Novel label-free fluorescence aptasensor for chloramphenicol detection based on a DNA four-arm junction-assisted signal amplification strategy

A novel label-free fluorescence aptasensor was established for chloramphenicol (CAP) detection by DNA four-arm junction-assisted target recycling and SYBR Green I dye-aided fluorescence-signal amplification. The CAP aptamer was hybridized to its complementary strand (primer) to form a double-stranded primer/aptamer complex. In the presence of CAP, aptamers can specifically bind with CAP to dissociate primers, which can trigger the self-assembly of four hairpins to continuously generate DNA four-arm junctions. After digesting the excess hairpins using T7 exonuclease, SYBR Green I was inserted into the base pair-rich DNA four-arm junctions, which led to a significant increase in fluorescence intensity. Under optimal conditions, the developed aptasensor can detect CAP in a linear range of 1.0 pg mL−1 to 10 ng mL−1 with a detection limit of 0.72 pg mL−1. The recovery rates in milk and honey ranged from 90.3% to 106.6%. Thus, the method shows substantial potential for CAP detection in food products.