An aptamer sensor based on AgNPs@MOF for surface-enhanced Raman spectroscopy detection of sulfadimethoxine in food

A highly sensitive aptamer sensor (aptasensor) is proposed based on metal–organic frameworks-silver nanoparticles (AgNPs@MOF) to detect sulfadimethoxine (SDM) by surface-enhanced Raman spectroscopy (SERS). AgNPs@MOF with SERS activity was successfully fabricated by synthesizing AgNPs in situ on the surface of MIL-101(Fe), and SDM aptamer and Raman reporter 4-aminophenthiophenol (4-ATP) were selected as specific recognition elements and signal probes, respectively. When SDM was absent, the SDM aptamers were effectively adsorbed on the surface of AgNPs@MOF, thus keeping AgNPs@MOF in a dispersed state, resulting in a weakened SERS signal of 4-ATP. In the presence of SDM, the combination of SDM and aptamer formed a rigid hairpin SDM-aptamer complex, which bound less to AgNPs@MOF. Therefore, fewer aptamers were adsorbed on AgNPs@MOF, which exposed more hot spots, resulting in an enhanced SERS signal of 4-ATP. The aptasensor had good selectivity and sensitivity towards SDM and a good linear relationship between SERS intensity and SDM concentration in the range 6.00–150.00 ng/mL, with the limit of detection as low as 2.73 ng/mL. Further application to honey and chicken samples spiked with SDM resulted in satisfactory recoveries, and the aptasensor showed good stability and reproducibility in real samples. The aptasensor based on AgNPs@MOF was proposed for the first time to detect trace SDM by SERS, which provided a favorable way to develop various sensing platforms for antibiotic detection in food safety. Graphical Abstract