Glucose oxidase and Au nanocluster co-encapsulated metal-organic frameworks as a sensitive colorimetric sensor for glucose based on a cascade reaction

In this work, glucose oxidase and Au nanoclusters co-encapsulated in zeolitic imidazolate frameworks (GOx & AuNCs@ZIF-8) were obtained by simply mixing Zn2+, dimethylimidazole, glucose oxidase (GOx) and Au nanoclusters (AuNCs) at room temperature. The GOx & AuNCs@ZIF-8 composite can be used as a sensitive colorimetric sensor for glucose based on the following cascade reaction: GOx converts glucose to gluconic acid and generates H2O2, which acts as a substrate for AuNCs oxidizing 3,3 ',5,5 '-tetramethylbenzidine (TMB) to form oxidized TMB (oxTMB) detectable at 652 nm. Owing to the effective cascade reaction and protective effect of the ZIF-8 shell on enzymes, the catalytic activity of GOx & AuNCs@ZIF-8 was enhanced 19.3-fold compared with the free GOx/AuNC solution, and the glucose sensor showed high selectivity and sensitivity. Furthermore, the GOx & AuNCs@ZIF-8 composite showed high long-term storage stability and stability against digesting enzymes and chelating compounds due to the shielding effect of the ZIF-8 scaffold.