Most commercially available antibodies contain small amounts of preservatives such as sodium azide to prevent microbial growth. However, sodium azide is also toxic to mammalian cells as it inhibits cellular respiration. Actual toxicity varies by cell type with neuronal cells being most sensitive. Toxicity is concentration, time, and temperature dependent. For most cell sorting experiments the health of cells are not impacted because the antibody is diluted and cells are typically incubated on ice for less than one hour.

For experiments where cells will be incubated with antibodies over several hours or days, sodium azide free formulations are recommended. Antibodies can be purchased in this formulation or sodium azide can be removed by dialysis. However it is important to note that these antibodies will be significantly more susceptible to microbial contamination. If they are purified they can be aliquoted and frozen.


Ishikawa T, et al. "Effect of sodium azide on the metabolic activity of cultured fetal cells." Toxicol Ind Health 22.8 (2006): 337-341. PubMed