Electron microscopy is sensitive to tissue handling procedures. Whilst we recognise and appreciate that non-MFT service users may prefer to determine their own laboratory procedures pertaining to the fixation and handling of the tissue samples that they send to us for examination, we ask all service users to appreciate that fixation and handling procedures affording perfectly satisfactory light microscopy fixation, may not necessarily remain suitable for ultrastructural studies.
Therefore, we strongly recommend that all service users meet the following conditions for all tissue samples to be processed for EM.
Failure to do this is likely to result in sub-optimal tissue preservation and may place limitations on the ultrastructural interpretation of the sample.
Deviations from these recommendations by service users should be discussed and agreed with the Electron Microscopy Lead Biomedical Scientist before specimens are sent.
a) Samples are placed into fixative immediately upon removal from the patient. 2.5% buffered glutaraldehyde is preferred but 10% Neutral Buffered Formalin is acceptable. The transport of fresh samples from theatre or clinic for fixation within the laboratory is not advised.
b) If samples are fixed initially in Formalin, they are transferred to 2.5% buffered glutaraldehyde at the earliest opportunity and fixed at 4 – 20°C for between 24 – 72 hours, after which time the sample must be transferred to 0.1M phosphate buffer (pH 7.4) for transport (see section 4.3 for transport guidance).
c) Samples fixed in buffered glutaraldehyde are not larger than approx. 1mm3 in size.
d) Tissue must be kept hydrated in an isotonic manner before and during transport to the EM laboratory. Please note that we do not currently provide external service users with suppliers of fixative and/or buffer.
(Last reviewed 19th June 2018)