Department of Electrical and Computer Engineering, University of Manitoba, Winnipeg, Manitoba R3T 5V6, Canada.
Lab Chip. 2009 Dec 7;9(23):3406-12. doi: 10.1039/b908974h. Epub 2009 Oct 2.
In biomedical applications ranging from the study of pathogen invasion to drug efficacy assays, there is a growing need to develop minimally invasive techniques for single-cell analysis. This has inspired researchers to develop optical, electrical, microelectromechanical and microfluidic devices for exploring phenomena at the single-cell level. In this work, we demonstrate an electrical approach for single-cell analysis wherein a 1.6 GHz microwave interferometer detects the capacitance changes (DeltaC) produced by single cells flowing past a coplanar interdigitated electrode pair. The experimental and simulated capacitance changes generated by yeast cells are in close agreement. By using the capacitance changes of uniform polystyrene spheres (diameter = 5.7 microm) for calibration purposes, we demonstrate a 0.65 aF sensitivity in a 10 ms response time. Using an RC circuit, a low frequency sinusoidal potential is simultaneously superimposed on the electrode pair to generate a dielectrophoretic force that translates cells. Specifically, when yeast cells suspended in a solution of 90 ppm NaCl in deionized water are exposed to 10 kHz and 3 MHz potentials (ranging from 1-3 V(pp)), they experience negative and positive dielectrophoresis, respectively. The corresponding changes in cell elevation above the interdigitated electrodes are detected using the asymmetry of the capacitance signature produced by the cell. Cell elevation changes can be detected in less than 80 ms. The minimum detectable change in elevation is estimated to be 0.22 microm. This approach will have applications in rapid single-cell dielectrophoretic analysis, and may also prove useful in conjunction with impedance spectroscopy.
在从病原体入侵研究到药物功效分析等广泛的生物医学应用中，人们越来越需要开发微创技术来进行单细胞分析。这激发了研究人员开发光学、电气、微机电和微流控设备，以探索单细胞水平的现象。在这项工作中，我们展示了一种用于单细胞分析的电气方法，其中 1.6GHz 微波干涉仪检测流过共面叉指电极对的单个细胞产生的电容变化 (ΔC)。实验和模拟产生的酵母细胞的电容变化非常吻合。通过使用均匀聚苯乙烯球（直径 = 5.7μm）的电容变化进行校准目的，我们在 10ms 的响应时间内实现了 0.65aF 的灵敏度。使用 RC 电路，将低频正弦电势同时叠加在电极对上，以产生介电泳力来平移细胞。具体来说，当悬浮在去离子水中 90ppmNaCl 溶液中的酵母细胞暴露于 10kHz 和 3MHz 电势（范围为 1-3V(pp)）时，它们分别经历负介电泳和正介电泳。使用细胞产生的电容特征的不对称性检测细胞在叉指电极上方的升高变化。细胞升高变化可在不到 80ms 的时间内检测到。估计最小可检测的升高变化为 0.22μm。这种方法将在快速单细胞介电泳分析中得到应用，并且与阻抗谱结合使用也可能很有用。
