Nafiseh Abedi - M.Sc. Molecular Biotechnology, Faculty of Chemistry and Chemical Engineering, Malek Ashtar University of Technology, Iran.
Mehdi zeinoddini - PhD, Biochemistery, Associate Professor, Faculty of Chemistry and Chemical Engineering, Malek Ashtar University of Technology, Iran.
mohammad shoushtari - PhD, Virology, Department of Virology, Pasteur Institute of Iran, Tehran, Iran

Salmonella typhimurium is a type of pathogenic bacteria that is crucial in medicine and the food industry, as it can cause food poisoning, such as typhoid or typhoid fever. However, diagnosing this bacterium can be challenging since its symptoms, including fever, diarrhea, and dizziness, are common in many diseases. Hence, a specific and effective diagnostic method is needed to identify S. typhimurium accurately. The aim of this study is develop a sensor immunoassay using aptamer-based lateral flow assay (LFA) to detect S. typhimurium. For this, anti- Salmonella aptamer conjugated with gold nanoparticles (GNPs), firstly for design of a nanobioprobe and as a signal probe, and used in LFA. The test involved a competitive format between the bacteria immobilized on the membrane and the bacteria present in the tested sample. In the following, the optimization of various factors affecting the aptamer LFA including the concentration of bacteria in stabilized form and into the sample, and the concentration of nanobioprop, was performed using the Taguchi test design method. The data showed that the optimal conditions for the LFA reaction was ۱۰۸ cfu/mL of stabilized bacteria and ۱.۵ μg/μL of nanobioprop concentration and under these conditions, the visual detection limit of S. typhimurium was estimated and calculated to be ۱۰۵ cfu/mL. The reaction results are obtained within ۲۰ minutes, and there were no significant cross-reactions with other food pathogens. In conclusion, the optimized aptamer-LFA diagnostic method provides a reliable, simple, and accurate tool for detecting S. typhimurium, and it can be used as a portable diagnostic kit for this bacterium in future investigation.

Aptamer, Lateral flow assay, Salmonella typhimurium, Taguchi test design