Sealing PCR Plates

Polymerase chain reaction (PCR) has become an important tool in many fields, including molecular diagnostics. Increasingly, laboratories use 96- and 384-well plates instead of individual tubes since they simplify and accelerate the handling of many samples at once, allowing for higher throughput. PCR plate seals are used to protect the samples used against contamination and evaporation.

There are three main platforms to seal PCR and rt-PCR plates, including heat sealing, adhesive seals, and cap strips. Regarding plate choice, it is important to always use a PCR plate, and not tissue culture plates, flat bottomed, or round plates. White PCR plates are often the go-to choice because of their inherently low autofluorescence which can improve quantification. Plates of a different color may increase the variation of fluorescence between wells and significantly influence the PCR results. For this reason among others, calibration plates are frequently employed as an additional failsafe to ensure reproducibility.

If special chemicals are used such as acids, bases, or organic solvents, the compatibility of the seal with the substance must be assessed. Below are a few considerations on choosing the correct seal for your PCR application.

Considerations For Sealing PCR Plates
Will the plate need to be shipped and/or stored on ice?	Check the manufacturer's website to see if the seal will adhere unintentionally to dry ice.
Is the seal heat activated or adhesive?	Ensure that the right equipment is available for heat activated seals before purchasing. If heat activated, consult the manufacturer's website for appropriate heating instructions.
Will the seal be easily punctured or torn?	This may be an issue with foil seals. If foil seals are used, it is recommended to apply a plastic seal on top of the foil.
Will strip caps be used?	Removing strip caps may lead to cross contamination between wells.
Have you tested the plate seal prior to PCR?	A good seal will allow vortexing at high speeds with no visible liquid marks around the wells. After sealing, clear marks should be visible where the adhesive has stuck to the plate. After testing the seal, ensure there are no visible gaps in the seal around each well.

Below are instructions for correctly applying an adhesive seal to a PCR plate.

1. Align the adhesive seal on the PCR plate so that all the wells are covered.
2. Seal the plate using a plate applicator or other flat device by moving the flat edge of the applicator back and forth across all wells on the plates, both horizontally and vertically.
3. Ensure the seal is secured firmly around all edges and wells of the PCR plate.
4. If applying the foil seal ensure there are no wrinkles in the foil to avoid potential leakage.
5. If using a foil seal, apply a plastic seal on top for shipping and/or storage.

Products

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References

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Investigation of the chemical resistance of sealing systems for PCR Plates, Deepwell Plates and Microplates
Effects of Plate Position, Plate Type and Sealing Systems on Real-Time PCR Results
Plate Sealing Guide