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Measurement of Live Synaptic Physiology with Multielectrode Arrays (MEAs)
1. Prepare MEAs for cell culture.
- Clean the surface of each MEA with 1 mL of detergent for 1 h. Rinse with sterile deionized (DI) water, rinse with 70% ethanol to sterilize, and then air dry in a biosafety cabinet under UV light.
NOTE: MEAs can be stored in DI water at 4 °C under sterile conditions until use.
- Prepare a 0.5 mg/mL solution of poly-ornithine (PLO) by dissolving 50 mg of PLO into 100 mL of boric acid buffer. Coat the surface of each MEA with 1 mL of PLO to render it hydrophilic and incubate at 37 °C for a minimum of 4 h. Remove the PLO and wash the surface with DI water.
- Dilute extracellular matrix (ECM) coating solution with basal (DMEM/F12) media to prepare a 1 mg/mL stock solution. For a working solution, resuspend 3 mL of ECM stock into 33 mL of pre-chilled DMEM/F12 media, bringing the total volume to 36 mL for a concentration of 80 µg/mL.
- Add 1 mL of ECM working solution to each MEA and incubate at 37 °C for a minimum of 4 h.
- Remove the ECM and place the spheres in 1.5 mL of media on a MEA surface, ensuring that the spheres are positioned on top of the electrode array (Figures 1A, 1A'). Allow the media to adhere for 2 days. Change half of the media every 2–3 days (or more often if needed), ensuring that the spheres are not disturbed.
NOTE: The addition of growth factors may improve culture survival and maturation.
2. Measure the electrical activity of neural spheres.
- Set up a multielectrode array (MEA) system with a temperature-controlled headstage. Create a software program with a 5 Hz high-pass filter, a 200 Hz low-pass filter, and a spike threshold of 5x standard deviation (SD).
- Place the MEA on headstage and record spontaneous electrical activity (Figure 1B, B'). Save raw data, including spike frequency and amplitude, for statistical analysis.
NOTE: A perfusion system may be utilized with the MEA to add pharmacological agents or to increase the flow of fresh media for long-term recording. As desired, additional post-processing of spikes may be performed.
