Nanospheres with colorimetric and SERS properties for Lateral Flow Assay of Salmonella

• The AuNP@PDA@Ag MBA has colorimetric and SERS properties. • PDA-wrapped AuNPs improve the colorimetric signal strength. • RPA amplifies the target DNA to further amplify the signal and improve sensitivity. Salmonella enteritidis is a common foodborne pathogen in nature, which poses a serious threat to human and animal health. Rapid and accurate detection of salmonella enteritidis is an effective way to control its spread, but the traditional colorimetric method is difficult to quantify accurately. We report a simple in situ growth reduction method for the preparation of nanospheres AuNP@PDA@Ag MBA with unique colorimetric and Raman properties, which can be visually qualitative while Raman quantitative detection. With AuNPs as the core, the nanosphere is coated with polydopamine to provide a stronger colorimetric signal and reduce the visual limit of detection (LOD). The modification of 4-mercaptobenzoic acid molecules resulted in a strong surface enhanced Raman scattering (SERS) signal. After the target DNA was amplified by recombinant polymerase amplification, the colorimetric and SERS signal were further amplified. The detection process was carried out on the lateral flow strip, and the black strip was formed to achieve qualitative and quantitative analysis. In the concentration range of 3 × 10 1 to 3 × 10 5 CFU/mL, the visual LOD was 3 × 10 1 CFU/mL. The SERS intensity was detected, and there was a good linear relationship between the signal intensity and the logarithmic value of DNA concentration, and the LOD of Raman mode was 1.51 CFU/mL.