Monitoring of 3D multi-cellular spheroids in hanging drop networks through in-situ impedance spectroscopy

We present the integration of electrical impedance spectroscopy (EIS) into a microfluidic network of hanging drops, in which spherical microtissues can be formed and cultured over time. EIS offers continuous monitoring of the drop volume and media conductivity and in-situ measurements of spheroid growth for different culturing conditions. The integration has been achieved by using a hybrid fabrication method, in which electrode modules on glass substrates were embedded into a microfluidic PDMS structure. The measurement results show robust drop volume control and, for the first time, size determination of human colon carcinoma spheroids directly inside a hanging drop