A fluorescent probe composed of quantum dot labeled aptamer and graphene oxide for the determination of the lipopolysaccharide endotoxin

Endotoxins are complex lipopolysaccharides (LPS) and key components of the outer cell membrane of Gram-negative bacteria. The authors report on a fluorescent aptamer-based probe for the determination of LPS of Gram-negative bacteria. An aptamer against LPS was fluorescently labeled with CdSe/ZnS quantum dots. Its emission is quenched on addition of graphene oxide (GO). On addition of LPS, the aptamer binds LPS and GO is released. This results in the recovery of fluorescence, typically measured at excitation/emission wavelengths of 495/543 nm. The probe responds to LPS in the 10–500 ng·mL−1 concentration range, and the detection limit is 8.7 ng·mL−1. It can be used for selective detection of LPS from different Gram-negative bacteria, in the presence of biological interferents.