A core-satellite self-assembled SERS aptasensor used for ultrasensitive detection of AFB₁

A surface-enhanced Raman scattering (SERS) aptasensor was developed using gold nanostars (Au NSs) and Fe₃O₄@Au nanoparticles (NPs) for the highly sensitive detection of aflatoxin B₁ (AFB₁). Au NSs were modified by the Raman reporter 4-aminothiophenol (PATP) and then coupled with cDNA to act as the capture probes (Au NSs@PATP-cDNA). Fe₃O₄@Au NPs were modified with the AFB₁ aptamer (AFB₁ Apt) and used as signal probes (Fe₃O₄@Au NPs-AFB₁ Apt). The SERS peak of PATP at 1078 cm^-1 was used for quantitative analysis. When the core-satellite nanostructures (Fe₃O₄@Au NPs-AFB₁ Apt/cDNA-Au NSs@PATP) were self-assembled by oligonucleotide hybridization, the SERS intensity was significantly enhanced. When AFB₁ was present, AFB₁ Apt specifically binds to AFB₁, causing the Fe₃O₄@Au NPs-AFB₁ Apt and Au NSs@PATP-cDNA to dissociate, resulting in a decrease in the SERS intensity measured after magnetic separation. Under optimal conditions, the limit of detection (LOD) of AFB₁ can be reduced to 0.24 pg/mL. This is attributed to the high affinity of AFB₁ Apt, excellent magnetic separation characteristics, and multiple SERS hotspots. The assay has been validated to perform well in recovery and accuracy by evaluating spiked samples (rice, corn, and wheat) and positive samples (corn, brown rice, and wheat).