What is the Origin of LAL Assay?

The assay is named after the Limulus polyphemus, the horseshoe crab, whose blood contains amebocytes that are exquisitely sensitive to bacterial endotoxin. The lysate, an extract from these amebocytes, forms a clot in the presence of trace amounts of LPS. This biological principle was adapted into a standardized test, offering a rapid and reliable method for pyrogen detection that replaced the older, less sensitive rabbit pyrogen test.

What is the Mechanism of LAL Assay?

The mechanism is based on an enzyme cascade found within the horseshoe crab amebocytes. Upon contact with LPS, the endotoxin activates a proenzyme, factor C, which subsequently activates factor B, leading to the cleavage of proclotting enzyme to clotting enzyme. The clotting enzyme then catalyzes the formation of a protein coagulin clot from a coagulogen substrate. Modern variations of the assay often use synthetic substrates that produce a measurable color change or turbidity, allowing for precise spectrophotometric quantification of the endotoxin concentration.

LAL Assay ∞ Area

LAL Assay

Meaning

The LAL Assay, or Limulus Amebocyte Lysate Assay, is a highly sensitive and specific in vitro test used clinically and industrially to detect and quantify the presence of bacterial endotoxins, specifically lipopolysaccharides (LPS) from the outer membrane of Gram-negative bacteria. Endotoxins are potent pyrogens, meaning they can cause fever and systemic inflammatory responses in humans, making their absence critical for the safety of injectable pharmaceuticals, medical devices, and hormone preparations. This assay is a cornerstone of quality control in pharmaceutical compounding and manufacturing.