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Here we present the detection of ultralow concentrations of biomolecules in a device made from a polycarbonate membrane containing a network of gold nanowires and using a 'contactless' impedance tomoscopy technique. The sensor comprises a thin dielectric layer with two parallel band electrodes on the one side and a micro-channel containing gold nanowires onto which the adsorption of antibodies occurs. Upon applying a high-frequency ac voltage between the two electrodes, the adsorption process occurring at the surface of the gold nanowires can be followed through contactless impedance measurements. The configuration allows the real-time detection of biomolecules with a bulk concentration in the picomolar range.