To run just about any experiment on the microscope, you have to put cells in a dish, on a slide or in a microplate. Most of our experiments are run in a microplate, so I will concentrate on these style plates. Microtiter plate it turns out is a registered trademark of Cook Engineering Company, so I will use the generic term microplate (1).
Depending on the experiment, there is a wide variety of microplates. The more common plates are 6, 12, 24, 48, 96 and 384 well plates. There are plates with yet higher numbers of wells: 1536, 3456 and 9600, these plates are very difficult to manually pipette into, designed for automation. There are different styles of plates as well, round and square as well as different volumes and different coatings. As with anything, it’s important to pick the best plate for the experiment and to be aware of some issues involved with plates. Since we do visible imaging and try to have multiple variations in each experiment, we shoot for smaller volume higher density plates.
For example, if the experiment involves the effect of extract concentration on yeast cell growth, you will need a number of wells to look at the effect. Let’s say you want to look at 5 different concentrations of extract, then a negative control and a positive control, that’s 7 wells for one concentration of yeast. Next I may want to see if there is an affect with yeast concentration as well, so maybe 3 different concentrations. Now we are up to 7 x 3 = 21 wells. If we also want to look at 4 different strains of yeast, that’s 21 x 4 = 84 wells. You can see that very quickly, based on the experiment along with the controls, there are quickly a lot of wells to prepare for an experiment.
Here are a few things to consider with the plates, for an experiment:
Since you will be imaging through the plate, be careful not to touch the bottom of the plate. If you for example wipe the bottom with a paper towel, the plate will be scratch and you won’t get very good images.
If you are doing fluorescent imaging, we suggest using black plates with clear bottoms, so no stray light gets into the adjacent samples.
Not all plates are created equal. Make sure the bottoms are clear and flat. It’s best to try a small sample before purchasing a lot of these plates, there is a lot of variation in the industry. Many plates aren’t necessarily designed for bottom imaging.
Some plates have shallow wells, so if you plan to image at high magnification, it may be difficult to get the objective close to the bottom of the well. Look for plates where the wells are close to the bottom of the plate.
If you are planning to use phase imaging, select larger well plates. A phase image will only work in the center of a 96 well plate, where the meniscus doesn’t distort the light. There is more area to image with say a 48 well plate and no real phase in a 384 well plate.
The quality of the images, both visible and fluorescent in many cases depend on the quality of the microplate. It is always best to concentrate on getting the best images for image analysis, so take some time and pick the best microplate for the application.