Highly sensitive electrochemical immunosensor for IgG detection based on optimized rigid biocomposites

In this work we present the construction of immunosensors based on graphite-epoxy which incorporate RIgG to the composite matrix. In order to improve the electrochemical properties of the immunocomposite electrodes, characterization and optimization was carried out in terms of electrochemical impedance spectroscopy and cyclic voltammetry. Consequently, taking into the account the properties required by a sensitive electrode such as high electron-transfer rate, high signal-to-noise ratio and suitable sensitivity; the optimal proportion of the transducer material (graphite-epoxy ratio) was chosen using constant amount of RIgG. The optimum composition range values, which provide these requirements, were from 16% to 17% of graphite loading. Then, the analytical properties of these immunosensors were evaluated measuring RIgG by using a competitive assay and using alkaline phosphatase-labeled antibody. Amperometric measurements were performed using hydrogen peroxide as substrate. Moreover, it has been the first time that it has been performed an optimization of the antigen-antibody ratio used in the assay, being this reduced significantly.