Microtomes and Cryostats
Histology specimen preparation in BSL-1 or BSL-2 labs using microtomes or cryostats involves very sharp blades around your fingers. Additionally, you can be exposed to infectious materials when working with unfixed biohazardous samples, which pose a much higher risk than fixed tissue.
Read the operator manual for the microtome or cryostat and request training from your principal investigator, lab manager, or a colleague who has experience using the equipment. In addition, note whether your sample is fixed or unfixed and which biohazardous agent(s) it may harbor.
Properly Load and Unload Samples
Ensure samples are properly trimmed prior to mounting onto the stage. Cover the blade by using the provided finger guards or a protective foam guard over the blade during mounting/removal of a sample. Use forceps to remove the blade and wear two layers of nitrile gloves to help protect your skin.
Perform Routine Sanitation
Always clean the equipment between users and at the end of a session. Cryostats are more difficult to disinfect between samples since the cold can make the disinfectant build up on the knife, so it is best to finish the entire session and then perform a comprehensive decontamination by removing the stage and allowing it to come to room temperature before cleaning. Allow it to dry completely before returning it to the cryostat.
Cleaning the Microtome or Cryostat
Put on protective equipment including double nitrile gloves and a lab coat. Use a pair of forceps to carefully remove the knife. Either discard the knife directly in a sharps container or if re-using it, place in a container of disinfectant to soak. Ensure complete contact time, then use forceps and a handled brush to remove residue and scrub clean, followed by water rinse. Use forceps to remove residue, stray shavings, etc., from the interior of the mircotome and place in a biohazard bag. Soak the interior components with disinfectant, applied with a squirt bottle. Use a cloth, manipulate with forceps where possible, to scrub and decontaminate. If needed, use a handled brush to access hard to reach areas and wear facial protection because a brush is more likely to cause splatter. Soak up residual disinfectant and rinse/dry with 95% ethanol. Let air dry.
Note on Bleach
The first impulse may be to use bleach (10% bleach followed by multiple rinses of 70% ethanol), but you can protect the blade by evaluating the agents most likely to be in the samples and choosing a less corrosive alternative disinfectant.
Things to Avoid
- Do not leave the blade exposed during sample loading and unloading. This is one of the easiest ways to sustain an injury. Remember to cover the blade.
- Do not handle the blade with unprotected hands. Make sure to use forceps and wear gloves.
- Do not skip Personal Protective Equipment (PPE) - gloves can minimize or possibly prevent cuts and lacerations.
For additional guidance on microtomes, review the Biosafety Manual Section 2.1.12