Novel ultrasensitive homogeneous electrochemical aptasensor based on dsDNA-templated copper nanoparticles for the detection of ractopamine

Herein, we describe a novel homogenous electrochemical aptasensor for the ultrasensitive detection of ractopamine (RAC) based on the signal amplification of a hairpin DNA cascade amplifier (HDCA) and electrocatalysis of dsDNA-templated copper nanoparticles. The present electrochemical aptasensor employs a label-free turn-on'' strategy with enzyme-free amplification. Briefly, the target RAC triggers the HDCA autocatalytic process of two ingeniously designed complementary hairpin DNA, which results in the formation of nucleic-acid-stabilized copper nanoparticles (dsDNA/CuNPs). Thus, with the mimic oxidase catalytic character of the dsDNA/CuNPs and enzyme-free hairpin DNA cascade amplifier reactions, a remarkable electrochemical response can be achieved, which is dependent on the concentration of the target RAC. Taking advantage of the highly amplified efficiency of trigger recycling and the excellent electrochemical catalytic response of dsDNA/CuNPs, the proposed strategy is capable of detecting RAC ultrasensitively. Under optimal conditions, the electrochemical signal increases with an increase in the target RAC concentration in the wide dynamic range from 1 x 10(-12) M to 3 x 10(-7) M with a detection limit (LOD) of 3 x 10(-13) M. The proposed system does not need any sophisticated operation procedures such as electrode immobilization and expensive labeling. Therefore, the devised label-free and enzyme-free amplification homogeneous electrochemical aptasensor strategy may become an alternative method for the simple, sensitive, and selective detection of biological small molecules, proteins, nucleic acids and nuclease activity.