Fe3O4@Au nanoparticles enhanced surface plasmon resonance for ultrasensitive immunoassay

Use of metallic or magnetic nanoparticles as amplification labels has been proven a good solution for sensing small molecules or analytes at low concentrations which are difficult to detect directly by conventional surface plasmon resonance (SPR) techniques. Here, an amplification approach combining magnetic Fe3O4@Au nanoparticles (GMNPs) and a magnetic field for a SPR immunoassay is presented. A polydimethylsiloxane (PDMS) microfludic channel was mounted on a conventional SPR device to form the SPR sensor chip. An external magnetic field was applied under the SPR sensor chip for rapid delivery of analyte from a sample solution to the sensor surface. The GMNPs were synthesized by growing Au layers on the Fe3O4 surface. The resulting nanoparticles were characterized with scanning electronic microscopy (SEM), UV–vis spectroscopy and magnetometer. The GMNP amplification effect was evaluated by a sandwich immunoassay to detect human Interleukin 17A (IL-17A). The detection results show the proposed amplification approach provides potential to yield a detection limit of 0.05 ng mL−1.