What is OCT Compound?
Optimal Cutting Temperature (OCT) compound is a water-soluble, glycol-based medium used to embed biological tissues for cryosectioning in histology. It provides support to tissue samples, allowing them to be sectioned at low temperatures without causing damage. The OCT compound is widely used in the preparation of frozen tissue sections, which are essential for various diagnostic and research applications.
Why is OCT Compound Important?
The OCT compound is crucial for maintaining the structural integrity of tissues during the freezing and sectioning processes. It prevents formation of ice crystals that can damage cellular structures, ensuring that the tissue morphology remains intact. This is particularly important for techniques such as immunohistochemistry, in situ hybridization, and fluorescence microscopy, where preserving fine details is essential for accurate analysis.
1. Tissue Preparation: The tissue sample is first dissected and prepared for embedding. It should be free of excess moisture to ensure optimal results.
2. Embedding: The tissue is placed in a mold, and OCT compound is poured over it to completely cover the sample. The mold is then placed on a freezing platform, typically cooled with dry ice or liquid nitrogen, to rapidly freeze the tissue and the OCT compound.
3. Sectioning: Once frozen, the embedded tissue is mounted onto a cryostat. Thin sections, usually 5-20 micrometers thick, are cut using a microtome attached to the cryostat. These sections can then be mounted onto slides for further staining and analysis.
Advantages of Using OCT Compound
1. Preservation of Tissue Morphology: The OCT compound prevents the formation of ice crystals, preserving the fine details of the tissue's structure.2. Ease of Use: The compound is easy to handle and does not require complex preparation steps, making it accessible for routine laboratory use.
3. Compatibility: The OCT compound is compatible with a wide range of staining techniques and does not interfere with most reagents or detection methods.
Limitations of OCT Compound
Despite its advantages, the OCT compound has some limitations:1. Artifact Formation: Improper freezing or embedding can lead to artifact formation, which may complicate the interpretation of results.
2. Limited Long-Term Storage: Tissues embedded in OCT compound are generally not suitable for long-term storage, as they may degrade over time. They are best used shortly after preparation.
3. Specialized Equipment: The use of OCT compound requires access to a cryostat and other specialized equipment, which may not be available in all laboratories.
Frequently Asked Questions
Can OCT compound be used for formalin-fixed tissues?
OCT compound is typically used for fresh or flash-frozen tissues. While it is possible to embed formalin-fixed tissues in OCT compound, this is less common and may require additional steps to ensure proper sectioning and analysis.
How should OCT-embedded tissues be stored?
OCT-embedded tissues should be stored at -80°C to prevent degradation. It is important to minimize freeze-thaw cycles, as these can damage the tissue and compromise the quality of the sections.
Can I use OCT compound for electron microscopy?
OCT compound is not suitable for electron microscopy as it does not provide the necessary support for ultra-thin sectioning and can interfere with electron beam penetration. Alternative embedding media, such as epoxy resins, are used for electron microscopy.
How do I remove OCT compound from tissue sections?
OCT compound can be removed from tissue sections by washing with phosphate-buffered saline (PBS) or other suitable buffers before staining. This ensures that the compound does not interfere with subsequent staining procedures.
