What is Agarose?
Agarose is a polysaccharide derived from seaweed belonging to the genus Gelidium and Gracilaria. It is a linear polymer made up of repeating units of agarobiose—a disaccharide consisting of D-galactose and 3,6-anhydro-L-galactopyranose. In
histology, agarose is widely used due to its ability to form gels at low concentrations, which are useful for a range of applications.
Why is Agarose Used in Histology?
Agarose is primarily utilized in histology for
embedding tissue samples. The gel matrix provides a supportive medium that holds the tissue in place, making it easier to handle and cut into thin sections for microscopic examination. Additionally, agarose gels are transparent, which is essential for optical clarity during
microscopy.
How is Agarose Gel Prepared?
To prepare agarose gel, the agarose powder is dissolved in a buffer solution, typically using heat to ensure complete dissolution. The solution is then allowed to cool, during which it forms a gel. The concentration of agarose in the solution can be adjusted according to the desired gel strength and pore size, which is crucial for different histological applications.
Agarose Gel in Immunohistochemistry
In
immunohistochemistry (IHC), agarose gel can be employed to embed tissue sections for antibody staining. The gel provides a suitable environment to preserve the antigenicity of tissues while allowing the penetration of antibodies. This makes it easier to study the distribution and localization of specific proteins within the tissue samples.
Advantages of Using Agarose in Histology
Agarose has several advantages in histology: Non-toxic and Inert: Agarose is non-toxic and chemically inert, which minimizes the risk of interfering with biological processes or staining protocols.
Gel Strength: The gel strength of agarose can be adjusted by altering its concentration, providing flexibility for different histological needs.
Optical Clarity: The transparency of agarose gels ensures that they do not interfere with microscopic examination.
Ease of Handling: Agarose gels are easy to handle and manipulate, making them convenient for embedding and sectioning tissue samples.
Limitations of Agarose in Histology
Despite its advantages, agarose has some limitations: Limited Mechanical Strength: Agarose gels are relatively soft and may not provide sufficient support for very delicate or large tissue samples.
Temperature Sensitivity: Agarose gels are temperature-sensitive, meaning they can melt or lose integrity at higher temperatures, which may be a concern during certain processing steps.
Cost: High-purity agarose can be expensive, which may be a limiting factor for some laboratories.
Comparing Agarose with Other Embedding Media
Agarose is often compared with other
embedding media like paraffin wax and OCT compound. Paraffin wax is more commonly used due to its superior mechanical strength and ability to infiltrate tissues more thoroughly. However, it requires higher temperatures for embedding, which can potentially damage heat-sensitive tissues. The OCT compound is favored for
cryosectioning but lacks the transparency and inertness of agarose.
Applications Beyond Histology
While its primary use in histology is significant, agarose is also widely used in other fields such as
molecular biology for
gel electrophoresis. Its gel-forming properties are essential for separating DNA, RNA, and proteins based on size, which is crucial for numerous genetic and biochemical analyses.
Conclusion
Agarose plays a vital role in histology by providing a versatile, non-toxic, and transparent medium for embedding tissue samples. Its ease of use and adaptability for various applications make it a valuable tool in the histologist's arsenal. However, understanding its limitations and comparing it with other embedding media is essential for choosing the most appropriate method for specific histological needs.
