Outer layer for enzyme sensors

A planar enzyme sensor for measuring the concentration of an analyte in a solution, the sensor comprising a substrate of an electrically insulating material supporting an electrode layer of an electrically conductive material, said substrate and electrode layer having a plurality of layers disposed thereon, said plurality of layers at least including:

• a. an enzyme layer comprising at least one first enzyme;
• and
• b. a microporous outer layer covering the enzyme layer, said outer layer comprising (i) a continuous phase of a water-resistant polymer and (ii) a protein embedded in said continuous phase,
• wherein the water-resistant polymer forming said continuous phase of said outer layer is selected from the group consisting of polyvinylacetate and copolymers of ethylacrylate and methylmethacrylate, and
• wherein the microporous outer layer further comprises polymer particles embedded in said continuous phase.