Nanogap-Assisted SERS/PCR Biosensor Coupled Machine Learning for the Direct Sensing of Staphylococcus aureus in Food.

Staphylococcus aureus ( S. aureus ) is the primary risk factor in food safety. Herein, a nanogap-assisted surface-enhanced Raman scattering/polymerase chain reaction (SERS/PCR) biosensor coupled with a machine-learning tool was developed for the direct and specific sensing of S. aureus in milk. The specific nuc gene ( nuc T) from S. aureus was initially amplified through PCR and subsequently captured via the nanogap effect of I ^- and Mg ²⁺ -mediated bimetallic gold and silver nanoflowers (Au/Ag FL@I ^- -Mg ²⁺ ). These nanogaps generate hotspots for the direct signal amplification of enclosed nuc T. Subsequently, machine-learning tools were used to comparatively analyze the collected SERS signals. The bootstrapping soft shrinkage-partial least-squares method exhibited superior performance (root mean-square error of prediction: 0.437, prediction set correlation coefficient: 0.967). This study demonstrated a novel label-free strategy for specifically detecting S. aureus . The strategy could be advanced to serve as a platform for application to other types of foodborne pathogenic bacteria by engineering a suitable specific primer.