In a microfluidic impedance cytometer with co-planar microelectrodes, unusual “double peak” features were observed in the reactive component of the electrical signatures from individual red blood cells. This phenomenon was observed only at specific frequencies (400 - 800 kHz) and its occurrence was facilitated by the microelectrode geometry. One of the most signifcant observations of this study was the high sensitivity of the features in the “double peak” profile to changes in cell membrane capacitance (CMC). This was demonstrated by accurately distinguishing populations of normal and glutaraldehyde treated erythrocytes based on variations in their CMC, indicating a drastic decrease in the CMC of treated cells. This double peak effect was further used to identify and classify discrete cell populations within a mixture of white blood cells. This study is an improvement over conventional approaches of measuring CMC via impedance flow cytometry by enabling the measurement of both cell size and cell membrane properties at a single frequency rather than using multiple frequencies. Using a single frequency significantly simplifies the system and reduces the associated costs.
This work was carried out by Karthik Mahesh, Manoj Varma and Prosenjit Sen as part of a joint effort between the ‘Microfluidic Devices and Heterogenous Systems’ lab and the ‘Complex Systems and Molecular Sensors’ lab. It was published in ‘Lab on a Chip’ in October 2020.
For more details, please visit: https://doi.org/10.1039/D0LC00744G