Distance-based lateral flow biosensor for the quantitative detection of bacterial endotoxin

Bacterial endotoxin (a type of lipopolysaccharide, LPS) that acts as the strongest immune stimulant exhibits high toxicity to human health. The golden standard detection methods rely heavily on the use of a large amount of tachypleus amebocyte lysate (TAL) reagents, extracted from the unique blue blood of legally protected horseshoe crabs. Herein, a cost-effective distance-based lateral flow (D-LAF) sensor is demonstrated for the first time based on the coagulation cascade process of TAL induced by endotoxin, which causes the generation of gel-state TAL. The gelation process can increase the amount of trapped water molecules and shorten the lateral flow distance of the remaining free water on the pH paper. The water flow distance is directly correlated to the concentration of endotoxin. Noteworthy, the D-LAF sensor allows the detection of endotoxin with the reduced dosage of TAL reagents than the golden standard detection methods. The detection limit of endotoxin is calculated to be 0.0742 EU/mL. This method can be applied to the detection of endotoxin in real samples such as household water and clinical injection solution with excellent performance comparable to the commercial ELISA kit.