Bacterial endotoxin refers to a complex of lipopolysaccharide and protein on the cell wall of Gram-negative bacteria. Endotoxins are released after bacterial death or autolysis. Endotoxins entering the blood in large amounts can cause a fever reaction - 'pyrogenic reaction'. The bacterial endotoxin test method uses limulus reagent to detect or quantify bacterial endotoxins produced by Gram-negative bacteria to determine whether the endotoxin limits in the sample comply with regulations. The principle is that endotoxin activates factor C in the limulus reagent, causing the limulus reagent to undergo a series of enzyme-linked reactions, eventually forming a gel or activating the coagulase and adding a chromogenic group to detect bacterial endotoxin content. The main detection methods are divided into gel method and photometric method.
The gel method is mainly used for the qualitative and semi-quantitative determination of endotoxins. Although it is a standard method for endotoxin detection, the detection range is limited and there are requirements for detection water and detection conditions.
Photometric methods are further divided into turbidity methods and chromogenic matrix methods. Turbidity methods include dynamic turbidity methods and end-point turbidity methods. Chromogenic matrix methods are divided into dynamic chromogenic methods and end-point chromogenic methods, which can quantitatively detect endotoxin content.
turbidity method reacts with factor C of endotoxin and limulus reagent, and the activated coagulase will cut off the arginine peptide chain in the coagulogen, forming a gel-like protein; while the chromogenic matrix method is a limulus test that detects endotoxin content by measuring the amount of chromophore released from a special substrate by the coagulase produced when endotoxin reacts with limulus reagent. Gel method vs photometric method