Paraffin services

Decalcification

This is a technique that removes minerals from bone and other calcified tissues to improve the quality of the sections. Decalcification is carried out after the specimen has been thoroughly fixed and prior to tissue processing to paraffin.

Tissue processing

After fixation, samples are brought to the Core where they are placed in tissue cassettes and run in an automated tissue processor. This is a 3 step process that removes water from the tissue and replaces it with a medium (i.e. paraffin wax) that solidifies to allow thin sections to be cut. The first step is dehydration through a series of alcohols (70%, 80%, 90%, and 100%) to remove water from the tissue. This is followed by a clearing step using a solvent (i.e. Xylene) that removes the dehydrating agent from the tissue, since ethanol and wax are immiscible. Lastly, Xylene is removed from the tissue and infiltrated with molten paraffin wax. The tissue is now ready to be embedded in wax.

Agar pre-embedding

Agar can be used to embed samples prior to paraffin embedding. This is useful for cell pellets, very small samples, or if more than 1 sample needs to be embedded together in a specific orientation.

After processing, samples are placed in a specific orientation in a mold containing melted paraffin, which hardens and forms a block upon cooling. The block provides support to the tissue when they are cut.

Paraffin sectioning is the technique of cutting thin slices of tissue that has been fixed and embedded in wax using specialized equipment called a microtome. Sections are then flattened in a heated water bath, floated onto slides and dried.