UOX and gout: As the essential biomarker for gout, uric acid (UA) was selected as the model analyte and we used urate oxidase (UOx) as the model enzyme in this study.18,19 UOx catalyzed the oxidation UA to yield H2O220 as a secondary product, which then promoted the covalent immobilization of bovine serum albumin (BSA) onto electrodes through the formation of the disulfide bond between BSA and glutathione (GSH, see Scheme 1 and Scheme S1, ESI†).21