Preparation of Stock Solution of G-418 (100 mg/ml in water)

OVERVIEW

G-418 (also called G418, or G 418) is a selective antibiotic that is effective against many live organisms including bacteria and mammalian cells. It is extensively used in cell culture to generate a cell line stably expressing a gene of interest.

A stock solution of 100 mg/ml is prepared by dissolving 1 g of G-418 disulfate salt in the Milli-Q water to a final volume of 10 ml. The solution is sterilized by filtering through a 0.2 µ filter unit. The stock solution is diluted to achieve the final concentration which is usually between 200 – 600 µg/ml for most mammalian cell lines. 

REQUIREMENTS

Reagents
G-418 disulfate salt (e.g., ThermoFisher Scientific #11811031)
Deionized / Milli-Q water 

Equipment and disposables 
Falcon® screw cap graduated Conical Tubes, 15 mL (e.g., SARSTEDT, 62.554.502)
Syringe filter unit, 0.2 µ (e.g., SARSTEDT, 83.1826.001)

Composition: 
100 mg/ml G-418 in water

Objective
Preparation of 10 ml of 100 mg/ml G-418 solution in water

PREPARATION

Step 1: Weigh out 1 g G-418 sulfate salt and transfer to a 15 ml Falcon conical tube. Add 8 ml Milli-Q water. Tighten the cap and dissolve G-418 by inverting the tube several times. 

Note: G-418 sulfate salt dissolves quickly in water. Generally inverting the tube a few times is sufficient to dissolve it.

Step 2: Adjust the volume to 10 ml with Milli-Q water. Mix by inverting the tube a few times. 

Step 3: Sterilize the solution by filtering through a filter unit containing 0.2 µ filter paper. 

Note: Filter sterilization removes all suspended particles with a size of more than 0.22 μ which includes most bacteria and their spores but not mycoplasma. However, it does not inactivate enzymatic activities (e.g., DNases).

Storage: 
The solution can be stored at -20°C for a year in small aliquots (0.5 ml or 1.0 ml). The solution can also be stored for a month at 4°C.

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