LAUSR

Currently, the use of electrical readout methods with lab automation tools for investigation of microtissue spheroids, such as robotic arms, is hindered by the cable connections that are required to interrogate the on-chip-integrated electrodes. To overcome this limitation, we developed a wireless sensor scheme, which subsequently has been used to detect the size variation of microtissues during long-term culturing and drug exposure assays. The sensor system included an interroga-tion board, which featured an inductor-capacitor (LC) readout circuit and the tissue culture platform with integrated split-ring sensors. The magnetic coupling between the LC circuit and the sensors enabled the interrogation of the on-chip sen-sors without any wire connection to the culture platform. By optimizing the sensor dimensions and the LC resonance fre-quencies, we were able to avoid cross talk between neighboring sensors. We integrated 12 tissue compartments on a stand-ard microscopy slide at a sensor-to-sensor pitch of 9 mm, which is in accordance with standard 96 well-plate dimensions. As proof-of-concept experiment for the developed system, we monitored continuously during more than four days the growth inhibition of colon-cancer microtissue spheroids that had been exposed to different concentration of doxorubicin, a chemotherapeutic compound. The stability of the measurements during long-term culturing and the compatibility of the sensor scheme with standard lab equipment offers great potential for automated electrical microtissue spheroid char-acterization.