The Limulus Amebocyte Lysate, or LAL, assay is a widely used method for detecting bacterial endotoxin. The assay uses lysate derived from horseshoe crab amebocytes to detect endotoxin through a sensitive enzymatic cascade reaction.
LAL-based endotoxin testing can be performed using several different assay formats, including gel-clot, kinetic turbidimetric and chromogenic methods.
Gel-Clot Method
The gel-clot method determines the presence or absence of endotoxin according to the formation of a firm gel after incubation. It is a simple and widely used qualitative or semi-quantitative approach.
Kinetic Turbidimetric Method
The kinetic turbidimetric method determines endotoxin concentration by continuously monitoring the increase in turbidity during the reaction.
Chromogenic Methods
Chromogenic LAL assays use a chromogenic substrate to generate a measurable color response. Depending on the assay design, the method can provide quantitative endotoxin results.
The appropriate LAL assay format should be selected according to the sample, required sensitivity, testing workflow and analytical requirements.
Reliable LAL Testing
Reliable results depend not only on the lysate reagent but also on endotoxin-controlled water, appropriate consumables, correct sample preparation, suitable controls and proper incubation and detection conditions.