Zwitterion surface modifications for continuous sensors

Devices are provided for measurement of an analyte concentration, e.g., glucose in a host. The device can include a continuous analyte sensor 34 configured to generate a signal associated with a concentration of an analyte, a reference electrode 30, and a sensing membrane 32 located over the working electrode 38. The sensing membrane comprises a diffusion resistance domain configured to control a flux of the analyte therethrough. The diffusion resistance domain comprises one or more zwitterionic compounds and a base polymer comprising both hydrophilic and hydrophobic regions.