Usually, the lids that come with most plates are sufficient for the needs of most assays. Some assays don’t need lids, or use the plate above it in stack as a lid (e.g. in the BioStack). However, items to be stored long-term (e.g. compound stock plates) or protected from evaporation (e.g. assays that are heated) should be sealed.

There are 4 main options for sealing plates in the CSC:

1. For most cases, you can buy your own manual sticky seals. See below for more details on what to order.
2. For STACKS of many plates, it can be faster to use the new HJ Bioanalytik SealPeel automated sealer, operated by the Explorer PC (either within PlateWorks robotic scheduler or HJ software). Note that not all plates are compatible (e.g. PhenoPlates are not). It does not use any heat, the glue is in microspheres that make it DMSO-compatible, and it is clear (therefore can be used with brightfield on the Phenix or top read on the EnVision).
3. For MASS SPEC plates to be used with the automated injector, use the old Agilent PlateLoc heat sealer. It does not use any glue (therefore solvent-comaptible), is piercable, and blocks light (foil). The CSC DOES NOT schedule use of this instrument on our calendar, bill for its use, or pay for replacement seal rolls. We do offer training, we maintain it, and we have rubber sealing rollers and brayers to use while the plate is still hot. Note that this device is old and finicky. Usually, if having problems, the seal roll needs to be re-fed, and the instructions for this are on a card located near the sealer (and on this YouTube video). Below are photos of our old PlateLoc’s screen, to help decode its messages.

   

4. Other unusual cases: We sometimes see reusable cap mats for 96-well plates, especially for the deep well plates of natural product extracts. There are also cap strips, usually for 8 wells in a column, either on a 96-well plate or a strip tube.

   

Sticky seals commonly used by the CSC users:

• For DMSO-dissolved chemicals, PolarSeal Aluminium Microplate Seals, Thomas Scientific 1152A34 for ~$1.50 each.
• For overnight incubation of microbial cultures with minimal evaporation at 37 degrees, either Breathe Easy Sealing Membrane, Millipore Sigma Z380059 for ~$1 each (is opaque, so fine for bottom-read fluorescence on the plate reader or microscope) or the even thinner Breathe Easier Sealing Membrane, Millipore Sigma Z763624. Note that these become sticky over time when moist and warm, so your stacks of plates will stick together and can jam the stacker. The sticky membrane can also stick inside of devices such as the EnVision, depending on the plate geometry (will need the middle to be recessed).

Feel free to submit your favorite seal brand/products for your current applications, so we can recommend them to others.

Sticky seal product selection criteria:

• WHY are you sealing? For sterility? Compound stability? Minimize solvent evaporation? To prevent spill when dropped or well cross-contamination?
• Will you be needing to peel the seal off again? With the automated peeler (which is very picky about seals)?
• Are there LIVE CELLS or other instances requiring gas exchange?
  • There are semi-permeable seals that allow CO2 and O2 to exchange but not H2O (so your plates don’t dry if left for a long time, especially if heated). We recommend “Breathe Easy” brand name.
  • These products can be sterile or not, and can be opaque or not. Need to be clear if using with brightfield on Phenix or top read on EnVision – otherwise the opaque ones work better.
• Does it need to be solvent-resistant? What solvent? Under regular or extreme conditions?
  • For example, for compound libraries.
  • The problem is that glue dissolves in DMSO, making a sticky, contaminating mess. It is a real problem not to be disregarded! Let me save you the trouble!
  • There are DMSO-resistant glues and more expensive microsphere solutions.
• Do you care about light-blocking?
  • Seals are typically either a metal foil (blocks light) or a clear plastic.
  • Some compounds are light-sensitive.
  • Clear plastic will allow absorbance and top-read on the EnVision as well as brightfield on the Phenix. If you need UV light, then will need to be special UV-clear plastic.
• Do you care about sterility?
• Do you care how much they cost, or care more about how well they work? There are very cheap PCR plate seals but they don’t stick well (we use them when storing large collections of screen assay plates that are no longer in use, but being stored for a few months just in case we find a need).

How to work with a seal:

• When removing a seal, always start by securing the plate with one hand firmly to the bench. Then take your other hand and peel from a corner, in a diagonal direction.
• This is very important, to prevent the plate from moving around and spilling.