Self-Assembled Au Nano-Octopus SERS Biosensor for the Interference-Free Detection of Foodborne Pathogens

Escherichia coli O157:H7 represents a major public health threat primarily because of its ability to induce severe gastrointestinal diseases. However, detection in complex biological matrices requires a sensitive, rapid, user-friendly biosensor with high specificity. Herein, we report a hierarchically self-assembled SERS probe, as a central component to the biosensor, Au NanoOctopus (AuNOs)@biosilent Raman reporter 4-mercaptobenzonitrile (4-MBN)@nucleic acid aptamers, designed for the specific capture, ultrasensitive, and interference-free determination of E. coli O157:H7. The Au NanoOctopus enhances the Raman signal of 4-MBN at 2225 cm–1 by a factor of 2.6 × 107, enabling the reduction of the detection limit of SERS biosensors for E. coli O157:H7 in real samples to 1.09 colony-forming unit (CFU) per mL for the first time. The entire process could be completed within 30 min. In the actual measurements of samples such as raspberry juice, this biosensor demonstrated excellent performance: the recovery rate reached 94.33–108.00%, the relative standard deviation was 1.74–7.90%, and the detection results were highly consistent with those obtained using the lytic broth agar plate method. The results of this method were consistent with those derived from the lysogenyl broth agar plate method. These findings suggest that the developed SERS biosensor holds great potential for the quantitative and sensitive screening of E. coli O157:H7 in food safety applications.