Endotoxin/LAL – USP (85)

Nova is an industry leader in microbiology testing & pharmaceutical testing, providing Endotoxin Testing services to detect and quantify gram-negative bacterial endotoxins.

Our services are used worldwide by leading pharmaceutical and medical device companies to ensure the safety of their parenteral drugs, biological products, and medical devices.

The LAL Test Limulus amebocyte lysate (LAL) is an aqueous extract of blood cells (amebocytes) from the horseshoe crab, Limulus polyphemus. LAL reacts with bacterial endotoxin or lipopolysaccharide, which is a membrane component of gram-negative bacteria. This reaction is the basis of all three of Nova’s LAL test methodologies: gel-clot, turbidimetric, and chromogenic. The primary application for LAL is the testing of parenteral pharmaceuticals and medical devices that contact blood or cerebral spinal fluid. All of Nova’s reagents and instrumentation are manufactured by Associates of Cape Cod, the first manufacturer licensed by the FDA to produce LAL.

Gel-clot Method

The gel-clot method is the simplest and most widely used LAL test. The reaction in the test tube is essentially the same as that in nature when a horseshoe crab is injured. The gel-clot test is the compendial method. It is the only endotoxin test fully described in the United States Pharmacopoeia (USP) and many other pharmacopeias, though other methods are permitted as alternatives.

Turbidimetric Methods

As the concentration of insoluble coagulin increases during the LAL reaction, the turbidity of the reaction mixture increases. The rate at which turbidity increases is related to the endotoxin concentration in the sample and is the basis of the Turbidimetric methods. There are two variations of the Turbidimetric methods; Endpoint Turbidimetric Method and Kinetic Turbidimetric Method.

Chromogenic Methods

Chromogenic methods utilize a synthetic substrate which is added to the lysate. The reagent used by Nova has the substrate co-lyophilized with the LAL reagent, which enables it to be used for all chromogenic methods. When chromogenic LAL reagent reacts with endotoxin, the cascade is initiated, and clotting enzyme is activated as in the other methods. The reactions proceed more rapidly at higher endotoxin concentrations. There are three variations of the chromogenic test; two Endpoint Chromogenic Methods and Kinetic Chromogenic Method.

Turbidimetric Method

The turbidimetric method is similar to the chromogenic method. It can be used for a wide variety of endotoxin tests, ranging from standard water testing to samples requiring high sensitivity, such as intrathecal products and those requiring high dilutions to overcome interference. The maximum sensitivity is 0.005 EU/mL.

Choosing The LAL Test Method

Most samples can be tested by any of the methods. However, for some samples, one method is preferable to the others. If you need help in the selection of a suitable test method, our technical service representatives at Nova are always available to help.

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