Nanogap-based dielectric immunosensing

A novel device for measuring dielectric properties of protein bound to a surface without using a three-electrode system or redox couples is presented. This is achieved by reducing double layer capacitance contributions through decreased electrode gap size (60-100 nm). A proof of concept is demonstrated by immunosensing the glycoprotein laminin, which is clinically relevant to kidney disease at a concentration of 0.5 /spl mu/g/ml. Dissipation factor measurements for different laminin concentrations indicate a detection limit of 10 ng/ml in a 30 microliter droplet. The measurement device described is applicable to a whole range of biological recognition systems including other protein-biomolecule binding interactions and nucleic acid hybridization.