How to Seed Cells

How to Prepare the Plate and Seed Cells

This is a short tutorial describing how to handle MaxWell plates and prepare them for cell seeding. Please make sure to also read the official MaxWell protocols carefully. The procedures described here are recommendations based on empirical experience across many different projects encountered at the facility.

There is no guarantee that these protocols will work optimally for every cell type, and additional optimization steps may be required to identify the best conditions for your specific cells.

1. Prepare the Plates

For 6-well plates

If you are using a 6-well plate, the plate must first be pre-treated and sterilized.

Pre-treatment

Pre-treatment with 1% Terg-a-zyme increases the hydrophilicity of the sensor surface.

  • Prepare a 1% Terg-a-zyme solution in sterile ddH₂O.
  • Fill the chips and incubate for 2–3 hours (up to overnight) at room temperature.
  • Thoroughly rinse the plates with sterile ddH₂O 3–4 times using 2–3 mL per rinse.

Sterilization

  • Spray all external surfaces of the plate thoroughly with 70% ethanol.
  • Place the plate in a sterile environment (cell culture hood).
  • Fill all wells and surrounding areas with cell-culture-grade 70% ethanol.

Make sure the gold pins at the bottom of the plate remain as dry as possible, as they corrode easily and corrosion will negatively affect recordings.

  • Incubate with 70% ethanol for at least 30 minutes under the hood.
  • Do not use UV light, as this can reduce the longevity of the electronics.

After sterilization:

  • Rinse the plates with sterile ddH₂O 3–4 times.
  • Allow the plates to dry under the hood until first use.

For 24-well plates

MaxWell ships 24-well plates pre-sterilized, so you can proceed directly to the pre-conditioning step.

If you are re-using a plate (cell-free), follow the same pre-treatment and sterilization steps described for 6-well plates.

2. Pre-conditioning

Pre-conditioning is recommended, especially before first use.

  • Incubate the sterilized plates with sterile culture media in the incubator for 1–2 days.
  • No washing step is required before coating.

3. Coating

Before seeding, the sensor surface must be coated to promote cell adhesion. This is particularly important for HD-MEA sensors, as their surface is smoother than standard cell-culture plastic.

We recommend starting with coating protocols that are already known to work for your cell type, especially if you have experience culturing them on glass coverslips.

If you do not normally coat surfaces, the following is a recommended starting protocol:

  • Coat with Poly-D-Lysine (PDL) or Poly-L-Lysine (PLL) overnight in the incubator.
  • Follow with Laminin (20 ng/µL) coating for 1 hour in the incubator.
  • Wash with ddH₂O or PBS between coating steps.

To conserve Laminin, you may coat only the sensor area:

  • Ensure the entire sensor area is covered (approximately 50 µL).
  • It is generally recommended not to let the surface dry after coating.

4. Seeding Cells

After coating, the plates are ready for cell seeding. Typical seeding densities: - 50,000–150,000 cells per well on the sensor area

Note

We strongly recommend performing a pilot experiment using different cell numbers and concentrations.

Key considerations:

  • The sensor area is covered with approximately 50 µL of solution.
  • Concentrate your cell suspension accordingly.
  • After seeding, place the plate in the incubator for 1 hour.
    • Do not exceed 1 hour, as evaporation of the 50 µL can occur.

After incubation, carefully fill the wells:

  • 24-well plates: ~500–600 µL per well
  • 6-well plates: 1–1.5 mL per well

Proceed with your normal cell culture routine.

Tips and Tricks

  • Never touch the sensor area with pipette tips, as this may damage the electronic components.
    When aspirating liquid, place the aspirator carefully at the corner of the sensor area and slightly tilt the plate.

  • When placing 50 µL of solution on the sensor area, make sure the surrounding area is dry.
    Any liquid connection to wet regions outside the sensor area will cause the droplet to spread and may prevent full coverage of the sensor.

Always verify that you can see a distinct liquid bubble over the sensor area. This is critical for successful seeding, as spreading will cause cells to distribute outside the sensor instead of settling on it. - If you notice that the liquid is spreading too much, try reducing the volume slightly (e.g., to 40 µL).
Alternatively, you can try to absorb excess liquid from the corners of the sensor area using a sterile tissue or pipette tip (without touching the sensor surface).