Paraffin Sections of Conventional Tissues

Paraffin sectioning is the procedure of cutting thin slices of tissue that has been dehydrated and infiltrated with wax using specialized equipment. This tissue is then embedded in wax before being cut on a microtome. Paraffin sections are more physically stable and superior to frozen sections in maintaining tissue morphology with less damage. But due to the wax infiltration process, paraffin sections are not optimal for some staining processes.

• Fix dissected tissues with 10% formalin for no less than 48 hours at room temperature. Inadequately fixation can make tissues dehydrated during tissue processing and become hard and brittle.
• Rinse the tissue with running tap water for 30-40 min to eliminate the formaldehyde.
• Dehydrate the tissues in EtOH baths in the following order, 70% Ethanol 20 min (x1), 95% Ethanol 20 min (x2), 100% Ethanol 20 min (x2).
• Clear the tissue in xylene for 2 times, 20 min each.

• Melt the paraffin prior to adding the tissue. Incubate the tissue in a 65°C paraffin bath for 2 times, 30 min each.
• Pour melted paraffin into paraffin block mold. Place the tissue well in the mold and wait for its cooling down (15-20 min).
• Section the paraffin-embedded tissue block in 4-10 μm thickness slides on a microtome and float in a 37°C water bath containing deionized water.
• Float the sections onto clean glass slides and microwave at 65°C for 15 min, then the tissue binds to the glass. Slides can be stored overnight at room temperature or be used in immunohistochemical staining immediately.

• Paraffin section slides can be stored at room temperature for a long time.
• Routine tissue is cut at 3-5 µ, typically one cell thick, one section per slide, one slide per block. Biopsy tissue is usually cut 2-3 µ, a few sections per slide, 2-3 slides per block.
• Epitopes of target antigens are likely to be damaged by high temperature or fixative in the whole process and a antigen retrieval procedure is needed.

Whole Slide Imaging

Transmission Electron Microscopy (TEM) Service

Immunohistochemistry (IHC), Immunofluorescence (IF) Service