Microfluidic contactless conductivity cytometer for electrical cell sensing and counting

Abstract

The microfluidic cytometer has recently attracted increasing attention in cell sensing and counting due to its advantages of high-speed measurement, small sampling size and being cost effective. Up to now, the conventional microfluidic cytometer has usually used expensive microelectrodes directly in contact with a cell suspension to measure the changes in electrical signals. In this paper, we introduce a novel approach to construct an integrated microfluidic contactless conductivity cytometer for non-invasive analysis of samples with a small number of cells. The microfluidic chip is composed of a polydimethylsiloxane (PDMS) plate with a narrow microchannel on the top, a 100 μm thick glass plate in the middle and a glass substrate containing indium tin oxide (ITO) detecting electrodes on the bottom. This contactless measurement approach avoids direct contact between the detection buffer and the ITO electrodes, allowing the electrodes to be easily reused and lowering the cost of the device. When cells flow through a narrow microfluidic channel which is a little larger than the tested cell size, electrical signals are detected by a capacitively coupled contactless conductivity detection (C4D) system. Furthermore, human breast cancer (MCF-7) cells and hypertrophic cardiomyocytes (HCM) were used to successfully demonstrate the feasibility of the microfluidic contactless conductivity sensor for counting and detecting cells. Consequently, the designed microfluidic cytometer is cost-effective, easy-to-use and label-free. It is reasonable to expect that this microfluidic cytometer can become a promising tool for label-free cell counting and point-of-care clinical diagnosis in the developing world.