What is Phosphate Buffered Saline (PBS)?
Phosphate Buffered Saline (PBS) is a widely used buffer solution in biological research. It is a water-based salt solution containing sodium chloride, sodium phosphate, and, in some formulations, potassium chloride and potassium phosphate. Its primary function is to maintain a constant pH and osmotic balance, which is critical for many biological processes.
Why is PBS Used in Histology?
In
histology, PBS is frequently used for its buffering capacity and isotonic nature, which ensures that tissues and cells are not damaged or altered during processing. PBS is particularly important in
immunohistochemistry, where it is used to wash and rehydrate tissue sections to maintain the integrity of
antigens and other cellular components.
How is PBS Prepared?
PBS can be prepared by dissolving premeasured tablets or powder in
distilled water. The typical composition includes 137 mM sodium chloride, 2.7 mM potassium chloride, and 10 mM phosphate buffer, at a pH of approximately 7.4. The final solution can be sterilized by autoclaving or filtration.
Stability: PBS maintains a stable pH, which is crucial for preserving tissue morphology and antigenicity.
Isotonicity: Being isotonic, PBS prevents cell lysis and shrinkage, which can occur with non-isotonic solutions.
Compatibility: PBS is compatible with a wide range of biological assays and staining protocols.
Are There Any Alternatives to PBS?
While PBS is highly versatile, other
buffer solutions such as Tris-buffered saline (TBS) and HEPES-buffered saline can be used depending on specific experimental requirements. However, PBS remains the most commonly used buffer in histology due to its simplicity and effectiveness.
Common Applications of PBS in Histology
In histology, PBS is used in several key applications: Washing: PBS is used to wash tissue sections to remove excess reagents and prevent non-specific staining.
Rehydration: Tissue sections are often rehydrated in PBS after being deparaffinized and rehydrated through a graded alcohol series.
Antibody Dilution: In immunohistochemistry, antibodies are often diluted in PBS to ensure uniform binding and reduce background noise.
Potential Issues and Troubleshooting
While PBS is generally reliable, certain issues can arise: Precipitation: If not properly mixed or stored, salts in PBS can precipitate, which can interfere with staining and assays.
pH Variability: Improper preparation can result in pH variability, which can affect tissue integrity and staining results.
To avoid these issues, always use freshly prepared or properly stored PBS, and ensure it is mixed thoroughly before use.
Conclusion
Phosphate Buffered Saline is an indispensable reagent in histology, offering a stable, isotonic environment for tissue processing and staining. Its versatility and reliability make it a cornerstone in both routine histological procedures and advanced research applications.
