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Abstract
Fabrication of a novel capacitive immunosensor based on grafted ethylene diamine and
self-assembled gold nanoparticle monolayer on glassy carbon electrode for the detection
of Salmonella spp. is described for the first time. In the present study, the Salmonella
spp. monoclonal antibodies (denoted as McAbs) was immobilized on gold nanoparticles.
Interaction of McAbs and Salmonella spp. was detected directly using the electrochemical
impedance spectroscopy (EIS) technique. The experimental results showed that the concentration
of antigen was measured through the relative change in capacitance in the corresponding
specific binding of Salmonella spp. and McAbs. Under the optimized conditions, the
relative changes in capacitance were proportional to the logarithmic values of Salmonella
spp. concentrations in the range of 1.0 x 10(2) to 1.0 x 10(5) CFU mL(-1) (r = 0.991)
with the detection limit of 1.0 x 10(2) CFU mL(-1). The stability of proposed immunosensor
could be estimated by determining the relative change in capacitance, which remained
almost the same in two months and decreased gradually to 85.3% of initial value after
four months' storage. The used immunosensor could be regenerated repeatedly by immersing
in glycine-HCl buffer solution (pH 2.8). Finally, the proposed immunosensor was successfully
used for the detection of Salmonella spp. in lab-processed commercial pork samples.