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Hydrogen peroxide (H2O2) and glutathione (GSH) have been reported to be associated with a variety of diseases. Therefore, the accurate and rapid determination of H2O2 and GSH was very important. The traditional assay was the colorimetric method, which suffered from the bottleneck of single-mode analysis. In this work, we designed a dual-mode fluorescence and colorimetric sensor for detecting H2O2 and GSH based on bifunctional Fe, Co-CDs, which possessed peroxidase (POD)-mimetic activity and fluorescence property. Concretely, the Fe, Co-CDs catalyzed oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to a blue product (oxTMB) with the help of H2O2, which could be inhibited by GSH. Meanwhile, the fluorescence of Fe, Co-CDs weakened with increasing oxTMB, realizing the fluorescence analysis of H2O2 and GSH. In fluorescence and colorimetric sensors, the detection limit (LOD) of H2O2 could reach as low as 0.54 μM and 0.81 μM, as well as the LOD of GSH was 0.39 and 0.61 μM, respectively. Besides, the smartphone-assisted hydrogel sensor was developed for on-site detection of GSH via color change. This study not only designed a dual-mode sensor for dual-target detection but also provided insights for further exploration of multifunctional nanozymes. [ABSTRACT FROM AUTHOR]

A dual-mode sensor was developed for detecting acetylcholinesterase (AChE) and organophosphorus pesticides (OPs) via bifunctional BSA-CeO2 nanoclusters (NCs) with oxidase-mimetic activity and fluorescence property. The dual-mode sensor has the characteristics of self-calibration and self-verification, meeting the needs of different detection conditions and provide more accurate results. The colorimetric sensor and fluorescence sensor have been successfully used for detecting AChE with limit of detection (LOD) of 0.081 mU/mL and 0.056 mU/mL, respectively, while the LOD for OPs were 0.9 ng/mL and 0.78 ng/mL, respectively. The recovery of AChE was 93.9–107.2% and of OPs was 95.8–105.0% in actual samples. A novel strategy was developed to monitor pesticide residues and detect AChE level, which will motivate future work to explore the potential applications of multifunctional nanozymes. [ABSTRACT FROM AUTHOR]

A novel magnetic nanozyme Fe3O4@MXene-Au nanocomposite, which possessed higher peroxidase-like activity than that of Fe3O4 nanoparticles and Fe3O4@MXene nanocomposites, was developed. The outstanding magnetic properties of the nanozyme endowed it with the ability of simple and rapid separation, achieving great recyclability. Based on Fe3O4@MXene-Au nanocomposites and glucose oxidase (Glu Ox), a highly selective colorimetric biosensor for glucose detection was developed. Fe3O4@MXene-Au nanocomposites can catalyze H2O2 produced from glucose catalyzed by glucose oxidase to ·OH and oxidize colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxidized TMB (oxTMB) with a significant absorbance at 652 nm. The linear range of glucose was 0–1.4 mM under optimal conditions, with a limit of detection (LOD) of 0.11 mM. Glucose in human whole blood was successfully detected with satisfactory recoveries. Furthermore, a facile agarose hydrogel detection platform was designed. With smartphone software, glucose detection can be realized by the agarose hydrogel platform, demonstrating the potential in on-site and visual detection of glucose. [ABSTRACT FROM AUTHOR]