Oxygen-functionalized Fe3O4@o-polypyrrole acting as high-efficiency oxidase mimics and their application in glutathione colorimetric sensing.

The enzyme-like properties of nanozymes may be considerably affected by the structure and surface groups, which thus need to be optimized. Here, through a simple NaOH chemical corrosion method, the chemical structure similar to N-Methylpyrrolidone (NMP), which possessed intrinsic oxidase-like activity, was introduced into polypyrrole (PPy), and then this nanomaterial became oxygen-functionalized PPy (o-PPy) with excellent oxidase-like activity from PPy without this property. Furthermore, after compounding magnetic Fe3O4, the obtained nanocomposites Fe3O4@o-PPy nanoparticles (Fe3O4@o-PPy NPs) showed superiorities in separation during synthesis and real-time control of enzyme catalysis. Studies have found that the enzymatic activity of Fe3O4@o-PPy NPs depended on the amount of functionalized oxygen and the conjugation extent of o-PPy. Fe3O4@o-PPy NPs had efficient oxidase-like activity under a wide range of pH and temperature. Based on the oxidase-like activity of Fe3O4@o-PPy NPs, a colorimetric sensor for glutathione (GSH), which presented rich color changes and satisfactory colorimetric resolution by adding the amaranth, was realized. We believe that the functional modification and structural regulation of PPy can not only realize its wider application but also promote the discovery of novel and efficient nanozymes.

Smartphone-assisted hydrogel platform based on BSA-CeO2 nanoclusters for dual-mode determination of acetylcholinesterase and organophosphorus pesticides.

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.

Magnetic dummy template molecularly imprinted particles functionalized with dendritic nanoclusters for selective enrichment and determination of 4-methylnitrosamino-1-(3-pyridyl)-1-butanone (NNK) in tobacco products.

The compound 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), one of the tobacco specific nitrosamines (TSNAs), is widely recognized as a major carcinogen found in tobacco products, environmental tobacco smoke and wastewater. Thus, a selective enrichment and sensitive detection method for monitoring the risk of NNK exposure is highly desirable. In this study, a magnetic molecularly imprinted polymer (MMIP) functionalized with dendritic nanoclusters was synthesized to selectively recognize NNK via the dummy template imprinting strategy, aiming to avoid residual template leakage and increase the imprinting efficiency. The nanocomposites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, as well as vibrating sample magnetometry (VSM) and nitrogen adsorption/desorption analysis. The resulting MMIPs exhibited high adsorption capacity, fast binding kinetics and good selectivity for trace amounts of NNK. A rapid, low cost and efficient method for detecting NNK in tobacco products was established using magnetic dispersive solid-phase extraction coupled with HPLC-DAD with a good linear range of 0.1-250 µg mL-1. The limit of detection (LOD) and limit of quantification (LOQ) of NNK were 13.5 and 25.0 ng mL-1, respectively. The average recoveries were 87.8-97.3% with RSDs lower than 3%. The results confirmed that the MMIPs could be used as an excellent selective adsorbent for NNK, with potential applications in the pretreatment of tobacco products.