Aptamer-Conjugated Magnetic Nanoparticles Integrated with SERS for Multiplex Salmonella Detection

<i>Salmonella</i> is a rapidly spreading and widespread zoonotic infectious disease that poses a serious threat to the safety of both poultry and human lives. Therefore, the timely detection of <i>Salmonella</i> in foods and animals has become an urgent need for food safety. This work describes the construction of an aptamer-based sensor for <i>Salmonella</i> detection, using Fe₃O₄ magnetic beads and Ag@Au core-shell nanoparticles-embedded 4-mercaptobenzoic acid (4MBA). Leveraging the high affinity between biotin and streptavidin, aptamers were conjugated to Fe₃O₄ magnetic beads. These beads were then combined with Ag@4MBA@Au nanoparticles functionalized with complementary aptamers through hydrogen bonding and π-π stacking interactions, yielding a SERS-based aptamer sensor with optimized Raman signals from 4MBA. When target bacteria are present, aptamer-conjugated magnetic beads exhibit preferential binding to the bacteria, leading to a decrease in the surface-enhanced Raman scattering (SERS) signal. And it was used for the detection of five different serotypes of <i>Salmonella</i>, respectively, and the results showed that the aptamer sensor exhibited a good linear relationship between the concentration range of 10²-10⁸ CFU/mL and LOD is 35.51 CFU/mL. The SERS aptasensor was utilized for the detection of spiked authentic samples with recoveries between 94.0 and 100.4%, which proved the usability of the method and helped to achieve food safety detection.