Ceria nanoparticle compositions for use as electrode materials for in vivo electrochemical analyte sensors (e.g., glucose sensors) are provided, for example to form a cathode or a reference electrode. The ceria nanoparticle compositions may be combined with a conductive material (e.g., mixed with) to form the cathode or the reference electrode, or the ceria nanoparticle compositions may be deposited over conductive material to form the cathode or the reference electrode. Electrochemical in vivo sensors for monitoring the concentration of an analyte having a reference electrode and/or a cathode that includes a ceria nanoparticle composition, and methods for monitoring an analyte concentration using the electrochemical sensors are also described. Methods of making in vivo electrochemical analyte sensors having a reference electrode and/or a cathode that includes a ceria nanoparticle composition are also provided.
