Guo Xiaoliang, Zhu Rong, Zong Xianli
State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instruments, Tsinghua University, Beijing, China.
Analyst. 2015 Oct 7;140(19):6571-8. doi: 10.1039/c5an01193k. Epub 2015 Aug 18.
This paper presents a novel microarray chip integrating cell positioning with in situ, real-time and long-time impedance measurement on a single cell. The microchip integrates a plurality of quadrupole-electrode units (termed positioning electrodes) patterned into an array with pairs of planar electrodes (termed measuring electrodes) located at the centers of each quadrupole-electrode unit. The positioning electrodes are utilized to trap and position living cells onto the measuring electrodes based on negative dielectrophoresis (nDEP), while the measuring electrodes are used to measure impedances of the trapped single cells. Each measuring electrode has a small footprint area of 7 × 7 μm(2) to ensure inhabiting only one single cell on it. However, the electrode with a small surface area has a low double-layer capacitance when it is immersed in a liquid solution, thus generating a large double-layer impedance, which reduces the sensitivity for impedance measurement on the single cell. To enlarge the effective surface areas of the measuring electrodes, a novel surface-modification process is proposed to controllably construct gold nanostructures on the surfaces of the measuring electrodes while the positioning electrodes are unstained. The double layer capacitances of the modified electrodes are increased by about one order after surface-modification. The developed microchip is used to monitor the adhering behavior of a single HeLa cell by measuring its impedance spectra in real time. The measured impedance is analyzed and used to extract cellular electrical parameters, which demonstrated that the cell compresses the electrical double layer in the process of adherence and adheres onto the measuring electrodes after 4-5 hours.
本文提出了一种新型微阵列芯片，该芯片将细胞定位与单个细胞的原位、实时和长时间阻抗测量集成在一起。该微芯片集成了多个四极电极单元（称为定位电极），这些单元被图案化为阵列，在每个四极电极单元的中心位置有一对平面电极（称为测量电极）。定位电极用于基于负介电泳（nDEP）将活细胞捕获并定位到测量电极上，而测量电极则用于测量捕获的单个细胞的阻抗。每个测量电极的占地面积很小，为7×7μm²，以确保其上仅栖息一个单细胞。然而，当电极浸入液体溶液中时，表面积小的电极双层电容较低，从而产生较大的双层阻抗，这降低了对单细胞阻抗测量的灵敏度。为了扩大测量电极的有效表面积，提出了一种新颖的表面改性工艺，在定位电极未受影响的情况下，可控地在测量电极表面构建金纳米结构。表面改性后，改性电极的双层电容增加了约一个数量级。所开发的微芯片用于通过实时测量其阻抗谱来监测单个HeLa细胞的粘附行为。对测量的阻抗进行分析并用于提取细胞电参数，结果表明细胞在粘附过程中压缩了双电层，并在4-5小时后粘附到测量电极上。
