The LAL assay is the most sensitive method for the detection of bacterial endotoxins currently approved by the FDA. The first methodology used to determine the LAL test results was the formation of a gel-clot in the bottom of a glass reaction tube. It has also been observed that the test solution becomes turbid prior to gel-formation. The time required to produce a specified level of turbidity is inversely proportional to the amount of endotoxin in a sample.
A photometric instrument such as the Toxinometer™ (Wako Pure Chemical Industries, Ltd.) is used to measure the rate of turbidity change. This quantitative measurement procedure is often referred to as the Kinetic Turbidimetric Assay (KTA).
By utilizing these properties, Wako Chemicals USA has developed a unique LAL endotoxin test that can be used either as a quantitative turbidimetric test or as a qualitative gel-test.
PYROSTAR™ ES-F/Plate is intended for the quantitative detection of endotoxins by kinetic turbidimetric using a microplate reader. The quantitative range for the Kinetic Turbidimetric Assay (KTA) is 0.01 to 10EU/mL.
The Microplate Reader is used in place of the Toxinometer to obtain KTA results of PYROSTAR™ ES-F Multi products.
PYROSTAR™ ES-F is intended for the qualitative detection of endotoxins by gel-clot or the quantitative detection of endotoxins by kinetic turbidimetric methods. The quantitative range for the Kinetic Turbidimetric Assay (KTA) is based on the lysate gel-clot labeled sensitivity, refer to the table below:
|Gel-clot Labeled Lysate Sensitivity (EU/mL)||KTA Quantitative Range (EU/mL)|
|0.015||0.001 to 10|
|0.03 to 0.25||0.01 to 10|
The specificity of LAL is not absolute. It has been reported that LAL reacts not only with endotoxin by also with β-1, 3-glucan. Although the cascade system activated by β-1,3-glucan has been shown to be different than the one activated by endotoxin, the end result, gel-clot formation is indistinguishable.
The activation of LAL by glucan in a sample can be prevented by adding a large amount of carboxymethylated curdlan (CMC) to LAL. The presence of large amounts of glucan does not interfere with the quantitation of endotoxin. Wako first made use of these findings by developing an ES-buffer, which contains high concentrations of CMC. When the ES-buffer is used to reconstitute LAL, the LAL reagent becomes endotoxin-specific. PYROSTAR™ ES-F is a new preparation of LAL in which CM-curdlan is co-lyophilized with LAL. Reconstituting PYROSTAR™ ES-F vials with sample, results in an endotoxin-specific LAL reagent for the specific determination of gram negative bacterial endotoxins without interference from the presence of glucans in the sample.