Tissue processing

From the fresh sample to the finished paraffin section, several steps are required.

Fixation

In the fields of histology, pathology and cell biology, fixation is the preservation of biological tissues from declaydue to autolysis or putrefaction.

We fix in 4% PFA in PBS pH7.4 for 24 to 48 hours

Dehydration

The tissue is successively saturated with alcohol in increasing concentrations (ascending alcohol series).

50%-60%-70%-70%-96%-96%-100%-100%-100%

Intermedium

After dehydration, the tissue must be soaked with a reagent that mixes equally with both alcohol and paraffin. Xylene is usually used for this purpose.

Embedding

Radiographic specimens are necessary for microscopic examination. The hardening of the tissue through fixation is not sufficient to produce sufficiently thin sections. It is necessary to embed it in substances that can be cut: usually paraffin.

Sectioning

The (paraffin) sections, which are usually less than 10 µm thick, are produced using a microtome. The sections are mounted on glass slides.

Staining

In order to achieve the necessary contrast for an assessment in the microscope, the sections are treated with various dyes.

Microscopy

Depending on the size of the specimen, lenses with between 4x and 100x magnification are available.