Phosphate buffered saline (PBS) is a balanced salt solution commonly used in cell culture and immunofluorescene studies. But what is the purpose of PBS?
The purpose of PBS is to maintain the 1) constant pH and the 2) osmolarity of the cells. The pH of most biological materials fall between 7 to 7.6. For instance, pH of cytosol is 7.2 while the pH of mitochondrial matrix is 7.5. The pH of PBS is set to be 7 to 7.6, so it can maintain the constant pH of the cells that you are working with. Other than this, PBS also has the same osmolarity of the body (isotonic).