Dual mimic enzyme properties of Fe nanoparticles embedded in two-dimensional carbon nanosheets for colorimetric detection of biomolecules

The development of novel nanozymes is of great importance for the efficient analysis of biomolecules such as H₂O₂, glucose, and antioxidants in the diagnosis of some diseases. Herein, novel nanozymes based on Fe nanoparticles (NPs) encapsulated in 2D carbon nanosheets (denoted as Fe@CNs) were constructed and employed in the field of biosensing. Notably, Fe@CNs have intrinsic dual mimic enzyme properties. The colorless colorimetric substrate 3,3′,5,5′-tetramethylbenzidine (TMB) can be oxidized by Fe@CNs as oxidase- and peroxidase-like nanozymes, respectively. The generation of the oxidation state TMB (oxTMB) resulted from the presence of reactive oxygen species (ROS) which were produced by the catalytic decomposition of the dissolved oxygen or H₂O₂. Thus, a simple colorimetric biosensor was proposed to detect glutathione (GSH), H₂O₂, and glucose. In addition, the Fe@CN-based nanozymes also have excellent reusability in enzymatic catalysis. After separating from the sensing systems, Fe@CNs can be reused in other catalytic processes. This colorimetric method could be used as a universal sensing platform for the detection of antioxidants and H₂O₂-related bioanalysis. This work broadens the application of novel nanozymes in biosensing.