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

Abstract

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.

“Non‐Naked” Gold with Glucose Oxidase‐Like Activity: A Nanozyme for Tandem Catalysis

“…By contrast, we had successfully synthetized a unique nanozyme (Au@BSA NPs), which had the similar pH range of dual enzyme activities. So, as‐synthesized Au@BSA NPs could be called as “tandem nanozyme,” which had two catalytic activities (peroxidase‐like and the GOx‐like activities) and could simultaneously catalyze the cascade reactions …”

“…With the development of nanotechnology, nanozymes are widely used as substitutes of natural enzymes . The reported enzyme‐like activities include the peroxidase‐like activity, superoxide dismutase‐like activity, catalase‐like activity, and so on.…”

“…The reported enzyme‐like activities include the peroxidase‐like activity, superoxide dismutase‐like activity, catalase‐like activity, and so on. However, there are relatively few reports about glucose oxidase (GOx)‐like activity . In 2004, Rossi and co‐workers first discovered that the “naked” gold nanoparticles (Au NPs) synthesized without protectors or stabilizers had GOx‐like activity .…”

Development of Nanozymes for Food Quality and Safety Detection: Principles and Recent Applications

“…Except for POD‐ or OXD‐like nanozymes, a few enzyme mimics can perform detection applications by using the analytes as catalytic substrate to produce detectable ox‐substrates (Figure A, recognition 1). For instance, Au NPs or MnO 2 nanosheets (NSs) with GOX‐like activities have been exploited for detecting glucose (Han, Zhang, Chen, & Li, ; Huang, Zhao et al., ), and Co 3 O 4 /reduced graphene oxide nanocomposites (Co 3 O 4 /rGO) can act as an effective artificial phosphotriesterase for detection of paraoxon (Wang, Wang, Yang, Su, & Yang, ).…”

“…However, this principle of detection has limit because the catalytic pH condition of POD‐like mimics is sometime incompatible with that of GOX. Thereby, researchers facilitated one‐pot detection systems for more simple and rapid glucose detection using nanomaterials with dual POD‐ and GOX‐like activities, such as Au NPs or MnO 2 NSs (Han et al., ; Huang, Zhao et al., ). In addition to glucose, cholesterol is also an important indicator of clinical diagnosis, which is often measured in food and clinical samples.…”