Phosphate Buffered Saline (PBS)

  • Phosphate buffered saline (PBS) is a buffer solution commonly used in biological research.
  • PBS is isotonic and non-toxic to cells. It is used in several applications of tissue culture, most notably for cell washing and trypsinization. These applications are dependent on the ability of PBS to maintain the cells in a viable and healthy state for a short duration.
  • PBS supports cell viability by keeping the medium pH and osmolality near-physiological.
  • Several formulations of PBS have been described. Most formulations contain similar amounts of sodium chloride and potassium chloride but differ in the concentration of Na2HPO4 and KH2PO4. PBS can also be supplemented with Calcium chloride and Magnesium chloride. Some of the PBS formulations are_ _ _ _
    • Sambrook’s PBS (1X) : 137 mM Sodium chloride, 2.7 mM Potassium chloride, 10 mM Disodium hydrogen phosphate, 1.8 mM Potassium dihydrogen phosphate
    • Dulbecco’s PBS (1X) : 137 mM Sodium chloride, 2.7 mM Potassium chloride, 8.1 mM Disodium hydrogen phosphate, 1.47 mM Potassium dihydrogen phosphate
  • PBS used for cell culture applications often do not contain calcium chloride and magnesium chloride but may contain glucose or pyruvate. Divalent cations inhibit trypsinization reaction (for subculturing). Glucose or pyruvate serves as an energy source and is added in PBS to keep the cells alive and healthy for a relatively long time.
  • PBS, used for immunocytochemistry/immunohistochemistry, is supplemented with divalent alkaline earth metals (calcium chloride and magnesium chloride). Divalent alkaline earth metals are helpful to ensure that uncondensed chromatin remains intact and contained within the nucleus during the staining procedure. It also dramatically decreases background fluorescence levels when using DNA probes excited by ultraviolet irradiation (DAPI and Hoechst).

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