A colorimetric and surface-enhanced Raman scattering dual-mode "sandwich" immunosensor for ultrasensitive detection of Salmonella.

Herein, a dual-mode approach combining colorimetry and surface-enhanced Raman scattering (SERS) were developed for Salmonella detection. Immunomagnetic beads were used to separate and concentrate the Salmonella. And the GOx@ZIF-90@PDA@pAbs were used as signal probe to catalyze glucose to form HO. In the presence of HO, tyramine (TYR) aggregation was brought on by HRP-catalyzed phenol polymerization, which led to the aggregation of AuNPs through the strong electrostatic interactions between TYR and AuNPs. Based on the enzymatic cascade catalyzed signal amplification induced AuNPs aggregation, the dual-mode method exhibited wide linear range (10-10 CFU/mL) and high sensitivity. The limit of detection (LOD) of colorimetric mode was 34 CFU/mL, while the LOD was 5 CFU/mL in SERS mode, which was 6.8-fold lower than that of colorimetric mode. Furthermore, the two modes demonstrated high specificity and applicability, which might be a promising method for rapid and sensitive detection of Salmonella to ensure food safety.