Nanozyme-based sensitive ratiometric fluorescence detection platform for glucose

Development and application of carbon-based nanozymes are attracting wide interest in recent years. Abnormal glucose level can be threat to human health. Sensitive and accurate sensing methods for glucose are still of great urgency. In this work, we constructed a sensitive nanozyme-based ratiometric fluorescence sensing platform for glucose. The sensing system composed of copper-doped carbon-based nanozyme (CuAA) with superb peroxidase-like activity and Mg/N doped carbon quantum dots (Mg–N-CQDs) with distinguished fluorescence property. Efficient tandem catalysis of glucose oxidase (Glu Ox) and CuAA, and inner-filter effect (IFE) between 2, 3-diaminophenazine (DAP) and Mg–N-CQDs played crucial roles in this sensing system. The oxidization of glucose was catalyzed by Glu Ox firstly to produce H₂O₂. In the presence of H₂O₂, fluorescent DAP was formed from non-fluorescent substrate o-phenylenediamine (OPD) with assistance of CuAA, resulting in generation of emission at 558 nm. Meanwhile, the emission at 444 nm from Mg–N-CQDs was quenched efficiently by DAP through IFE. The ratiometric fluorescence signal I₅₅₈/I₄₄₄ increased linearly with glucose concentration in the scope of 2–400 μmol L⁻¹, the limit of detection (LOD) was 1.56 μmol L⁻¹. It was also practicable to apply the method to the determination of glucose in human serum, satisfactory recoveries and RSDs were acquired.