Lateral flow strip biosensor based on streptavidin-coated gold nanoparticles with recombinase polymerase amplification for the quantitative point-of-care testing of Salmonella

Salmonella is a widespread and highly infectious biological contaminant that causes zoonotic diseases. Most detection methods are qualitative, while quantitative methods are time-consuming and rely on large analytical instruments. Therefore, the development of a rapid, simple, and quantitative assay is important for the prevention and control of infection at the early stages of an outbreak. To address this requirement, we developed a lateral flow (LF) strip biosensor based on streptavidin-coated gold nanoparticles (StreptAv–AuNPs) combined with recombinase polymerase amplification (RPA) for the quantitative point-of-care testing of Salmonella enterica serotype Enteritidis (S. Enteritidis). StreptAv-AuNPs were simple to synthesise and bound firmly to DNA with end-modified biotin. RPA could greatly reduce detection time. A smartphone was used to collect images of the LF strip and input them into a laptop for quantitative analysis. The entire process was completed in less than 40 min and did not require large laboratory equipment or analytical instruments. A limit of detection of 5.5 × 10−13 M and 91.4 CFU/mL was achieved for synthetic S. Enteritidis DNA and cultured S. Enteritidis samples, respectively. In the reproducibility assay, RSD values of 5.88%, 5.13%, and 4.45% were achieved for the three different concentrations of samples. This method has the advantages of low cost, high precision and rapid quantification, it is also suitable for the detection of various DNA-containing analytes.