Tissue Preparation for Frozen Sections

Materials needed:
Cold PBS OCT (Frozen tissue matrix)
Peel-away tissue mold Fixative (2% PFA, 4% PFA, 10% buffered formalin)
Liquid nitrogen and Dry ice  


1. Have the liquid nitrogen or dry ice ready before dissecting tissues
2. Label tissue mold and fill the bottom of the mold with a thin layer of OCT (avoid air bubble). Mold size
      should be > 4x tissue 3D size
3. Place fresh tissue in cold PBS and wash out the blood --> absorb the PBS from the tissue with gauze or
      kimwipes (for fixed tissue: wash 3 x 3min in cold PBS)
4. Place tissue in pre-labeled molds filled with OCT. The cutting side need to be facing down to the
      bottom of the mold.
5. Fill the entire mold with OCT to cover the entire tissue (avoid air bubble)
6. Snap freeze the tissue block in liquid nitrogen for 30 seconds --> place tissue block on dry ice (if block
      is left in liquid N2 too long, it may crack)
7. If liquid N2 is unavailable, freeze tissue block in dry ice (tissue covered with dry ice) for 30 min
8. On dry ice, place frozen tissue blocks inside plastic bags and tighten the bags to prevent the OCT from
      drying out (dried block will crack)
9. Transfer the frozen tissue to Photopath for cutting service, or store frozen tissue in -80°C freezer and
      transfer later (always carry the frozen tissue on dry ice)



Core Procedures

Tissue Preparation for Frozen Blocks
Tissue fixation with Formalin (for paraffin blocks)