Sensitive immunodetection through impedance measurements onto gold functionalized electrodes

This article deals with a direct electrochemical method of detecting antige ns using new methods of functionalization of gold electrodes. Based on the reacting ability of gold with sulfhydryl groups, three protocols for the fi xation of antibodies have been explored. They are based on either the self- assembling properties of functional thiols bearing long alkyl chains or the possibility of a direct coupling of antibody moieties. Coverage rates as h igh as 97% can be reached. The analysis of the electrochemical impedance be havior of such layers can lead to a sensitive method for the direct detecti on of the antibody/antigen interaction. The addition of a redox couple in t he tested solution, acting as an amplifier, allowed detection limits for th e antigens as low as a few picograms/milliliter to be reached.