Question: What sample handling methods can be implemented to minimize the likelihood of FFPE tissue detachment for Visium CytAssist Spatial Gene Expression?
Answer: FFPE tissue sections can detach during on-slide workflows. Tissue adhesion to slides is impacted by tissue morphology, tissue processing (fixation and embedding), and other factors such as sample handling. Below are some best practices related to sample handling that should minimize the risk of detachment:
- Allow the tissue block sufficient time in the ice bath to ensure proper hydration. Optimally hydrated blocks should appear smooth and shiny. Dehydrated blocks are prone to cracking. Sections that are cracked can impact adhesion.
- Ensure the microtome is set up properly such that there are no loose screws. Unstable microtome components can cause vibration leading to tissue section damage and/or uneven section thickness. Uneven sections can be more likely to detach from slides.
- Clean the workstation (microtome and water bath) before use. Static electricity can accumulate on the blade holder after facing blocks and contribute to tissue curling. Particulate can gather in the water bath and impact tissue smoothness during floating, if on the surface.
- Make sure to use a new and clean microtome blade for sectioning. Blades used for facing can accumulate static electricity and blades that are dull, damaged, or that have oils on them can impact tissue attachment to slides.
- Utilize recommended positively charged plain glass slides for tissue placement (see this article for details).
- Utilize thinner tissue sections. The assay supports 3-10 µm but thinner sections (3-5 µm) are less prone to detachment than thicker sections.
- The water bath should be filled with Ultrapure/MilliQ water and free of bubbles or particulate. A laboratory wipe should be glided over the surface of the water to ensure that the surface is uniform and free of any debris. Bubbles or particulate under the tissue section can lead to poor tissue adhesion.
- After transfer to the water bath, allow the section to float until it is free of folds and wrinkles. Perform a quality check by collecting the section on a plain glass slide and inspecting for tissue damage under a microscope. Sections with damage can negatively impact adhesion. Below are section phenotypes that should be avoided:
- Bubbles under the tissue
- Properly dry sections in accordance with our documentation. Failure to effectively dry sections can increase the risk of detachment.
- During Deparaffinization, allow the slide to equilibrate to room temperature after the 60°C (2 h) incubation before immersing in solution. Quick changes in temperature can impact adhesion.
- Gently add and remove reagents from slides. Forceful removal or addition of reagents can agitate tissue and lead to detachment.
For product-specific guidance to minimize detachment and illustrations of sample handling artifacts, please see the following documentation:
- Visium CytAssist Spatial Gene Expression FFPE Tissue Preparation Guide
- Staining Demonstrated Protocols (H&E or Immunofluorescence)
Products: Visium CytAssist for FFPE