Method of producing thin enzyme-based sensing layers on planar sensors

A sensor, comprising:

• a substrate comprising a plurality of electrodes;
• an adhesion promoter deposited onto the substrate but not onto the plurality of electrodes;
• a signal transduction enzyme spin-coated onto the substrate with the adhesion promoter and onto the electrodes, wherein the signal transduction enzyme is an oxidase enzyme configured to detect an active compound and is capable of generating an electric current;
• and
• a crosslinker deposited onto the signal transduction enzyme crosslinking the signal transduction enzyme to form a cross-linked enzyme film having a thickness of less than 5 micrometers, wherein the signal transduction enzyme is configured so that a current measured by the plurality of electrodes settles within about 5% of its stable value within one second.