A label-free and enzyme-free fluorescent aptasensor for sensitive detection of acetamiprid based on AT-rich...

A label-free and enzyme-free aptasensor for sensitive assay of acetamiprid has been established using AT-rich double-stranded (ds) DNA-templated copper nanoparticles (CuNPs) as fluorescent probe. In this work, two hairpin DNA, HP1 and HP2, were elaborately designed with AT-rich DNA sequences in their loops. The aptamer of acetamiprid was located at the 3'-terminal of HP1, which was caged in the stem of HP1. Upon the addition of acetamiprid, the aptamer could combine with acetamiprid to form a target/aptamer complex, and thus its free 5'-terminal was released. Subsequently, the protruded 3'-terminal of HP2 could hybridize with the free 5'-terminal of HP1 to form a stable AT-rich dsDNA. When it interacted with Cu²⁺ and ascorbic acid (AA), the AT-rich dsDNA/CuNPs were generated with strong fluorescence, offering a "switch-on" detection of acetamiprid. The developed strategy could high selectively detect acetamiprid at the concentration as low as 2.37 nM. Moreover, the possibility of this strategy for the food sample analysis was also investigated. The obtained results demonstrate that the developed strategy has a promising application potential for acetamiprid assay in food safety fields.