Magnetic Nanozyme Based on Loading Nitrogen-Doped Carbon Dots on Mesoporous Fe 3 O 4 Nanoparticles for the Colorimetric Detection of Glucose.

The simple and accurate monitoring of blood glucose level is of great significance for the prevention and control of diabetes. In this work, a magnetic nanozyme was fabricated based on loading nitrogen-doped carbon dots (N-CDs) on mesoporous Fe 3 O 4 nanoparticles for the colorimetric detection of glucose in human serum. Mesoporous Fe 3 O 4 nanoparticles were easily synthesized using a solvothermal method, and N-CDs were then prepared in situ and loaded on the Fe 3 O 4 nanoparticles, leading to a magnetic N-CDs/Fe 3 O 4 nanocomposite. The N-CDs/Fe 3 O 4 nanocomposite exhibited good peroxidase-like activity and could catalyze the oxidation of the colorless enzyme substrate 3,3',5,5'-tetramethylbenzidine (TMB) to blue TMB oxide (ox-TMB) in the presence of hydrogen peroxide (H 2 O 2 ). When the N-CDs/Fe 3 O 4 nanozyme was combined with glucose oxidase (Gox), Gox catalyzed the oxidization of glucose, producing H 2 O 2 and leading to the oxidation of TMB under the catalysis of the N-CDs/Fe 3 O 4 nanozyme. Based on this mechanism, a colorimetric sensor was constructed for the sensitive detection of glucose. The linear range for glucose detection was from 1 to 180 μM, and the limit of detection (LOD) was 0.56 μM. The recovered nanozyme through magnetic separation showed good reusability. The visual detection of glucose was also realized by preparing an integrated agarose hydrogel containing the N-CDs/Fe 3 O 4 nanozyme, glucose oxidase, and TMB. The colorimetric detection platform has an enormous potential for the convenient detection of metabolites.