Phosphate-buffered saline (PBS)
Phosphate-buffered saline (PBS) is a buffer solution commonly used in biological research to maintain physiological pH and osmolarity, supporting cell viability and protein stability during experiments such as cell washing, dilution, and storage.
What is phosphate-buffered saline (PBS)?
Phosphate-buffered saline (PBS) is a widely used aqueous buffer solution in molecular biology, cell culture, and immunology. It maintains a stable pH of approximately 7.4, closely matching human physiological conditions, and has an osmolarity of around 300 mOsm/L. PBS is composed of sodium chloride, potassium chloride, sodium phosphate, and potassium phosphate, with the exact concentrations adjusted to achieve the desired buffering capacity and ionic strength.
Why is PBS used in laboratory procedures?
PBS is employed for a variety of applications, including washing cells, diluting reagents, preparing samples for microscopy, and equilibrating chromatography columns. Its neutral pH and isotonic nature prevent cell lysis or shrinkage, making it ideal for handling live cells or sensitive biomolecules. PBS is also used in ELISA, Western blotting, and flow cytometry to minimise non-specific binding and preserve protein conformation.
Are there variations of PBS?
Yes, several variants exist. PBS without calcium and magnesium (Ca²⁺/Mg²⁺-free PBS) is used when chelating agents are required or when avoiding enzyme activation. Modified formulations may include additives such as bovine serum albumin (BSA) or EDTA for specific applications. Some protocols use PBS with added glucose or other stabilisers for long-term storage.
Related concepts
Commonly used alongside PBS are other buffers such as HEPES and Tris, and solutions like PBS-T (PBS with Tween-20) for reducing background in immunoassays. PBS is also referenced in regulatory standards including USP, EP, and ISO for quality control in pharmaceutical and diagnostic product testing.