Sterile 1x Phosphate-Buffered Saline (PBS) is a commonly used buffer solution in cell biology, biochemistry, and molecular biology research. It consists of a balanced salt solution containing sodium chloride, potassium chloride, sodium phosphate, and potassium phosphate. PBS helps maintain the osmolarity and pH of the solution, which is crucial for maintaining cell integrity and function during experiments.

To prepare sterile 1x PBS, you can either purchase ready-made sterile 1x PBS from a commercial supplier or prepare it yourself from a 10x PBS stock solution or individual components. Here’s a general protocol for preparing sterile 1x PBS:

1. If starting from a 10x PBS stock solution, dilute the stock solution 1:10 with distilled or deionized water. For example, to make 1 liter of sterile 1x PBS, mix 100 ml of 10x PBS stock solution with 900 ml of distilled or deionized water.
2. If preparing from individual components, weigh out the following salts to make 1 liter of 1x PBS:
   • 8 g of NaCl
   • 0.2 g of KCl
   • 1.44 g of Na2HPO4
   • 0.24 g of KH2PO4
   Dissolve the salts in approximately 800 ml of distilled or deionized water, and then adjust the pH to 7.4 using either HCl or NaOH.
3. After the salts are dissolved, and the pH is adjusted, bring the final volume to 1 liter with distilled or deionized water.
4. To make the 1x PBS solution sterile, filter-sterilize it using a 0.22 μm filter unit, or autoclave it at 121°C for 15-20 minutes.
5. Store the sterile 1x PBS at room temperature or 4°C for future use. Always check for any signs of contamination, such as cloudiness or particulates, before using the sterile 1x PBS in your experiments.

Sterile 1x PBS is widely used in cell culture for washing cells, diluting cells, and suspending cells for various assays. It is also used in molecular biology and biochemistry experiments for diluting samples, washing biomaterials, and as a buffer for immunostaining and other applications.