AuNanostar@4-MBA@Au Core–Shell Nanostructure Coupled with Exonuclease III-Assisted Cycling Amplification for Ultrasensitive SERS Detection of Ochratoxin A

The "turn-on" mode surface-enhanced Raman scattering (SERS) aptasensor for ultrasensitive ochratoxin A (OTA) detection was developed based on the SERS "hot spots" of AuNanostar@4-MBA@Au core-shell nanostructures (AuNS@4-MBA@Au) and exonuclease III (Exo III)-assisted target cycle amplification strategy. Compared with conventional gold nanoparticles, AuNS@4-MBA@Au provides a much higher SERS enhancement factor because AuNS exhibits a larger surface roughness and the lightning rod effect, as well as an excellent electromagnetic field between the AuNS core and the Au shell, which contribute to the superstrong SERS signal. Meanwhile, Exo III-assisted target cycle amplification can be used as an effective method for the further amplified detection of OTA. Additionally, the utilization of streptavidin magnesphere paramagnetic particles offers a green, economical, and facile technology for the accumulation and separation of the signal probe AuNS@4-MBA@Au from solution. All these factors lead to a significant enhancement of detectable signals and superhigh sensitivity. As a result, the limit of detection as low as 0.25 fg mL^-1 could be achieved, which was lower than that in the other reported literatures on SERS methods for OTA detection as we know. The developed SERS aptasensor also provides a promising tool for foodstuff detection.