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 Fe2O3 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 Cu2+, 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.