Preserving biological specimens involves stabilizing their structure and preventing decomposition. This is primarily achieved through fixation and storage.
Fixation Methods
Fixation is the critical first step, halting cellular processes and preventing decay. A common and effective fixative is formaldehyde, often used as a 40% solution called formalin. Formalin's action cross-links proteins, preventing enzymatic degradation.
- Formalin (40% formaldehyde solution): This is a widely used fixative for a broad range of specimens, from small tissue samples to entire organisms. It effectively preserves the morphology of the specimen. However, it is a known carcinogen and requires careful handling and disposal.
Storage Methods
After fixation, specimens need appropriate storage to maintain their preservation:
- Storage in Formalin: Following fixation, specimens can be stored long-term in formalin. Regular changes of the formalin solution may be necessary to maintain effectiveness.
- Transfer to Ethanol or Isopropyl Alcohol: After formalin fixation, some specimens are transferred to ethanol or isopropyl alcohol for long-term storage. This minimizes the risk associated with formalin.
- Embedding in Paraffin: For microscopic examination, tissues are often embedded in paraffin wax after fixation and dehydration. This allows for thin sectioning and staining.
- Cryopreservation: For some applications, freezing specimens in liquid nitrogen or at ultra-low temperatures preserves them for long periods.
Other Considerations
The specific preservation method will depend on the type of specimen, intended use (e.g., research, museum display), and available resources.
