A novel fluorescent aptasensor for ultrasensitive detection of microcystin-LR based on single-walled carbon nanotubes and dapoxyl

To assure water safety and protect human health, precise and simple analytical approaches are highly desired to determine low concentrations of microcystin-leucine-arginine (MC-LR), a toxin, in both water and serum samples. Herein, a simple, rapid and accurate aptamer-based fluorescent sensor was used for selective recognition of MC-LR, based on single-walled carbon nanotubes (SWNTs) as immobilizers, dapoxyl as a fluorescent dye, DAP-10 as a specific aptamer for dapoxyl and unmodified MC-LR aptamer (Apt) as a sensing ligand. The sensing method was developed to produce a remarkable fluorescence intensity difference in the absence and presence of MC-LR. Moreover, the Apt was used without any modification. In the absence of MC-LR, the dapoxyl could bind to DAP-10, leading to a strong fluorescence intensity. In the presence of MC-LR, DAP-10 bound to the surface of SWNTs, resulting in a very weak fluorescence intensity. Under optimized conditions, the presented fluorescent analytical approach showed high selectivity toward MC-LR with a limit of detection (LOD) of 138 pM. This new method indicated excellent analytical performance for MC-LR detection in tap water and serum samples with LODs of 135 and 168 pM, respectively.