Abstract: The invention provides a method and a device for label-free detection of biomolecules or analytes in a sample liquid. The method comprises the steps of allowing an analyte to bind to one of at least two conductive surfaces. An alternating electrical field between at least two conductive surfaces. Amplitude and phase of alternating current, flowing between the at least two conductive surfaces, are compared with amplitude and phase of reference signal. From the difference between both currents it is possible to determine whether an analyte is present at the conductive surface.

Abstract: The invention relates to a device for detecting an analyte comprising a group that can form a covalent bond with the analyte and a detectable moiety, characterized in that the device is a nanoparticle and the detectable moiety is magneto-active, electro-active, or optically active, and to a method for detecting an analyte using a nanoparticle comprising a magneto-active, electro-active or optically active group and a group that can form a covalent bond with the analyte, comprising the steps: a) protecting groups that can form a covalent bond with the nanoparticle, if present on the capture probe; b) bonding the analyte to the optionally protected capture probe to obtain an analyte-capture probe complex of which the analyte contains at least one group that can form a covalent bond with the nanoparticle; c) bringing into contact the analyte-capture probe complex and the nanoparticle to form a covalent bond with each other, d) detecting the analyte which is covalently bonded to the nanoparticle by an amperometri