Ultrasensitive detection of aflatoxin B₁ by SERS aptasensor based on exonuclease-assisted recycling amplification

Aflatoxin B₁ (AFB₁) is one of the most abundant and carcinogenic food-contaminating mycotoxins around the world. In this study, we proposed a surface enhanced Raman scattering (SERS) sensing strategy for the determination of AFB₁. An aptamer for AFB₁ partially hybridized with complementary-DNA, which was released after the recognition of AFB₁ and immediately hybridized with hairpin DNA on the surface of sputtering Au film. Exonuclease III hydrolyzed the double-stranded DNA, leaving short single-stranded DNA on the Au surface and releasing complementary-DNA for next ring opening and digestion. SERS tag was captured on Au surface by DNA hybridization. Agarose gel electrophoresis and dynamic light scattering showed that SERS tag was successfully prepared. The detection principle was validated by electrochemical impedance spectroscopy and SERS at each step. High sensitivity and good selectivity for AFB₁ detection were observed. The results showed that there was a good linear relation when the AFB₁ concentration was from 1×10^-6 to 1ng/mL, and the limit of detection (LOD) was 0.4 fg/mL. This sensor was also applied for quantifying AFB₁ levels in spiked peanuts samples, the recoveries was in the range of 89-121%.