A single-particle SERS biosensor using aptamer-functionalized hierarchical gold microparticles for highly sensitive and broad-range detection of Staphylococcus aureus

In this study, a sensitive and robust single-particle SERS sensing platform for profiling of Staphylococcus aureus (SA) in complex samples was developed. The hierarchical Au microparticles (HAMs) with intense surfaceenhanced Raman scattering (SERS) enhancement were synthesized. These HAMs were capable of capturing SA by modifying them with specific SA-targeting aptamers. The captured SA was then selectively bound to aptamermodified spherical Au nanoparticles (AuNPs), resulting in a sandwiched structure of HAMs-bacteria-AuNPs. This structure led to enhanced SERS signals, enabling the quantitative detection of SA. We achieved a broad and linear range of SA detection from 1 x 101 to 1 x 106 cfu/mL, with a limit of detection (LOD) of 0.93 cfu/mL. Furthermore, we successfully measured the presence of SA in milk samples, obtaining a recovery rate from 98.2% to 101.1%. These results demonstrate the potential application of the developed method in food safety, infectious diseases, and other health-related safety supervision.