What is the edge effect?
When using multiwell plates, you’ll likely encounter the edge effect. It happens when the measurements from the outer wells are widely different from the ones toward the center of the plate. It affects the assay’s repeatability and reproducibility.
The edge effects can appear in both biochemical and cell-based assays. They can be due to various factors. As such, labs often employ solutions to prevent their occurrence.
If you’re experiencing it and looking for solutions, our guide can help. Read on to learn more about the edge effect:
1. Use a Low Evaporation Lid
Evaporation causes a change in the concentration of salts and reagents. It affects the water and media in the circumferential wells more than those in the center of the microplate.
Evaporation means getting higher CV values. As a result, you get varying cell growth across the plate. The high concentration of media components can also alter cell physiology.
Look for how to prevent evaporation in an incubator to prevent the edge effects as much as possible. You can use a lid to reduce fluid loss.
Consider a low evaporation lid with condensation rings. It reduces the risk of both condensation and evaporation.
2. Use Other Solutions
Sealing films and tapes protect the microplates from leakage and contamination. They’re single-use, adhesive materials that you can use in a variety of applications, such as:
- Long-term storage
- Luminescence assays
- Microscopy
- Cell culture
You can also use this material to prevent evaporation during incubation and assay processing. Using a foil or clear sealing tape reduces the microplate edge effects in biochemical assays.
For cell-based assays, you can use breathable sterile tape. It allows for gas exchange while protecting the contents.
Another solution is ChipTray, which reduces evaporation. It’s also compatible with microscopy.
3. Temperature Regulation
A temperature difference is the most common cause of the edge effect. An example is using reactant liquids from the refrigerator then incubating at room temperature.
Some also incubate at 37°C to make the incubation time shorter. Higher temperatures also create a massive difference.
The peripheral wells heat up first. More reactant molecules get immobilized in these places, resulting in higher O.D. values. You get a more pronounced edge effect when you stack the plates.
Remember that the plate readers are warmer on the inside, as well. Even when you place a plate prepared at room temperature, the outside edges still warm up first.
A solution is to use a temperature regulation option. You need to maintain exact room temperature to prevent the edge effect.
Learn More About Edge Effects
The edge effects in microplate assays are a constant problem everywhere. They’re not exclusive to 96-well microplates. You can see them across all formats, like 384- and 1536-well varieties.
You have to find out the exact cause of the edge effect. After which, you can start experimenting with solutions that might work for you.
Did you find this guide helpful? To learn more, check out our other posts.