Anti-Interference Near-Infrared SERS Tag-Aptamer Sensor for Rapid Detection of Staphylococcus aureus in Complex Matrices

Rapid detection of bacteria in complex matrices remains challenging due to substantial interference in signal readout. This study developed a novel near-infrared (NIR) surface-enhanced Raman scattering (SERS) sensor featuring exceptional anti-interference capability, achieved by encapsulating SERS tags with a carboxylated polystyrene shell and integrating them with a specific aptamer. The functional PS shell provides reliable physical protection and enables stable covalent bioconjugation, effectively overcoming the limitations of traditional thiol chemistry. Leveraging NIR excitation for minimal background interference, the sensor operates through a target-induced strand displacement mechanism that releases SERS tags upon bacterial binding. After magnetic separation, quantitative analysis is accomplished by directly measuring the SERS signal in the supernatant. Using Staphylococcus aureus as the model bacterium, the method demonstrated outstanding performance in diverse complex matrices including seawater, serum, milk, and traditional Chinese medicine preparations, with a detection limit of 10 CFU/mL and recoveries ranging from 89.96% to 110.6%. This work presents a robust and matrix-adaptive sensing strategy for rapid bacterial detection in complex environments.