Electrical classification of the concentration of bioconjugated metal colloids after surface adsorption and silver enhancement

A scheme for an electrical classification of the solution concentration of bioconjugated colloidal gold particles is presented. It is based on the imm obilization of the particles in the gap of microstructured electrodes, foll owed by a metal enhancement step and electrical measurements. The surface d ensity of particles depends on the solution concentrations, and the metal e nhancement classifies this density by yielding conductive surfaces only for densities above a threshold. Size enhancement ratios of up to 10 were obse rved for 30 nm particles and could be controlled by the incubation time.