Bidirectional hybridized hairpin DNA fluorescent aptasensor based on Au–Pd NPs and CDs for ratiometric detection of AFB1

A novel and simple ratiometric fluorescent aptasensor was developed for the sensitive detection of aflatoxin B1 (AFB1). A hairpin DNA (h-DNA) was independently synthesized as the basic skeleton, and the bidirectional hybridization of h-DNA can increase the load of aptamer and signal probes, thereby realizing signal amplification. The high-efficiency fluorescence resonance energy transfer interaction between gold–palladium nanoparticles (Au–Pd NPs) and the self-synthesized fluorescent probe carbon dots (CDs) was utilized. Moreover, the label-free probe SYBR Green I (SG I) dye was introduced to form a double-signal probe with CDs, and a ratiometric sensor with F_CDs/F_{SG I} as a response signal was constructed. The ratio strategy can eliminate the fluctuation of external factors, thus improving the accuracy and reliability of the sensor. The quenching effect of Au–Pd NPs on CDs was 1.4 times that of AuNPs and 3.4 times that of Pd NPs, respectively. In the range 1–100 ng/mL, F_CDs/F_{SG I} showed a good linear relationship with the logarithm of the concentration of AFB1, and the limit of detection was as low as 0.07 ng/mL. The sensor was used to detect AFB1 in spiked peanuts and wine samples, and the recovery was between 91 and 115%, indicating that the sensor has high application potential in real sample analysis.

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