Impedance-Probing of Mixed Amphiphile-Antibody Films Transferred onto Silver Electrodes
The impedance spectroscopy was employed to follow the different steps of the immunosensor fabrication and the electronic transduction for the detection of the specific rabbit antigen IgG. A mixed amphiphile (octadecylamine)-antibody Langmuir-Blodgett (LB) film was structured at the air-water interface and transferred onto an octadecyl thiol (ODT) modified silver electrode. Impedance spectroscopy allows one to model the different layers with equivalent electrical circuits. A real probing of the ODT self-assembled monolayer (SAM) was done: electrical defects were found in the ODT SAM and they disappeared after deposition of the LBfilm. It can be suggested that these defects were suppressed by inclusion of octadecylamine (ODA) in the ODT layer. The total impedance of the mixed LBfilm increased in the presence of an increasing concentration of specific antigen. The equivalent circuit shows a decrease of the capacitance of the LBbilayer and an increase of its resistance. Such a structured building-up including biomolecules leads to a reproducible immunosensor, allowing detection of the specific antigen in the range from 10 ng ml –1 to 1200 ng ml –1.
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Document Type: Research Article
Publication date: September 1, 2004
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