What is Formalin Fixation?
Formalin fixation refers to the process of preserving biological tissues by immersing them in formalin, a solution of formaldehyde in water. This technique is essential in
histology for maintaining the structural integrity of tissues and preventing autolysis and putrefaction.
Why is Formalin Used?
Formalin is preferred because it effectively cross-links proteins, stabilizing the tissue architecture. This cross-linking forms covalent bonds between amino acids, preserving the morphology and enabling the tissues to withstand subsequent
histological processing and staining procedures.
How Does Formalin Fixation Work?
Formalin penetrates tissues and reacts with amino groups in proteins to form methylene bridges. This process helps in maintaining the structural detail of the tissue and prevents enzymatic degradation. The fixation process typically takes anywhere from a few hours to a couple of days, depending on the size and type of tissue.
Tissue Collection: Tissues are collected and immediately immersed in formalin to prevent degradation.
Fixation: The tissue is left in formalin for a specific period, allowing the fixative to penetrate and stabilize the tissue.
Washing: After fixation, tissues are washed to remove excess formalin, which can interfere with subsequent steps.
Concentration: Use buffered formalin at a concentration of 10% formaldehyde.
Duration: Adjust fixation time based on tissue size and type, avoiding prolonged exposure.
Temperature: Perform fixation at room temperature to ensure uniform penetration.
Alternatives to Formalin Fixation
While formalin is widely used, other fixatives like
glutaraldehyde,
ethanol, and
Bouin's solution may be used depending on specific requirements, such as electron microscopy or antigen preservation.
