A paper-based conductive immunosensor for the determination ofSalmonella Typhimurium

We report for the first time a highly sensitive and rapid quantitative method for the detection ofSalmonella Typhimurium(S. Typhimurium) using a conductive immunosensor on a paper-based device (PAD).S. Typhimuriummonoclonal antibodies (MA) were first immobilized on a paper-based device and then captured byS. Typhimurium. After an immunoreaction on the device, the polyclonal antibody-colloidal gold conjugate (PA-AuNPs) was dropped to bind withS. Typhimurium. After a complete sandwich reaction, a dark red color appeared on the paper-based device, which can be observed by the naked eye for a rapid screening test. The electrical conductivity of PA-AuNPs between the screen-printed electrodes on the paper-based device was also measured for an accurate quantitative analysis. The electrical conductivity correlated well with the concentration ofS. Typhimurium, which was controlled by the amount ofS. Typhimuriumattached to the polyclonal antibody-colloidal gold conjugate. The device showed a linear correlation for the concentration of theS. Typhimuriumin the range of 10-10(8)CFU mL(-1)in a logarithmic plot, with anR(2)value of 0.9882 and a limit of detection (LOD) as low as 10 CFU mL(-1). This simple, highly sensitive, and rapid method for theS. Typhimuriumdetection was successfully performed within 30 min, and it can be developed into small portable measuring devices in order to facilitate preliminary screening tests.