Nanogapped Au(core) @ Au-Ag(shell) structures coupled with Fe3O4 magnetic nanoparticles for the detection of Ochratoxin A

Contamination of mycotoxins has been a general problem of food safety and afflicts people all around the world. Ochratoxin A (OTA), an abundant and representative food-contaminating mycotoxin, has a detrimental effect on our health. Herein, an ultrasensitive surface-enhanced Raman scattering (SERS) aptasensor was fabricated for OTA detection. Au-(core)@ Au-Ag-(shell) nanogapped nanostructures (Au@ Au-Ag NNSs) were coupled with Fe3O4 magnetic nanoparticles (Fe3O4 MNPs) by OTA aptamer and its complementary DNA sequence. The distance between two nanoparticles become far away in presence of the OTA due to the affinity of aptamer. This effect can obviously bring about the change of Raman intensity which can be used for the detection of OTA. Compared with pure metal nanoparticles, Au@ Au-Ag NNSs can effectively enhance the Raman intensity of Raman signal molecule (4-MBA) via the ultrasmall nanogap, which contribute to the sensitivity of the sensor system. Additionally, the utilization of Fe3O4 MNPs offers a green, economical and facile technology to capture targets from solution. The specially modified aptamer and its complementary strand establish a bridge connecting between Au@ Au-Ag NNSs and Fe3O4 MNPs. In this study, OTA concentration with a linear range of 0.01-50 ng mL(-1) and the limit of detection (LOD) was as low as 0.004 ng mL(-1). The proposed SERS aptasensor can combine both of these above type of materials and provide a rapid, sensitive, and low-cost methodology for numerous future applications of point-of-care diagnostics. (C) 2018 Elsevier B.V. All rights reserved.