Phosphate-buffered saline (PBS) is a buffer solution frequently used in pharmaceutical practice, particularly in the formulation of ophthalmic solutions. It is also used in colorimetric determination of pH and in research studies where maintaining a constant pH is essential.

Phosphate-buffered saline (PBS) contains sodium chloride (NaCl) and dibasic sodium phosphate (Na₂HPO₄). It may also contain potassium chloride (KCl), monobasic potassium phosphate (KH₂PO₄), calcium chloride (CaCl₂), and magnesium sulfate (MgSO₄).

Formula for Preparing Phosphate-Buffered Saline (PBS)

There are several variations in the formula for preparing PBS. Two common examples follow:

Formula One: Take 8 g NaCl, 0.2 g KCl, 1.44 g Na₂HPO₄, and 0.24 g KH₂PO₄ in 800mLdistilled water. Adjust pH to 7.4 using HCl. Add sufficient (qs ad) distilled water to achieve 1 liter.

Formula Two: Another variant of PBS. This one is designated as “10X PBS(0.1 M PBS, pH7.2)” since it is much more concentrated than PBS and the pH is not yet adjusted to pH 7.4. Take 90 g NaCl, 10.9 g Na₂HPO₄, and 3.2 g NaH₂PO₄ in 1000 mL distilled water. Dilute 1:10 using distilled water and adjust pH as necessary.

Applications of Phosphate Buffered Saline in Research

Phosphate Buffered Saline serves numerous roles in biological and medical research:

• Cell Culture: PBS is frequently used to wash cells during culturing, as it maintains cell viability without disrupting the cellular environment.
• Immunoassays (e.g., ELISA, Western Blotting): It is used for washing plates and diluting antibodies.
• Tissue Processing: PBS helps in rinsing and preserving tissue samples prior to analysis or staining.
• Molecular Biology: It’s used in DNA and RNA purification procedures to maintain pH and salt conditions.

PBS is essential because it maintains a stable pH and isotonic environment, reducing cell stress and preserving biological function.

Advantages of Using Phosphate Buffered Saline

There are several reasons why PBS is preferred in many laboratory settings:

• Non-toxic and Physiological: It is isotonic and non-toxic to most cells, making it safe for in vitro and ex vivo use.
• Buffer Capacity: PBS maintains a consistent pH, which is crucial for experiments involving enzymes and antibodies.
• Compatibility: PBS is compatible with most biochemical and cell-based assays, which increases its utility across different protocols.

Reference:

• Sinko, P. (2011). Martin’s Physical Pharmacy and Pharmaceutical Sciences. Baltimore, : Lippincott Williams & Wilkins, a Wolters Kluwer business.