Phosphate Buffered Saline (PBS) - Histology

What is Phosphate Buffered Saline (PBS)?

Phosphate Buffered Saline (PBS) is a buffer solution that is commonly used in biological research. It is composed of sodium chloride, sodium phosphate, and, in some formulations, potassium chloride and potassium phosphate. The solution mimics the ionic concentration and osmolarity of the human body, making it an ideal isotonic buffer for various laboratory applications.

Why is PBS Used in Histology?

In histology, PBS serves multiple purposes due to its non-toxic and isotonic properties. It is used for washing tissue sections, diluting reagents, and maintaining cell integrity during various histological procedures. The buffering capacity of PBS helps maintain a stable pH environment, which is crucial for preserving the physiological conditions of tissues and cells.

How is PBS Prepared?

PBS can be prepared in the laboratory by dissolving the appropriate amounts of sodium chloride, sodium phosphate, and, if needed, potassium chloride and potassium phosphate in distilled water. The pH is usually adjusted to 7.4 using hydrochloric acid or sodium hydroxide. Ready-to-use PBS tablets or powder are also commercially available, which can be dissolved in distilled water to make the solution.

Applications of PBS in Histology

Some common applications of PBS in histology include:

Washing tissue sections: PBS is used to rinse tissue sections on slides to remove excess reagents and to prevent non-specific binding during staining procedures.
Diluting antibodies: PBS is often used to dilute primary and secondary antibodies in immunohistochemistry (IHC) and immunofluorescence (IF) techniques.
Blocking solutions: PBS can be combined with bovine serum albumin (BSA) or other blocking agents to prevent non-specific binding of antibodies.
Cell culture: PBS is used to wash cells and tissues in culture to remove serum and other components before enzymatic dissociation or chemical treatments.

Advantages of Using PBS

There are several advantages to using PBS in histological applications:

Non-toxic: PBS is safe and non-toxic to cells and tissues.
Isotonic: The solution maintains osmotic balance, preventing cell lysis or shrinkage.
Stable pH: PBS maintains a stable pH environment, which is essential for preserving tissue morphology and protein function.
Versatile: PBS can be used in a variety of applications, from washing tissues to diluting reagents.

Limitations of PBS

Despite its many advantages, PBS also has some limitations:

Lack of nutrients: PBS does not provide any nutrients, so it is not suitable for long-term cell culture.
Calcium and magnesium free: Standard PBS lacks calcium and magnesium ions, which are important for certain cell functions.
Buffering capacity: The buffering capacity of PBS is limited, making it less effective in highly acidic or basic environments.

Alternatives to PBS

In some cases, other buffer solutions may be more appropriate for specific applications. Alternatives to PBS include:

Tris Buffered Saline (TBS): Often used in immunohistochemistry and Western blotting due to its higher buffering capacity.
Hanks' Balanced Salt Solution (HBSS): Contains additional ions and glucose, making it more suitable for cell culture applications.
Ringer's Solution: Contains calcium and magnesium, making it more physiologically relevant for certain applications.

Conclusion

Phosphate Buffered Saline (PBS) is an essential tool in histology and other biological research fields. Its non-toxic, isotonic properties make it ideal for washing tissues, diluting reagents, and maintaining cellular integrity. While it has some limitations, PBS remains a versatile and widely used buffer solution in various histological applications.