How Are Tissue Samples Preserved?
Tissue samples are preserved using various methods, depending on the intended use and the type of tissue. The goal is to maintain the tissue's structure and composition, preventing degradation and ensuring its suitability for analysis.
-
Formalin Fixed Paraffin Embedded (FFPE) Tissue: This is a standard method where the tissue is first treated with formalin, a fixative that preserves the tissue's structure. The tissue is then embedded in paraffin wax for easier sectioning and analysis. [Source: Komen.org]
-
Freezing: Tissues can be preserved by freezing them at ultra-low temperatures, such as in liquid nitrogen vapor phase (-150°C) to inactivate enzymes. This is ideal for preserving biological markers and chemicals sensitive to higher temperatures. [Source: Tissue Bank Information]
-
Freezing at -20°C or -80°C: While less effective than liquid nitrogen vapor phase storage, freezing at -20°C or -80°C is commonly used for shorter-term storage. [Source: Stirling Ultracold, NCBI]
-
Ethanol: ≥95% ethanol is another effective preservation method, particularly useful for preserving some types of tissue. [Source: MVZ Handbook]
-
RNA Later: This reagent stabilizes RNA in tissue samples, making it suitable for RNA-based analyses. [Source: MVZ Handbook]
Considerations for Preservation:
-
Storage Time: Short-term storage may use refrigeration or freezing at -80°C, while long-term storage generally requires ultra-low temperature freezing in liquid nitrogen vapor. [Source: Stirling Ultracold]
-
Intended Analyses: The choice of preservation method depends on the type of analysis to be performed. DNA analysis may require different methods than those used for histological examination. [Source: Frontiers in Zoology, NCBI]
-
Vacuum Preservation: Some innovative methods involve maintaining tissues under vacuum, often at 4°C, to preserve certain types of cells for isolation. [Source: NCBI PMC]
Examples of long-term storage practices include maintaining specimens in an underground warehouse at -16°C. [Source: NCBI Bookshelf] Decades-old samples, preserved using appropriate methods, can even be reanalyzed with newer technologies. [Source: University of Alaska Museum]
Conclusion
The preservation of tissue samples is critical for research and diagnostics. The optimal method depends on several factors, including the tissue type, intended analysis, and desired storage duration.
