Development of an ultrasensitive SERS aptasensor for determination of aflatoxin B1 by modifying magnetic beads with UiO-66-NH2 for enhanced signal probe capturing

A versatile Surface-enhanced Raman Spectroscopy (SERS) aptasensor was fabricated for ultrasensitive and stable aflatoxin B1 (AFB1) detection using complementary DNA strands (cDNA) modified Fe3O4@UiO-66-NH2 as capture probe and aptamer modified Au@ 4-MBA@AgNPs as signal probe. The surface of the Fe3O4 beads was functionalized with UiO-66-NH2 to improve the surface area and content of reactive amino groups for stable immobilization of cDNA and capture of more signal probes. Raman tag (4-mercaptobenzoic acid, 4-MBA) embedded Au@AgNPs nanoparticles (Au@4-MBA@AgNPs) was used as signal probes to achieve strong SERS intensity and protect the tag molecules from external interference. When no AFB1 existed, a strong SERS intensity of the signal probe was observed due to the DNA hybridization reaction between the capture and signal probe. While, the addition of AFB1 led to the dissociation of signal probes from the capture probes, leading to a decreased Raman intensity. As a result, a low limit of detection of 1.47 × 10−7 ng/mL and wide linear range from 10−6 to 102 ng/mL were obtained for determination of AFB1 based on the fabricated aptasensor. Moreover, an excellent selectivity and desirable recoveries from 94.3 % to 103.3 % in real maize samples were obtained, demonstrating the fabricated SERS aptasensor is promising in practical applications.