Endotoxins are lipopolysaccharides from Gram-negative bacterial cell walls. Even nanogram amounts activate immune cells in culture, so a contaminated reagent can produce results that have nothing to do with the peptide.
How the LAL assay works
The Limulus amebocyte lysate test uses a clotting cascade from horseshoe crab blood that is triggered by endotoxin. Gel-clot, turbidimetric and chromogenic formats report results in endotoxin units (EU) per mg.
When to ask for endotoxin data
- Macrophage, monocyte or dendritic cell assays
- Cytokine readouts
- Primary cell cultures
Reducing contamination in the lab
Use endotoxin-free tubes and tips, sterile diluents and aseptic technique when reconstituting and aliquoting.
