A biosensor based on the biomimetic oxidase Fe3O4@MnO2 for colorimetric determination of uric acid

High plasma urate is closely related to gout, cardiovascular and other diseases. Therefore, monitoring the content of uric acid (UA) in plasma is of great significance for the treatment of gout and the prevention of other related diseases. Herein, a biosensor based on the biomimetic oxidase Fe 3 O 4 nanoparticles (NPs) @MnO 2 nanosheets (Fe 3 O 4 @MnO 2 NS) was constructed for colorimetric determination of UA. MnO 2 NS is an efficient biomimetic oxidase, and we found that the intrinsic oxidase activity of MnO 2 NS doped with Fe 3 O 4 NPs can be significantly enhanced. The chromogenic substrate TMB can be catalyzed by Fe 3 O 4 @MnO 2 NS to generate blue oxidized TMB, and UA can decompose the MnO 2 NS to inhibit the color reaction of TMB selectively, thereby realizing the quantitative detection of UA. In addition, the UA biosensor can perform colorimetric analysis of UA level through three methods: naked eye, smartphone and ultraviolet-visible (UV–vis) spectrophotometer. The linear ranges of UV–vis spectrophotometry and colorimetry with smartphone were 1–70 μM and 200–650 μM, respectively, and the limits of detection (LOD) were 0.27 μM and 21 μM. The analysis results of human plasma samples showed that the method had good selectivity and practicability.