High-efficiency enzyme-free catalyzed hairpin assembly-mediated homogeneous SERS and naked-eyes dual-mode assay for ultrasensitive and portable detection of mycotoxin

We developed an aptamer recognition-trigged enzyme-free catalyzed hairpin assembly (CHA) assisted signal amplification homogeneous naked-eyes and surface-enhanced Raman scattering (SERS) dual-mode sensor for highly sensitive and portable detection of Aflatoxin B1 (AFB1) in food samples. The recognition of AFB1 by aptamer induced the generation of HP1-AFB1 complexes, which hybridized with Ag+-labeled hairpin DNA (HP2) and released Ag+, subsequently initiating the enzyme-free CHA reaction by a designed helper DNA (HP3) to form double-stranded DNA (HP2-HP3) and accompanied by the release of HP1-AFB1 complexes. The released HP1-AFB1 complexes were recognized by HP2 and HP3 again to trigger cascade recycling amplification and resulted in the generation of a larger number of free Ag+ and dsDNA. Then, methylene blue as Raman tag to intercalate into dsDNA and generating strong SERS signal with the assistance of Fe3O4@Au. Meanwhile, the free Ag+ induced the AuNPs aggregation and resulted in naked-eye distinguishable color transitions from red to black blue. Benefitting from the efficiently enzyme-free CHA assisted signal amplification and portably dual-mode detection system, this work successfully proposed a novel homogeneous biosensing strategy for highly sensitive and portable detection of AFB1. The SERS intensity and visualization signals were linearly correlated with the concentration of AFB1 ranging from 0.0156 to 31.2 ng mL-1 and 0.61-39 ng mL-1, and the limit of detections were 1.6 pg mL-1 and 152 pg mL-1, respectively. This strategy was successfully applied to real samples and provided an alternative approach for the highly sensitive detection of mycotoxins.