Gentamicin is an aminoglycoside antibiotic. It is effective against a wide variety of aerobic bacteria including E. coli. A 50 mg/ml stock solution of gentamicin can be prepared by dissolving 50 mg in 1 ml deionized water. Solution is sterilized by filtering through 0.2 µ filter unit.
Gentamicin sulfate salt (e.g., Sigma-Aldrich #G1264)
Deionized / Milli-Q water
50 mg/ml gentamicin in water
Preparation of 10 ml of 50 mg/ml gentamicin solution
Step 1: Weigh out 500 mg Gentamicin sulfate salt and transfer to a 15 ml Falcon conical tube. Add 8 ml deionized / Milli-Q water. Tighten the cap and dissolve gentamicin by inverting the tube several times.
Note: Gentamicin sulfate salt dissolves quickly in water. Generally inverting the tube a few times is sufficient to dissolve Gentamicin sulfate salt. Alternatively, one can use a tube rotator to dissolve it.
Step 2: Adjust the volume 10 ml with deionized / 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).
The solution can be stored at -20 °C for several months in small aliquots (0.5 ml or 1.0 ml).