An investigation on the multiple roles of CeO2 nanoparticle in electrochemical sensing: Biomimetic activity and electron acceptor

Nanomaterials with enzyme-like activity (nanozymes) are known to be suitable alternatives for natural enzymes tolerating unfavorable pH and temperature conditions. The enzyme-like activity of CeO2 nanoparti-cles was already reported and used in electrochemical sensing, where the peroxidase or oxidase-like activities of CeO2 NPs are mainly used. This work aims to justify the role/s that CeO2 may play in electrochemical sens -ing as a nanozyme and acts as a mediator. To this end, a reduced graphene oxide-CeO2 was prepared and used in two electrochemical sensing configurations. In first configuration, H2O2 reduction was catalyzed at the glassy carbon electrode modified with the rGO-CeO2 nanocomposite (rGO-CeO2 NC). The reduction current obtained upon the presence of H2O2 was attributed to a mediator role having a linear range of 100.0-800.0 mu mol L-1 with a limit of detection (LOD) and limit of quantification (LOQ) of 15.9 mu mol L-1 and 52.9 mu mol L-1, respectively. In another configuration, glucose oxidase was used as a model enzyme with the rGO-CeO2 NC. The oxidation signal obtained upon adding glucose was attributed to the electron-accepting role of the CeO2 NPs. The analytical figures of merit obtained for both configurations indicated their high sen-sitivity, selectivity, and reproducibility. The linear detection range for the nanozyme-enzyme cascade system was 100.0-800.0 mu mol L-1 with a LOD and LOQ of 18.7 mu mol L-1 and 62.3 mu mol L-1, respectively. Moreover, the flow injection analysis was enabled due to the short response time in analysis with the prepared sensor. The possibility for applying the developed nanozyme in nanozyme-enzyme cascade system in clinical and food analysis for determination of glucose was verified by studying the interference of various compounds similar to glucose in structure and typical drugs taken by diabetic patients.

Automated summary

CeO2 nanoparticles with enzyme-like activity can serve as alternatives to natural enzymes in electrochemical sensing, exhibiting favorable mediator and catalytic roles in H2O2 reduction reactions.