Diffusion resistance layer for analyte sensors

A device for measurement of an analyte concentration, the device comprising:

• a transcutaneous sensor configured to generate a signal associated with the analyte concentration;
• and
• a sensing membrane located over the transcutaneous sensor, the sensing membrane comprising a diffusion-resistance layer, wherein the diffusion-resistance layer comprises a blend comprising a polyurethane-containing block copolymer and a polyvinylpyrrolidone, the polyurethane-containing block copolymer comprising a polycarbonate-urethane that comprises 5% to 50% by weight hard segment and 5% to 50% by weight soft segment wherein the hard segment having a lowest glass transition temperature as measured using ASTM D3418 of greater than −50° C., wherein the block copolymer comprises at least one internal zwitterionic group in a backbone, wherein the block copolymer comprises less than 1 wt. % polysiloxane.