SEM and TEM sample preparation (bio) service

Our sample preparation service offers all or some stages of preparing the sample to be imaged on SEM or TEM depending on your needs and on the sample.

For TEM, the sample is fixed, post-fixed, dehydrated and embedded in resin. The sample is then microsectioned and mounted onto a grid for TEM imaging.

For SEM, the sample is fixed, post-fixed in some cases, dehydrated and mounted onto a stub. Finally, the sample is coated with carbon or gold to make it conductive for imaging.
 

The process for TEM sample preparation

Once we agreed on number of samples, we proceed to prepare 1 or all the samples, depending on the nature of the samples and if we expect difficulties. The sample(s) are fixed, post-fixed, dehydrated and embedded in resin. The embedding may take several forms – if we are embedding a tissue slice, we would embed it flat between 2 sheets of plastic. If we are embedding pieces of tissue or cells, we use capsules or moulds.
Lastly, we microsection the embedded sample (generally between 50 and 80 nm thick sections), mount the sections on a grid, post-stain it and image it. We then contact you and either send you the grids for TEM imaging at your facility or we image it here and send you the pictures. If you are happy with the quality of the sample preparation, we proceed with the rest of the samples, whether we are to process them or microsection them.
 

The process for SEM sample preparation

The sample preparation for SEM is very much dependent on the nature of the biological sample and on its size. The sample may be generally dry, such as insect samples or it may need to be fixed and dehydrated, such as plant samples. If you have a protocol that you would prefer us to use, we are happy to follow your instructions.
Once the biological sample is dehydrated, it is coated with carbon and/or gold to obtain conductivity for SEM imaging. We may process one sample as a pilot for you to assess its quality and whether any part of the sample preparation may need to be adjusted. Once you are happy with the pilot sample, we proceed preparing the rest of the samples.
 

FAQs

How much does a sample preparation cost?

The cost very much depends on the technique selected, as TEM is more time consuming, it is more expensive. The next thing that will affect the cost is the type of the sample and how much work is needed to prepare it for processing. For example, if you send us whole fixed organ, such as a kidney, we may need to slice it with vibratome first to be able to prepare the organ’s region you are interested in. On the other hand, a sample that does not need any pre-processing, we may be able to proceed preparing for TEM straight away, such as using cell cultures, whether adhered on a support or spun in a pellet.
 

How long does it take for the sample to be prepared?

This depends on the technique – SEM is much faster and takes 1 or 2 days. Sample preparation for TEM, on the other hand, takes around 10 days from start to finish.
 

How many samples can you process?

For TEM it is easy to batch the samples, where we can prepare around 10-20 samples at one time. Preparation for SEM depends on the size of the samples, but since it is a faster technique, we usually prepare samples one after another.
 

I heard that samples may shrink during preparation and create artefacts.

Yes, that is correct, this may happen during chemical fixation and alcohol dehydration. Regarding TEM, we can treat the samples so the dehydration process does not lead to shrinkage. For this purpose we freeze the sample instantly and substitute the frozen medium with alcohols at very low temperatures (around -90 degrees C). This procedure reduces shrinkage of extracellular matrix and extracellular spaces between cells in tissues.

Regarding SEM we may discuss various protocols with you and their advantages and disadvantages so you can make the best choice for your samples.
 

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