Journal
ANALYTICA CHIMICA ACTA
Volume 624, Issue 2, Pages 301-307Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.aca.2008.06.043
Keywords
faradic electrochemical impedance spectroscopy; immunosensors; Salmonella typhimurium; electropolymerized polytyramine films; on-site detection of pathogens
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Funding
- Hellenic Ministry of Development
- PAVET-NE/Nr. 04BEN35
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The development of a faradic impedimetric immurrosensor based on electropolymerized polytyramine (Ptyr) films for the detection of S. typhimurium in milk is described for the first time. Polyclonal anti-Salmonella was cross-linked, in the presence of glutaraldehyde vapors, on Ptyr-modified gold electrodes. The dielectric behaviour of Ptyr films was evaluated with capacitance measurements, while their stability in neutral aqueous solutions was examined with impedimetric measurements. The effect of the concentration of tyramine in the forming solution on both the sensitivity and the dynamic range of the resulted immunosensors was also investigated. The alteration of the interfacial features of the electrodes due to different modification or recognition steps, was measured by faradic electrochemical impedance spectroscopy in the presence of a hexacyanoferrate(II)/(III) redox couple. At samples containing a low initial concentration of 10 cfu mL(-1) S. typhimurium, that actually defines the LOD of the immunosensors, signal changes of 33% and 88% were achieved after 3 and 10h incubation, respectively. To achieve the working simplicity expected by a biosensor, immunoreaction was performed directly in cultures. This resulted in the elimination of various centrifugation and washing steps, which are used for the isolation of bacteria cells from the culture, thus making the proposed immunosensors promising candidates for on-site applications. Finally, the proposed immunosensors were successfully used for the detection of S. typhimurium in experimentally inoculated milk samples. (c) 2008 Published by Elsevier B.V.
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