Surface plasmon resonance immunosensor for fast, highly sensitive, and in situ detection of the magnetic nanoparticles-enriched Salmonella enteritidis

• The immunoMNPs were introduced as probes to selectively recognize and separate S. enteritidis.
• The immunoMNPs were introduced as amplification regent to enhance SPR signal.
• In detail, performance of the SPR immunosensor was discussed through various experiments.
• The established SPR immunosensor could be promising in food safety analysis.

A highly sensitive surface plasmon resonance (SPR) immunosensor combining antibody-functionalized Fe3O4 magnetic nanoparticles (immunoMNPs) separation is reported for rapid detection of Salmonella enteritidis (S. enteritidis) based on the sandwich immunoassay. Here, immunoMNPs simultaneously served not only as “vehicles” for rapid delivery of analyte from a sample to the sensor surface, but also as labels increasing the measured refractive index changes associated with the binding of analyte. S. enteritidis can be detected at the concentration as low as 14 cfu/mL with a good linear signal range at 1.4 × 101–1.4 × 109 cfu/mL. Moreover, the use of immunoMNPs gives 4 orders of magnitude improvement in the sensitivity toward S. enteritidis compared with regular SPR immunosensor with direct detection format. The selectivity of proposed SPR approach was examined with Escherichia coli K12 ER2738 and Lactobacillus LJ-3. The recovery of 92.76–113.25% was obtained in eggshell. The developed SPR immunosensor has potential to provide a simple, low-cost and sensitive method for in situ detection of foodborne pathogens.