Immobilization of antibodies on polyaniline films and its application in a piezoelectric immunosensor

Conducting polymers, especially polyaniline (PAni), have been extensively used in biosensor applications. A protocol for covalent immobilization of human IgG on polyaniline using glutaraldehyde as the cross-linker is described in this report and utilized in development of a piezoelectric immunosensor. Here, PAni was used as the substrate for immobilization. The electropolymerization parameters were optimized to get suitable thickness and surface morphology of the PAni for obtaining high density and uniformity of immobilized antibodies on the surface of our films. Possible reaction between PAni thin films and glutaraldehyde was explored using FT-IR characterization in grazing angle mode and XPS. The protocol has been characterized with the help of quartz crystal microbalance analysis. An antibody surface density of 4.86 ng/ mm(2) was obtained. A piezoelectric biosensor developed for detection of IgG with the proposed protocol was capable of differentiating the target analyte concentrations between 500 ng/ mL and 25 mu g/mL with nonspecific binding of similar to 10%.