Biological molecules like proteins, DNA and lipids have strong ionic components in their molecular structures and electrostatic interactions between such biological molecules play important roles in functional binding processes. Immunosensors have been developed based on monitoring pH changes during the metabolic activities. Such potentiometric measurements follow potential changes evolved from ion activity during the binding with no electric current applied. The selectivity for the specific ion detection can be optimized using special membranes on electrode surfaces for the ion differentiation. We've developed another option for selectivity with surface imprinting; the analyte is �molded� on the electrode surface, washed out and the empty cavity of molecular parameters provides the antibody mimicking selective binding.
Antibody-antigen binding or in general protein-protein interactions cannot be diagnosed with metaloxides/electrodes as the electric double layer of less than 1nm allows protein adsorption studies but not interactions on protein surfaces. Organic electronics, electrically conducting polymers, are organic material with 3D composition of ions and electrons, and do have the electric double layer to limit the binding dimensions. We present how polyaniline electrodes can be used for the monitoring protein-protein interactions and also DNA hybridization. Protein studies include determination of the binding conditions for antibody-antigen reactions, and binding studies using lectins and heptapeptides selective for exosporium protein binding. DNA hybridization studies present our efforts on SNP detection, and hybridization with genomic target.