Which microplate color to use when

Step up to the plate! But which color?…

* transparent: use for absorbance assays (e.g colorimetric assays (measuring color), or UV absorption measurement)
* black: use for fluorescence assays (GFP, fluorescent dyes, etc.)
* the black absorbs some of the light
* reduces background signal from autofluorescence (light from other molecules in there that are naturally fluorescent)
* prevents light from creeping into neighboring wells (cross-talk)
* white: use for chemiluminescence (including bioluminescence - luciferase, etc.)
* the white walls reflect light, amplifying the signal
* okay for luminescence but not fluorescence because there’s less background signal here (specific chemical reaction has to happen rather than just absorbing and transmitting light)
* gray: use when you need a compromise between high background and high signal

Some plates have transparent bottoms but opaque sides - these can be used if you need to measure absorbance and fluorescence or luminescence. And/or if you are doing cell-based assays. Having a clear bottom will let you check on the cells, ensure they’re at a good density, etc. You can also cover the bottoms of the plate if needed. These plates are also useful if you need to shine excitation light through the bottom rather than the top.

Well, what size?

Micro plates come in a variety of size formats in terms of number of wells. Probably the most common one you’ll use in the lab is 96-well (12 across and 8 down). There are also plates with fewer wells (i.e 24) which you more commonly use with things like cell culture or manually-set crystallization trays. More commonly if you’re straying from 96 when doing assays it’s to increase your well number to efficiently test lots of samples (go high-throughout, HT). You can go to 394 or 1536.

Because the plate footprint for all these is the same, the more wells you cram into, the smaller the wells are and thus the smaller your sample volume will have to be. This saves resources but requires pipetting super duper tiny volumes. This is easier for robots to work with than people…

96-well is nice because the spacing is the same as with PCR strips so you can use the same type of multichannel to work with both of them. But you need about 100-300 ul sample per well for 96, which can use up a lot of sample (and/or require you to dilute your sample lots to measure the signal).

You might be able to go up to a 384 well plate but that would be less convenient and your plate reader might not even be able to handle those plates. A compromise is half-area 96-well plates which have 96 wells but the wells are partly covered so the volume per well is smaller and you only need about 50ul per well (up to about 170ul)

There are also deep-well plates which are handy for storage but not measurements.

Other things to keep in mind…
* Bottom shape
* maximum area with square but more risk of cross-talk and not ideal for shaking
* Flat for measurements but v shaped or curved can help with sample transfer so can be used for storage or assay prep
* Coating
* Plates may need special coatings to allow cells or molecules to stick to them - or to prevent them from sticking

blog form: https://bit.ly/microplatechoosing

Here is a nice guide I found from BMG lab tech: “The microplate: utility in practice”

https://www.bmglabtech.com/en/the-mic...

more about luminescence & light-based readouts in biochemistry: https://bit.ly/luminescence_biochem &    • Light-based readouts in biochemistry:...  
    
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