What is Over Fixation?
In histology,
fixation is a critical step in tissue preparation that preserves the structural integrity and biochemical composition of samples. Over fixation occurs when tissue samples are exposed to fixatives for a prolonged period, leading to excessive cross-linking of proteins and other biomolecules. This can hinder subsequent histological and molecular analyses.
Causes of Over Fixation
Several factors can contribute to over fixation:Effects of Over Fixation
Over fixation can have several adverse effects on tissue samples: Excessive cross-linking can mask antigenic sites, affecting
immunohistochemistry results.
It can lead to increased tissue hardness, making
microtomy more difficult.
Over fixed tissues may exhibit poor staining quality, impacting histological analysis.
RNA and DNA integrity may be compromised, affecting
molecular biology studies.
How to Avoid Over Fixation
To prevent over fixation: Follow standardized protocols for fixation times and concentrations.
Use appropriate fixatives for specific tissues and analyses.
Control the temperature during fixation.
Regularly monitor and document fixation conditions.
Reversing Over Fixation
While it is challenging to fully reverse over fixation, some steps can mitigate its effects: Using antigen retrieval techniques can help unmask antigenic sites for
immunostaining.
Modifying staining protocols to enhance contrast.
Employing enzymatic digestion to soften tissues for better sectioning.
Conclusion
Over fixation is a common issue in histology that can significantly impact the quality of tissue analysis. Understanding its causes and effects, and implementing strategies to minimize it, are essential for accurate and reliable histological and molecular studies.
