Magnetic ratiometric SERS aptasensor based on Au (Core)-internal standard-Ag (shell) structure for patulin quantitative detection

As a major contaminant in apples, patulin (PAT) poses a significant threat to human health and the economy. Establishing highly sensitive and accurate quantitative detection methods for PAT is crucial for ensuring food safety and protecting consumer health. Herein, a competitive ratiometric surface-enhanced Raman spectroscopy (SERS) aptasensor was fabricated. 4-Mercaptobenzoic acid (4-MBA) was embedded as an internal standard (IS) within a gold-silver core-shell structure, later assembled onto Fe 3 O 4 nanoparticles and coupled with complementary aptamer strands to form magnetic probes. Additionally, an aptamer targeting PAT and the Raman reporter molecule 5,5′-Dithiobis-(2-nitrobenzoic acid) (DTNB) were anchored onto gold bipyramids (AuBPs), creating reporter probes. The recognition and binding of the target PAT to the aptamer led to the detachment of the reporter probe after magnetic separation, reducing the DTNB signal. Thus, the ratio of SERS peak intensities (I DTNB /I 4-MBA ) quantified PAT demonstrated a linear range of 0.1–200 ng/mL and a limit of detection (LOD) of 0.070 ng/mL. The implementation of magnetic separation significantly streamlined the sensor fabrication process, whereas the ratiometric strategy substantially enhanced the reproducibility and stability of PAT detection. Furthermore, this method was successfully applied to the determination of PAT in apples and their products, showing potential for practical applications in food safety.