Mea2100 lite system

MEAs (Multi Channel Systems, 60MEA200/10iR-Ti) consist of 59 titanium nitride (TiN) working electrodes with a diameter of 10 μm with 200 μm spacing between electrodes and one internal reference electrode. Prior to recording, MEAs were treated with oxygen plasma for 30 seconds using a PX-500 Plasma System (March Instruments), 100 μg/mL of poly-D-lysine overnight (Sigma, P0899), and 10 μg/mL Laminin (Sigma, L2020) for 2h prior to culture of primary neurons. For recording, culture medium was removed and 1 mL of warmed MEA recording solution^{85 (link),86 (link)} was added to each MEA. Each culture was allowed to equilibrate with the MEA solution for 5 minutes in the 37°C incubator before recording. Recordings were conducted with a MEA2100-Lite-System (Multi Channel Systems) that was maintained at 37°C using the TC02 temperature controller (Multi Channel Systems). The Multi Channel Experimenter software (Multi Channel Systems) was used to record the extracellular potential at each electrode for 5 minutes using a sampling rate of 20 kHz. After recording, MEA recording solution was removed and the conditioned cell culture medium was returned to the MEA.

Organoid electrical activity was measured using an MEA2100-lite system with TC01 temperature control (Multi Channel Systems), heated to 37°C. Recordings were made for 5–10 min at a frequency of 10 kHz using Multi Channel Experimenter software. Data were processed using Multi Channel Analyzer software. Raw electrode recordings were filtered sequentially with a 200 Hz second-order Butterworth high-pass filter, then a 3 kHz second-order Butterworth low-pass filter. Spikes were picked using a threshold of 5 SDs below mean voltage for each electrode.