A novel microfluidic impedance assay for monitoring endothelin-induced cardiomyocyte hypertrophy

Cardiac hypertrophy is an established and independent risk factor for the development of heart failure and sudden cardiac death. At the level of individual cardiac myocytes (heart muscle cells), the cell morphology alters (increase in cell size and myofibrillar re-organization) and protein synthesis is activated. In this paper, a novel cardiomyocyte-based impedance sensing system with the assistance of dielectrophoresis cell concentration is reported to monitor the dynamic process of endothelin-1-induced cardiomyocyte hypertrophy. A dielectrophoresis (DEP) microfluidic device is fabricated capable of concentrating cells from a dilute sample to form a confluent cell monolayer on the surface of microelectrodes. This device can increase the sensitivity of the impedance system and also has the potential to reduce the time for detection by a significant factor. To examine the feasibility of this impedance sensing system, cardiomyocytes are treated with endothelin-1 (ET-1), a known hypertrophic agent. ET-1 induces a continuous rise in cardiomyocyte impedance, which we interpret as strengthening of cellular attachments to the surface substrate. An equivalent circuit model is introduced to fit the impedance spectrum to fully understand the impedance sensing system.