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Sensors 2010, 10(12), 11414-11427; doi:10.3390/s101211414
Article

Direct Detection of the Biological Toxin in Acidic Environment by Electrochemical Impedimetric Immunosensor

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Received: 29 September 2010 / Revised: 27 October 2010 / Accepted: 22 November 2010 / Published: 13 December 2010
(This article belongs to the Special Issue Immunosensors)
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Abstract

This study describes the direct detection of the biological toxin (Ricin) in acidic environment without pH adjustment by hydrophobically modified electrochemical impedance immunosensor (EII). The nano-porous aluminum substrate for EII was hydrophobically modified via self-assembled monolayer (SAM) of APTES. Biosensor for the detection of the Ricin was fabricated by the covalent cross-linking of antibody (Ab) with APTES-SAM. The immunoreactions between the immobilized Ab and the biological toxin in several diagnostic solutions were monitored by the electrochemical impedance spectroscopy (EIS) under the polarization of EII versus reference electrode. EII could detect the presence of the biological toxin in acidic foods in 20 mins without pH adjustment. The negatively charged ions including hydroxides would be adsorbed on the hydrophobic body of APTES-SAMs by the polarization during EIS analysis, and offset the effect of acids on the immunological activity of the immobilized Ab. It suggested that the adsorption of negatively charged ions helped to keep the immunological activities of the immobilized Ab on EII in acidic environment. Proposed mechanism of the localized pH adjustment that makes possible immunoreaction occurrence in low pH sample matrix is briefly discussed.
Keywords: hydrophobic surface modification; immunosensor; direct detection; electrochemical impedance; nano-porous aluminum; antibody immobilization; biological toxin; ricin; acidic foods hydrophobic surface modification; immunosensor; direct detection; electrochemical impedance; nano-porous aluminum; antibody immobilization; biological toxin; ricin; acidic foods
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Chai, C.; Lee, J.; Takhistov, P. Direct Detection of the Biological Toxin in Acidic Environment by Electrochemical Impedimetric Immunosensor. Sensors 2010, 10, 11414-11427.

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