Endotoxin testing (LAL)


The Limulus Amebocyte Lysate (LAL) test is a method for the detection and quantitation of endotoxins. Endotoxins are biologically active molecules that are found in the outer cell membrane of all Gram-negative bacteria. These molecules contain a hydrophilic polysaccharide and a lyophilic lipid part (lipid A) collectively called Lipopolysaccharide (LPS). Bacterial endotoxins are known to cause fevers and disease when injected into the bloodstream. Unlike bacteria, endotoxins are difficult to remove as they are heat and pH stable, and toxicity is not dependent on the presence of the bacterial cell.

The LAL test uses components found in the blood cells (amebocytes) of the blue horseshoe crab (Limulous polyphemus), which forms a gel-like clot when incubated in the presence of endotoxins. This in vitro chromogenic method is used to determine whether products or materials are free of endotoxin contamination. The sensitivity or detection limit of this test is 0.2 EU/ml (Endotoxin Units). 

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