏度的干擾，捕捉不同數量的微粒子於電極上進行阻抗量測。立體指叉式微電極可使微粒子排列於電極間隙，而不在電極上，可避免由微粒子位置所造成的干擾。以量測的結果來看，立體指叉式微電極的靈敏度至少比平面指叉式微電極高五倍，且阻抗趨勢隨著微粒子數量增加而增加，與等效電路模擬結果相符。最後，利用500 kHz處之阻抗與微粒子數量之回歸線(拋物線)來預測微粒子數量，69顆微粒子的阻抗量測值為1269 Ω，用回歸線預測結果為68顆，準確率為98.6%。
經過量測微粒子證明立體指叉式微電極有較優異的靈敏度後，在本研究中也用此電極當成多細胞電阻抗傳感器，藉此量測分析細胞的電特性。細胞電特性，如細胞膜電容與細胞質電阻，可提供許多訊息來研究細胞膜與細胞質所發生的變化，且不需複雜的生化檢測。本研究提供一個分析方法以此多細胞電阻抗傳感器配合等效電路來提取細胞電特性，子宮頸癌細胞可快速、簡單地被此立體指叉式微電極與SU-8做成的柱子捕捉並排列於電極間隙，無細胞定位上的困擾。實驗結果證明了等效電路的準確性與有效性，且顯示了本傳感器在460 kHz附近對子宮頸癌細胞有最佳靈敏度；藉由所呈現的細胞電特性提取方法，成功地從52顆子宮頸癌細胞中得到細胞膜電容與細胞直電阻，並且將其值代入等效電路模型中，來模擬預測15、29、78、98顆子宮頸癌細胞的電阻抗，模擬預測的阻抗與實際量測值之間最大誤差在阻抗振幅只有3.06%，而在相位只有4.67%。這證明了可由細胞電特性來辨別細胞數量，也同時證明了用多細胞傳感器與等效電路來求得細胞電特性的可行性。

Cell impedance analysis is widely used for monitoring biological and medical reactions. In this study, a highly sensitive three-dimensional (3D) interdigitated microelectrode (IME) with a high aspect ratio on a polyimide (PI) flexible substrate was fabricated for microparticles detection using electroforming and lithography technology. 3D finite element simulations were performed to compare the performance of the 3D IME (in terms of sensitivity and signal-to-noise ratio) to that of a planar IME for microparticles in the sensing area. Various quantities of microparticles were captured in Dulbecco’s modified Eagle medium (DMEM) and their impedances were measured. With the 3D IME, the microparticles were arranged in the gap, not on the electrode, avoiding the noise due to particle position. For the maximum particle quantities, the results show that the 3D IME has at least 5-fold higher sensitivity than that of the planar IME. The trends of impedance magnitude and phase due to particle quantity were verified using the equivalent circuit model (ECM). The impedance (1269 Ω) of 69 microparticles was used to estimate the particle quantity (68 microparticles) with 98.6% accuracy using a parabolic regression curve at 500 kHz.
After proofing the advantage of 3D IME on sensitivity, this study also proposes the use of electric cell-substrate impedance sensing (ECIS) to detect the electrical properties of cells by the 3D-IME. The membrane capacitance (Cc) and cytoplasm resistance (Rc) can provide the information required to investigate changes in the membrane and cytoplasm without the need for complex chemical biochemical detection. The proposed method was used to analyze the electrical properties of a multiple-cells impedance biosensor (MCIB) and the application of an ECM by using the 3D IME. HeLa cells were quickly captured at the gap of the electrodes without cellular localization because of the presence of SU-8 columns and the 3D IME. In order to understand the impedance measured with the 3D IME, the ECM was used to analyze the impedance spectrum. The experimental results validated the accuracy and validity of the model, and the sensor with the best sensitivity for HeLa cells was found at 460 kHz. The normalized Rc and Cc were calculated by measuring 52 HeLa cells. The simulation results using Rc, Cc and the ECM successfully forecasted the impedance magnitudes and phases for 15, 29, 78, and 98 HeLa cells. The comparison of the simulation results and the measurement results showed that the maximum average errors in magnitude and phase were only 3.06% and 4.67%, respectively, which suggests that the number of HeLa cells can be classified based on their electrical properties. It also validates the feasibility for using the proposed multiple-cells sensor and the ECM to evaluate the cellular electrical properties.

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