Human serum albumin templated MnO nanosheets are oxidase mimics for colorimetric determination of hydrogen peroxide and for enzymatic determination of glucose.

This paper reports on a colorimetric assay for HO and glucose. It is based on the use of human serum albumin-templated MnO nanosheets that possess oxidase-like activity. They are capable of oxidizing 3,3',5,5'-tetramethylbenzidine (TMB) with oxygen to give a blue product (oxTMB) with an absorbance maximum at 652 nm. When HO is introduced, the MnO nanosheets are reduced to Mn(II) ions, and this inhibits the formation of oxTMB. Based on these findings, a colorimetric assay was established for HO that has a 0.56 μM detection limit. If glucose is oxidized by glucose oxidase under formation of HO, the nanosheets can be used to quantify HO and thereby to sense glucose. Response is linear in the 0.5 μM to 50 μM glucose concentration range, and the detection limit is 0.32 μM. The method was applied to the determination of glucose in spiked serum samples and gave satisficatory results. Graphical abstract Human serum albumin (HSA) is used as a template for the synthesis of MnO nanosheet. These possess oxidase mimicking activity. HO can reduce the nanosheets. The effect is exploited in colorimetric assays for HO and glucose using tetramethylbenzidine (TMB) as a chromogenic substrate.