Fabrication of a high sensitivity potentiometric biosensor is described. The present inventors have developed and characterized a novel amplification platform using a gold nanoparticle (GNPs) electrodeposition method. The synthesized GNP sizes were found to be dependent of HAuCl4 concentration, media acid, scan cycles and scan rate. A systematic investigation into the adsorption of different sizes of proteins from aqueous electrolyte solution onto the electrodeposited GNPs surface by the potentiometric method was performed. Results suggest that the size of different proteins affect how they bond to different sizes of GNPs. This GNPs-based biosensor can retain the native-like structure of proteins, and successfully detect proteins at a high sensitivity level. The resulting glucose and immune biosensors also exhibit low detection limit and wide linear range. This improvement to potentiometric devices enables them to serve as highly sensitive detectors for biomolecules and provides a model that can be used to predict protein bonding on nanoparticles.