Tissue preservation is crucial for research, diagnostics, and long-term storage. The most common method is freezing, followed by storage at low temperatures.
Freezing and Cryopreservation
Freezing tissue halts cellular processes, preventing degradation. This method is particularly effective for preserving the integrity of proteins and other biomolecules essential for various analyses. The process involves rapid freezing to minimize ice crystal formation, which can damage cells. Optimal preservation requires freezing the tissue as quickly as possible after retrieval. Sometimes, the tissue may be sectioned before freezing for easier handling during later proteomic analysis. Specific protocols vary depending on the type of tissue and the intended application.
- Rapid Freezing: Achieved using techniques such as immersion in liquid nitrogen or isopentane cooled by liquid nitrogen. This minimizes ice crystal formation which could damage the tissue structure.
- Cryopreservation Media: Often specialized cryoprotective agents (CPAs) are added to the tissue before freezing to prevent ice crystal formation and protect cellular structures. These CPAs help to lower the freezing point and reduce the damage from ice crystals.
- Storage at Low Temperatures: After freezing, tissues are typically stored in ultra-low temperature freezers (-80°C) or in liquid nitrogen (-196°C) for long-term storage.
Other Preservation Methods (Brief Overview)
While freezing is the dominant method, other techniques exist, although they are less commonly used for routine preservation. These include:
- Formalin Fixation: This method uses formaldehyde to chemically crosslink proteins, preserving tissue structure but often altering the chemical composition. It's commonly used for histology.
- Embedding in paraffin wax: After fixation, tissues are often embedded in paraffin wax for easier sectioning and microscopic examination.
The choice of preservation method depends on the intended use of the tissue. For studies requiring the preservation of protein structure and function, freezing is the preferred method.
