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 ofLPS 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 495/543nm. The probe responds to LPS in the 10-500ngmL(-1) concentration range, and the detection limit is 8.7ngmL(-1). It can be used for selective detection of LPS from different Gram-negative bacteria, in the presence of biological interferents.Schematic presentation of a greenfluorescent probe comprised of an aptamer labelled withCdSe/ZnS quantum dots and ofgraphene oxide. Lipopolysaccharides bind to the aptamer and release graphene oxide to result in fluorescence recovery, which is measured at anemission wavelength 543nm.