Electrochemical synthesis of gold nanoparticles in polypyrrole for antibody immobilization

This paper reports a rapid, simple and direct method for the synthesis of gold nanoparticles (AuNPs) in polypyrrole (PPy) film, which provides a biocompatible matrix for the strong adsorption of antibodies. The electrochemical synthesis of AuNPs/PPy composite on gold or carbon electrode occurs within 20 minutes, and does not involve addition of any nanoparticles or reducing agent. This method is compatible to deposit different polymers on miniaturized electrodes selectively. Antibodies were orientedly immobilized on the AuNPs/PPy composite film in the presence of protein A, which provided an adsorption affinity to the Fc fragment of antibodies. Based on an ion-sensitive field-effect transistors (ISFETs) integrated chip, a label-free micro potentiometric HbA1c immunosensor was constructed. The differential voltage response of the sensor changed linearly with the concentration of HbA1c in the range of 0.5-21 mug/ml, with a sensitivity of 0.19 mV mug^-1 ml. The response time was less than 1 min. The sensor has potential use as an inexpensive and portable device for monitoring of diabetes. The developed method can also be used to enhance performances of other immunosensors.