Ultrasensitive Detection of Chloramphenicol in Milk Using a “Y-Shaped” SERS Biosensor Based on Magnetic Plasmonic Nanostructures and EXPAR Technology

Chloramphenicol (CAP), as a broad-spectrum antibiotic, is genotoxic to humans. In this paper, a "Y-shaped" SERS biosensor based on magnetic plasmonic superstructures Fe3O4@SiO2@Ag flowers and the highly efficient isothermal amplification strategy of exponential amplification reaction (EXPAR) technology was proposed for ultrasensitive detection of CAP in milk. This was achieved by forming a stable "Y-shaped" structure on the abundant sharp tips of Fe3O4@SiO2@Ag flowers through specific three-part assembly (Probe 1 connected to the magnetic substrate, Signal Probe 2 Au@4-NTP, and the EXPAR amplification product Amplicon). When the CAP was present, the Amplicon obtained from EXPAR amplification could form a "Y-shaped" structure with the magnetic material and the signal probe. Benefiting from the abundant branching, extensive surface area, and rough surface of the magnetic Fe3O4@SiO2@Ag flower, it offers a multitude of "hot spots" for plasmonic coupling in the electromagnetic field gap region and significantly reduces the nanogap between the signal probe and the silver nanoflowers by constructing a "Y"-shaped structure, thereby maximizing the amplification of the Raman signal. Enabling the detection range of CAP to be between 10–6 and 10–13 M with a detection limit of 17.9 fM. This strategy provided an avenue for trace detection of CAP in food.