A microchip integrating cell array positioning with in situ single-cell impedance measurement

Abstract

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.

Microfluidic device embedding electrodes for dielectrophoretic manipulation of cells‐A review

“…This kind of method by using dielectrophoresis‐assisted clinical diagnosis has been deeply studied and applied by many researchers .…”

Micro electrical impedance spectroscopy on a needle for ex vivo discrimination between human normal and cancer renal tissues

“…7, an equivalent circuit was proposed based on the lEoN structure on the condition that the lEoN was immersed in the bio-tissues. [28][29][30][31][32][33][34] The total sensor output is a combination of the resistance (R) and capacitance (C) of parylene C and tissue samples, double layer capacitance, and constant phase element (CPE).…”

Ex vivo characterization of age-associated impedance changes of single vascular endothelial cells using micro electrical impedance spectroscopy with a cell trap

“…26 The solution in the cell-flowing channel is expressed in terms of resistance (R sol ), which is connected in series with a single constant phase element (CPE) corresponding to the double layer impedance. 25,27 R seal represents seal resistance bypassing the trapped cell. 25,28 Parasitic capacitance (C p ) is also included because a parasitic effect exists in a microdevice and measurement system.…”

“…25,28 Parasitic capacitance (C p ) is also included because a parasitic effect exists in a microdevice and measurement system. 25,29 The best-fitting parameters from 1 kHz to 1 MHz were extracted using non-linear least squares fitting in the Gamry Analyst software. Initially, the impedance data without cells were used to calculate C p .…”

“…Thus, cytoplasm resistance (R cyto ) and membrane capacitance (C mem ) values were extracted by fitting an electrical equivalent circuit to the data of the sensor output. A model of a cell that has a contact with the electrodes in medium 25 was employed in the equivalent circuit to estimate R cyto and C mem , as shown in Fig. 4.…”