The formalin-fixed paraffin-embedding (FFPE) technique is essential for preserving tissue specimens for long-term storage. This method maintains the integrity of proteins and cellular components while ensuring tissue morphology is not compromised.
Formalin-fixed paraffin-embedding or FFPE technique allows the preservation of fixed, dehydrated, and cleared tissue specimens within paraffin blocks for long-term storage. FFPE preserves proteins and other vital intracellular components without compromising the tissue morphology.
Deparaffinization, or the removal of paraffin wax surrounding the embedded tissue, is a critical step before processing any FFPE tissue specimen for downstream analysis. To begin deparaffinization, start with a glass slide carrying an unstained FFPE tissue section of interest having an appropriate thickness.
Immerse the tissue section in a xylene bath and incubate for the desired duration. Xylene, an organic solvent, dissolves the paraffin wax that has embedded and penetrated the tissue. The complete removal of paraffin wax exposes the fixed and dehydrated transparent tissue specimen.
Following deparaffinization, treat the specimen with absolute ethanol. Ethanol displaces and removes any traces of xylene from the tissue section. Subsequently, immerse the tissue in decreasing concentrations of ethanol. The process rehydrates the tissue for downstream histological analysis.
Finally, leave the slide undisturbed for the desired duration. This step allows ethanol and water to evaporate and obtain a dry rehydrated tissue section.
To begin, prepare 10 micrometers of unstained formalin-fixed paraffin-embedded sections. Place the slides in a glass slide holder and fill it with xylene, making sure that all tissue on the slide is submerged. Leave the slides in xylene for 15 minutes. Then, pour out the xylene while holding the slides with a pipette tip so that they do not fall out. Pour in more xylene to the same level as before and repeat the incubation.
Pour out the xylene and fill the slide holder with 100% ethanol, making sure that all the tissue on the slide is fully submerged. Leave the slides in the ethanol for 3 minutes. Then, replace the ethanol with fresh ethanol and allow them to incubate for two more minutes. Pour off the ethanol and remove the slides. Carefully place them face up on a clean paper towel and allow them to dry for 10 minutes.
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