Electrical impedance spectroscopy of single cells in hydrodynamic traps

This paper presents a new design of a microfluidic device combining hydrodynamic trapping and impedance spectroscopy measurements of single cells. Four microelectrodes integrated within cell traps enable impedance measurements in varying electrode pair configurations. To improve the impedance response of the microelectrodes, a modification using electrodeposition of a conductive polymer was applied. A considerable decrease of impedance magnitude was observed, and thus a significant enhancement of the useful frequency range was obtained. After electrode modification, the 12 × 22 μm² electrodes were sensitive for frequencies ranging from 10 KHz to 2-5 MHz. Impedance measurements were carried out on single mouse oocytes with and without the surrounding glycoprotein matrix, called zona pellucida. Higher impedance values were obtained for zona pellucida-free than for zona pellucida-intact oocytes, reflecting the known high electrical conductivity of the zona pellucida.