Freeze drying is a common preparation technique for biological samples such as leaves, but
Plymouth Electron Microscopy Centre (PEMC) also have聽 Cryo-Scanning Electron Microscopy (cryo-SEM) capabilities which are available on our JEOL 6610 LV SEM.听
Cryo-SEM allows the samples to be imaged in their hydrated state, preserving structures that would be lost during freeze drying. The samples are plunged into a liquid nitrogen slush and transferred into the specimen chamber, before sublimating them to remove any surface ice and sputter coating. The sample can also be fractured to reveal the internal structure at this stage, and imaging is carried out on a cold stage to prevent thawing.
If you think that cryo-SEM would be beneficial to your experiment, please contact
Mr Glenn Harper to discuss it further.
Freeze dried banana skin
To visualise the differences between freeze drying and cryo-SEM, we decided to image some banana skin. A small piece was cut and freeze dried overnight for analysis. This process removes the water from within the sample through sublimation, and is a useful sample preparation technique for biological samples that do not require sectioning for
Transmission Electron Microscopy (TEM) or Scanning Electron Microscopy (SEM).听
The freeze dried banana skin retained a lot of structure, albeit dehydrated, and can provide valuable information about the structure of the plant. However, we found the difference between this sample and the hydrated sample imaged through cryo-SEM quite stark.
Cryo-SEM banana skin
The sample of banana skin that was analysed using our cryo-SEM system was taken from directly next to the freeze dried sample on the same banana, making this a directly comparable test. As seen in these images, the hydrated sample is remarkably different. Significantly more detail and fine tissue is preserved, and reveals that the holes in the freeze dried sample developed during the drying process.
Whilst cryo-SEM has many uses, it may not be the best technique for your particular experiment. It can be a lengthy process and only one sample can be analysed at a time, so it is best to discuss the goals of your study with the team at PEMC to ensure the most efficient use of time and instrumentation.听
Cherry blossom petal
Coronation chicken sandwich filling