Fixing, Processing, Sectioning, Staining

Histology is the study of microscopic tissues and their structures. It is an important part of biology, medicine and other sciences. Histology sample preparation for observation under a microscope is a delicate process using specialized techniques that are essential for returning accurate and quality results. Preparation includes fixing, processing, sectioning, and staining.

1. Fixing

The first step in preparing histology samples is fixing, or tissue fixation.  In this step tissue samples are “fixed” in a way that preserves the most natural possible state as to prevent decay. Many types of fixative exist, though many laboratories personnel use 10% neutral buffered formalin. It takes between 24-48 hours for a tissue sample to be fixed if a proper formalin-to-specimen ratio of 10:1 is used. For optimum results, the sample should be fixed as soon after collection as possible.

2. Processing

During processing, the tissue is dehydrated using alcohol to remove any water or fixation from the sample. The histology samples are then cleared to remove the alcohol and allow a paraffin wax to penetrate the sample. Lastly, the specimen is embedded in a large block of paraffin wax. When the block hardens it creates support for the sample during the next step of sectioning.

During processing, alcohol is used to dehydrate the tissue and remove any water or fixation from the sample.

During processing, we dehydrate the tissue using alcohol to remove any water or fixation from the sample.

3. Sectioning

Sectioning is when the sample is cut into pieces to be placed on a slide. The wax block is chilled for 10 minutes beforehand. Using a microtome, thin slices are cut from the block, usually about 5 µm thick. Once the slices are cut, they are transferred to a warm water bath until they are placed on a charged slide. Slides are then dried, allowing the excess paraffin wax to melt away from the sample.

4. Staining

The final step in preparing a histology sample is staining. Stains provide contrast to sections of tissue which makes viewing structures of the sample easier. After staining a slide, a cover slip is added over the specimen to protect it.

Histology Sample Test Requests

• Food Laboratory needed for meat speciation detection by histology of non-strained beef tissues in beef burgers. E.g. Heart, lung etc.
• Histology Laboratory needed for histological (H& E) studies on following area 1. Cerebrum Male rat control × 200 & × 400 2. Iscahemia for Carotid Vessel for 25 minutes × 200 & × 400 then perfusion for one hour 3.Ischaemia for 3-5 minutes then perfusion for one hour ×200 ×400
• University researcher needs clinical pathology laboratory for cytology and histology of various cancer samples including cervical cancer, breast cancer, pancreatic cancer, bladder cancer, and bile duct cancer.
• Veterinary Medicine Laboratory needed for post-treatment equine tendon histology and ELISA for growth factors with commercially available tests.
• CAP or CLIA certified histology laboratory needed to process and analyze paraffin blocks of human skin samples that we would like to have cut for slides, and then subsequently analyzed for H&E and Gomori?s Trichrome.
• Europe University Researcher needs histology laboratory for Immunohistochemistry for CD52 on a tissue slide (paraffin-embedded, formalin fixation.
• LONG-TERM: Preclinical CRO Immunology/Histology Laboratory needed for non-GLP histological processing from buffered formalin fixed tissues (human and animal, size 6 mm diameter, approx. 40 um thick) into H&E-stained slides (at 3 different levels) and about 10 FFPE unstained slides for further subsequent immunohistochemistry,
• France University researcher needs histology laboratory for Immunohistochemistry on 1 slide (TMA) for research antibodies (already purchased or not, examples ALDH, SOX).
• France university needs Histology Laboratory needed for Immunohistochemistry for anti-mitochondria antibody: send slide with tissue section (formalin fixed, paraffin embedded specimen).

See more Histology Projects.

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