Patent ID: 8527024
Filing Date: 2013-09-03
Classification: A61B,C12Q

Abstract:
1. An amperometric sensor configured for implantation into the living body of a human or animal to measure the concentration of an analyte in a body fluid, said sensor comprising a counter electrode and a working electrode, said working electrode comprising a sensing layer having a thickness of between at least about 5 μm and 100 μm and which is generally permeable for water and arranged on a support member adjacent to a contact pad, said sensing layer comprising an immobilized enzyme capable of acting catalytically in the presence of the analyte to cause an electrical signal, the sensing layer having an upper surface facing the body fluid and facing away from the support member and a lower surface facing away from the body fluid and facing towards the support member, wherein the immobilized enzyme is distributed in the sensing layer in such a way that the enzyme concentration in the middle between the upper and lower surfaces is at least as high as on the upper surface of the sensing layer, further wherein the sensing layer has an effective diffusion coefficient D eff , which characterizes the diffusion of the analyte in the sensing layer and is about 10-times to about 1000-times lower than the diffusion coefficient D of the analyte in water, the sensor further comprising a diffusion barrier permeable to the analyte covering the sensing layer, the diffusion barrier having a layer with a thickness of between 1 μm and 3 μm.