Maestro pro

A Maestro Pro (Axion Biosystems) multi-electrode array (MEA) system was used to measure the spontaneous firing of neurons (Trombetta-Lima et al., 2021 (link)). We coated CytoView MEA 48 plates (Axion Biosystems, M768-tMEA-48W) containing sixteen embedded electrodes per well with PO/LM/FN. The coating solution was aspirated, and the wells were left to dry for 30 min. Dissociated NCC spheroids (day 16) were seeded in high-concentration LM (10 μM/ml) drops (5 µl/drop) into the center of the MEA well. The cells were incubated (60 min, 37 °C) before adding AN medium. Repeated recordings were made every 10 days for 15 min. The MEA plate was inserted into the MEA Maestro (37C, 5% CO₂) for spike detection. Axion AxIS Software recorded raw voltage data and detected spikes for rate analysis.

Measurement of impedance and spontaneous extracellular field potentials were acquired at 37 °C under a 5% CO₂ atmosphere using an MEA system (Maestro Pro, Axion Biosystems, Atlanta, GA, USA). After setting MEA plates, impedance of all electrodes was tracked and obtained for 3 min. Then, spontaneous activities were recorded for 5 min at a sampling rate of 10 kHz/channel. All signals were stored on a personal computer.
After cultured DRG neurons for 14 days, four representative anticancer drugs were administered to the cultures at two different concentrations (low and high) each: paclitaxel at 0.1 µM (n = 4 wells) and 1 µM (n = 5 wells), vincristine at 0.003 µM (n = 4 wells) and 0.03 µM (n = 5 wells), oxaliplatin at 10 µM (n = 4 wells) and 100 µM (n = 5 wells), and bortezomib at 0.001 µM (n = 4 wells) and 0.01 µM (n = 5 wells). Sucrose (10 µM) was added as a negative drug (n = 5 wells), and DMSO (0.1%) as a control drug to the cultures (n = 5 wells). The drug exposure lasted for 168 h at 37 °C. Before drug exposure (before) and 24 h, 72 h, and 168 h after exposure, measurements of impedance and spontaneous activities were performed.

The neural signal in the 2D MEA was acquired by the Maestro Pro commercial system (Axion Biosystems, Inc.). The hHO was seeded on 6-well CytoView MEA plates containing 64 electrodes coated with PLL-laminin. The hHO was seeded in advance for 2 weeks for adhesion before recording neural activities. During this period, hHOs were cultured in the differentiation medium 2 supplemented with BDNF and GDNF. Before recording spontaneous spikes, the Axion instrument was allowed to stabilize the environment for 30 min without any stimulation. The AxIS Navigator performed spike waveform and network bursts. Data were analyzed through the companion software NeuralMetric Tool.
Signal acquisition by the mMPC was performed on the OmniPlex Neural Recording Data Acquisition System (Plexon Inc.). Our mMPC was connected to the head stage of the system via an FFC adapter. The Plexon system recorded data from 32 electrodes simultaneously, with a sampling rate of 40 kHz. The threshold for spike detection was set above 5 standard deviations from the average noise level, with a bandpass filter between 200 and 6000 Hz. The window length to isolate spikes was 800 µs. The neural spike sorting, analysis, and result presentation were done in Plexon companion softwares, Offline Sorter, and NeuroExplorer.