Limulus Amebocyte Lysate

What is Limulus Amebocyte Lysate?

LAL is a reagent made from the blood of the horseshoe crab. In the presence of bacterial endotoxins, the lysate reacts to form a clot or causes a color change. The Limulus Amebocyte Lysate (LAL) test is also called the Bacterial Endotoxins Test (BET), or sometimes is referred to as the pyrogen test as bacterial endotoxins can cause a fever in mammals, including humans. This test is an in vitro assay for the detection and quantitation of this germ-negative bacteria within a cell wall.

What Is Bacterial Endotoxins Test?

The BET is performed as a lot release test for the evaluation of medical devices coming in contact with the cardiovascular system, lymphatic system, or cerebrospinal fluid. This determines the presence of bacterial endotoxins by testing the blood cells of horseshoe crabs to identify pyrogenic responses. Bacterial endotoxin testing (LAL) is required for any product that comes in direct or indirect contact with intravascular, intralymphatic, intrathecal, and intraocular systems to ensure that the product’s endotoxin content is under the allowable release limit value. The endotoxin limit for medical devices is less than 20.0 EU/device unless the device will have contact with cerebrospinal fluid, the limit for the device will have contact with the cerebrospinal fluid is 2.15 EU/device. Ophthalmic implants may even be required to meet a lower limit of 0.2 EU/device.

Applicable Standards

Both the FDA Guidance for Industry Pyrogen and Endotoxins Testing, the USP <85>, USP<161> give out guidance for conducting BET studies.

Testing Methods

There are three methods for the Bacterial Endotoxins test: the kinetic turbidimetric, kinetic chromogenic, and gel-clot test methods. And the kinetic test methods have significant advantages over the gel-clot method. For the kinetic turbidimetric method, a tube reader or 96 well-plate reader is used to monitoring the change in a solution’s clarity as a result of the presence of endotoxin. The time of the solution changes is negatively correlated with the concentration of endotoxin in the test sample. The reaction time of the sample is used to calculate endotoxin concentration by comparing it to a standard curve. For the kinetic chromogenic method, the change is monitored in a solution’s color. The time of the solution to turn yellow is negatively correlated with the concentration of endotoxin. A fixed time frame and intensity of the color are used to distinguish the endotoxin level. For the gel-clot method, mixing the gel clot LAL and equal amounts of the test material and then incubating. After incubation, the tube is inverted. If endotoxin is present, the solution will clot and gel will remain at the bottom of the tube.

STEMart offers Limulus Amebocyte Lysate Testing services in various standards, if you have additional questions about Limulus Amebocyte Lysate Testing or would like to find out more about our services, please feel free to contact us.