A SERS and Fluorescence Dual-Signal Aptasensor for AFB₁ Detection Based on DTNB Labeled AuNPs and CdTe Quantum Dots

Herein, an aptasensor with stable surface-enhanced Raman scattering (SERS) and fluorescence dual-signal output had been developed for the detection of aflatoxin B₁ (AFB₁). The quantum dots were encapsulated within silica to ensure the stability of fluorescence signal. The gold nanoparticles (AuNPs) were modified with SERS signal molecule DTNB and the complementary sequence (cDNA) of AFB₁ aptamer and then connected on the surface of silica to obtain the signal probes. In the meantime, Fe₃O₄ was coated with silica which was modified with aptamer to gain capture probes. The two probes could bind specifically based on the base complementary pairing principle. Then, the mixture was separated and gathered by an external magnet. At this time, the maximum SERS signal could be detected in the precipitate, and there was no fluorescence signal in the supernatant. Upon introduction of AFB₁ into the system, the signal probes would be released, resulting in fluorescence recovery in the supernatant while SERS signal weakened in the precipitate. The developed method showed a linear relationship of AFB₁ for the SERS signal in the range of 10⁻⁴–10³ ng/mL, with a detection limit of 0.087 pg/mL. The linear range for the fluorescence signal was from 10⁻⁴ to 10² ng/mL, with a detection limit of 0.100 pg/mL. The proposed technique was highly sensitive and accurate, which showed promising application prospects in food safety detection.