High-sensitivity SERS aptasensor for bacterial detection based on covalent organic framework@gold nanoparticle composite

Surface-enhanced Raman spectroscopy (SERS) biosensors have attracted considerable attention for sensitive bacterial detection. In this study, we established a SERS biosensor for highly sensitive detection of Salmonella Typhimurium via the use of porous covalent organic framework-immobilized gold nanoparticles (COF@AuNPs) composites as nanocarriers combined with gold and silver core-shell nanoflowers-enhanced (Au@Ag NFs) substrates to increase the number and intensity of Raman hotspots synergistically. The proposed COF@AuNPs effectively immobilized the AuNPs in the homogeneous pores of the COF, which prevented the aggregation of the AuNPs and provided many binding sites and a stable microenvironment for aptamer loading. This SERS sensor has a linear range of 1 × 10²–1 × 10⁸ CFU/mL and a detection limit of 8.6 CFU/mL. The SERS aptasensor rapidly and accurately detected bacteria in real chicken samples, allowing early diagnosis of S. Typhimurium. This SERS aptasensor provides new strategies for sensitive bacterial detection and may reveal new methods for monitoring other biomolecules.