Protein-Directed Metal Oxide Nanoflakes with Tandem Enzyme-Like Characteristics: Colorimetric Glucose Sensing Based on One-Pot Enzyme-Free Cascade Catalysis

It is difficult and significant to realize the aim of one-pot and nonenzyme for traditional colorimetric detection of blood glucose. The synthesis of nanomaterials with 2D morphology is also a challenge for the bovine serum albumin (BSA)-directed method. Here, the BSA-directed synthesis avenue for metal oxide with 2D nanomorphology is developed. MnO2 nanoflakes (NFs) with controllable morphology can be obtained by changing the synthesis conditions. Fortunately, not only is the glucose oxidase (GOx)-like nanozyme (MnO2 NFs) discovered, but MnO2 NFs also show dual enzyme activities (GOx-like activity and peroxidase-like activity) in similar pH range. That is to say, a 'tandem nanozyme (nanomaterial with tandem enzyme-like characteristics) is presented here. Further, the one-pot nonenzymatic strategy is proposed for the colorimetric detection of glucose, where the oxidation of glucose and the colorimetric detection of H2O2 are simultaneously conducted under the catalysis of the single nanozyme (MnO2 NFs). The method shows high sensitivity, low limit of detection, and short detection time, due to the proximity effect and in situ reaction. The as-synthesized 2D tandem nanozyme expands the species of nanozymes, and the proposed strategy breaks traditional colorimetric detection process, accomplishing the purposes of one-pot and nonenzyme in the true sense.