A zero-background fluorescent aptasensor for ultrasensitive detection of pesticides based on magnetic three-dimensional DNA walker and poly(T) -templated copper nanoparticles

A zero-background fluorescent aptasensor for the ultrasensitive detection of pesticides has been successfully constructed, using poly(T) stabilized copper nanoparticles (CuNPs) as a fluorescent signal and three-dimensional (3-D) DNA walker as a signal amplifier. To fabricate the aptasensor, one strand of dsDNA and one strand of ssDNA are immobilized onto magnetic Fe 2 O 3 beads. The dsDNA is hybridized by the target aptamer contained DNA (Apt-1) and the partial complementary DNA which named as WS since it acts as a walking strand (WS) in DNA walker. Upon the specific binding between omethoate with Apt-1, WS becomes a free walking ssDNA strand. With the aid of nicking endonuclease, the 3-D DNA walker can produce a great quantity of poly(T) DNA during the WS walking. When the supernatant is added into ascorbic acid (AA) and Cu 2+ , poly(T) templated CuNPs forms and strong fluorescence generates. The developed aptasensor has a zero-background, and can ultrasensitively detect omethoate in the linear range of 0–200 nM with the detection limit of 0.22 nM. This zero-background aptasensor provides a facile strategy for pesticides determination in the fields of food safety and environmental monitoring.