A facile dual-mode SERS/fluorescence aptasensor for AFB1 detection based on gold nanoparticles and magnetic nanoparticles

Aflatoxin B 1 (AFB 1 ) is a virulent metabolite secreted by Aspergillus fungi, impacting crop quality and posing health risks to human. Herein, a dual-mode Raman/fluorescence aptasensor was constructed to detect AFB 1 . The aptasensor was assembled by gold nanoparticles (AuNPs) and magnetic nanoparticles (MNPs), while the surface-enhanced Raman scattering (SERS) and fluorescence resonance energy transfer (FRET) effects were both realized. AuNPs were modified with the Raman signal molecule 4-MBA and the complementary chain of AFB 1 aptamer (cDNA). MNPs were modified with the fluorescence signal molecule Cy5 and the AFB 1 aptamer (AFB 1 apt). Through base pairing, AuNPs aggregated on the surface of MNPs, forming a satellite-like nanocomposite, boosting SERS signal via increased “hot spots” but reducing fluorescence signal due to the proximity of AuNPs to Cy5. Upon exposure to AFB 1 , AFB 1 apt specifically bound to AFB 1 , causing AuNPs detachment from MNPs, weakening the SERS signal while restoring the fluorescence signal. AFB 1 concentration displayed a good linear relationship with SERS/fluorescence signal in the range of 0.01 ng/mL–100 ng/mL, with a detection limit as low as 5.81 pg/mL. The use of aptamer assured the high selectivity toward AFB 1 . Furthermore, the spiked recovery in peanut samples ranged from 91.4 % to 95.6 %, indicating the applicability of real sample detection. Compared to single-signal sensor, this dual-signal sensor exhibited enhanced accuracy, robust anti-interference capability, and increased flexibility, promising for toxin detection in food safety applications.