Peroxidase-like activity of bimetal Cu-Zn oxide mesoporous nanospheres for the determination of o-aminophenol

A small library of copper-based metallenes with superior antibacterial activity

We report the preparation of a small library of copper-based metallenes, such as copperene, brassene, bronzene, cupronickelene and AlCuZn trimetallene, via a cryo-pretreatment assisted liquid phase exfoliation method. To the best of our knowledge, these nanosheets may represent a new category of metallenes. Benefiting from mixed-valence copper-induced oxidative stress and cleavage effects of layered structures, the obtained metallenes could efficiently eliminate drug-resistant bacteria even at a concentration as low as 1 μg mL-1. Due to the alloy engineering-induced change in the release rate of metal ions, the CuZn metallene exhibited a much better antibacterial ability than the other metallenes and three clinical antibiotics. We believe this work not only expands the category of emerging 2D metallenes, but also proposes a strategy combining 2D and alloy engineering to improve the antibacterial properties of copper-based materials.

Visible-light-driven photoelectrochemical sensor based on conjugated microporous polymer-grafted graphene for o-aminophenol detection

The pollutant o-aminophenol (o-AP) presents considerable risk to environmental safety, and its detection is therefore critical. Although various optical and electrochemical methods have been proposed for the detection of o-AP, there are a limited number of detection methods based on photoelectrochemical (PEC) sensors. In this study, a sensitive visible-light-driven PEC sensor was developed for o-AP detection in water. A conjugated microporous polymer (CMP)-coated graphene heterostructure (CMP-rGO) was synthesized and used to develop a PEC sensor. Under optimal conditions, the proposed sensor exhibited a high sensitivity of 0.03 μM with a wide linear range of 0.0034-37.6 μM. The PEC sensor also displayed acceptable repeatability and reproducibility, good long-term stability, and excellent recovery (98-102%). In addition, the binding patterns of CMP to o-AP and o-AP analog molecules were analyzed by molecular docking. Therefore, this study provides a new and feasible PEC sensor-based detection scheme for o-AP detection.

Unveiling novel anti-viral mechanisms of ε-poly-l-lysine on tobacco mosaic virus-infected Nicotiana tabacum through microRNA and transcriptome sequencing

MicroRNAs (miRNAs) play important roles in plant defense against various pathogens. ε-poly-l-lysine (ε-PL), a natural anti-microbial peptide produced by microorganisms, effectively suppresses tobacco mosaic virus (TMV) infection. To investigate the anti-viral mechanism of ε-PL, the expression profiles of miRNAs in TMV-infected Nicotiana tabacum after ε-PL treatment were analyzed. The results showed that the expression levels of 328 miRNAs were significantly altered by ε-PL. Degradome sequencing was used to identify their target genes. Integrative analysis of miRNAs target genes and gene-enriched GO/KEGG pathways indicated that ε-PL regulates the expression of miRNAs involved in critical pathways of plant hormone signal transduction, host defense response, and plant pathogen interaction. Subsequently, virus induced gene silencing combined with the short tandem targets mimic technology was used to analyze the function of these miRNAs and their target genes. The results indicated that silencing miR319 and miR164 reduced TMV accumulation in N. benthamiana, indicating the essential roles of these miRNAs and their target genes during ε-PL-mediated anti-viral responses. Collectively, this study reveals that microbial source metabolites can inhibit plant viruses by regulating crucial host miRNAs and further elucidate anti-viral mechanisms of ε-PL.

Spindle-shaped Cu-Ru mesoporous nanospheres with enhanced enzyme-like activity for visual differentiation of toxic o-/m-aminophenol and recognition mechanisms

To effectively differentiate toxic aminophenol isomers, a kind of spindle-shaped Cu-Ru bimetal mesoporous nanozyme (Cu-Ru MPNZ) with high specific surface was developed by one-pot homogeneous reduction method, directed by hexadecyl trimethyl ammonium bromide (CTAB) in this work. By virtue of the distinctive microstructure, Cu-Ru MPNZ expressed superior bi-functional oxidase- and peroxidase-mimic activity to catalyze the oxidation of 3,3',5,5,'-tetramethylbenzidine (TMB) and 2,2'-azinobis (3-ethylbenzothiazoline-6- sulfonic acid) ammonium salt (ABTS) with low Michaelis-Menten constants and quick reaction rates. Especially, toxic aminophenol isomers could exclusively react with the oxydates of TMB or ABTS to express differentiable signals in color. Under the optimal conditions, Cu-Ru MPNZ was successfully applied for visual differentiation of toxic aminophenol isomers in real aqueous, juices and medicinal samples with low detection limits (1.60 × 10-8 mol/L for o-aminophenol and 3.25 × 10-8 mol/L for m-aminophenol) and satisfactory recoveries (96.6-103.5%). The different recognition mechanisms of Cu-Ru MPNZ to toxic o- and m-aminophenol isomers were proposed for the first time as far as we known. This work will provide a potential way to monitor different organic isomer pollution in future.

Convenient colorimetric-fluorescent dual-mode recognition of I- in agricultural products and visual determination of Hg2+ in drinking beverages using Ag-Pt bimetal quantum dot nanozyme

Conveniently and efficiently monitoring I^- and Hg²⁺ in agricultural products or drinking beverages for the protection of human health is currently a great challenge. With this aim, a Ag-Pt bimetal quantum-dot nanozyme boosted by bioactive folic acid (FA@Ag-Pt QDs) was first developed for multichannel monitoring of I^- and Hg²⁺ in this work using a two-step liquid-phase reduction method. Not only did the present FA@Ag-Pt QDs possess superior peroxidase-like activity with Michaelis constant (K_m) and maximal reaction rate (V_max) of 0.01 mM/2.95 × 10^-8 M·s^-1 and 1.15 mM/3.88 × 10^-8 M·s^-1, respectively, trace Hg²⁺ or I^- could exclusively alter their enzyme-mimic performance with obvious color changes from blue to colorless or dark blue. I^- could also strengthen the inherent fluorescence property of FA@Ag-Pt QDs. When applied for visual monitoring of I^- and Hg²⁺ in real beverages or iodine-containing agricultural products, the detection recoveries were 93.9 %-105.3 % and 96.8-104.3 % with low detection limits of 6.56 × 10^-8 mol/L and 4.00 × 10^-10 mol/L (S/N = 3), respectively. The recovery and detection limit for fluorescent detection of I^- were 95.8 %-104.1 % and 1.75 × 10^-8 mol/L (S/N = 3), respectively. The mechanisms driving the improved peroxidase-like activity of FA@Ag-Pt QDs and their selective monitoring of Hg²⁺ and I^- were illustrated in detail. The proposed FA@Ag-Pt QDs will act as an efficient sensor for the practical multichannel monitoring of Hg²⁺ and I^-, with superior catalytic signal amplification.