A Co-based MOF as nanozyme with enhanced oxidase-like activity for highly sensitive and selective colorimetric differentiation of aminophenol isomers

2-Methylbenzimidazole-copper nanozyme with high laccase activity for colorimetric differentiation and detection of aminophenol isomers

Laccase is well-known for its eco-friendly applications in environmental remediation and biotechnology, but its high cost and low stability have limited its practical use. Therefore, there is an urgent need to develop efficient laccase mimetics. In this study, a novel laccase-mimicking nanozyme (MBI-Cu) was successfully synthesized using 2-methylbenzimidazole (MBI) coordinated with Cu2+ by mimicking the copper active site and electron transfer pathway of natural laccase. MBI-Cu nanozyme exhibited excellent catalytic activity and higher stability than laccase, and was utilized to oxidize a series of phenolic compounds. Environmental pollutant aminophenol isomers were found to display different color in solution when catalytically oxidized by MBI-Cu, which provided a simple and feasible method to identify them by the naked eye. Based on the distinct absorption spectra of the oxidized aminophenol isomers, a colorimetric method for quantitatively detecting o-AP, m-AP, and p-AP was established, with detection limits of 0.06 μM, 0.27 μM, and 0.18 μM, respectively. Furthermore, by integrating MBI-Cu-based cotton pad colorimetric strips with smartphone and utilizing color recognition software to identify and analyze the RGB values of the images, a portable colorimetric sensing platform was designed for rapid detection of aminophenol isomers without the need for any analytical instrument. This work provides an effective reference for the design of laccase nanozymes and holds significant potential for applications in the field of environmental pollutant monitoring.

Recent advances in MOF-based nanozymes: Synthesis, activities, and bioapplications

Nanozymes have garnered considerable research interest for their unique capacity to bridge nanotechnology and biology. Current studies predominantly concentrate on exploring nanozymes with diverse catalytic activities and their potential applications across various disciplines. Among them, nanoscale metal-organic frameworks (MOFs) are promising nanomaterials for constructing nanozymes. In this review, we firstly introduce the general construction strategies for MOF-based nanozymes. In addition, we also classify the MOF-based nanozymes in detail based on their catalytic performance. Thirdly, the recent research progress of MOF-based nanozymes in the field of biosensing, cancer therapy, antibacterial infection, and antioxidation are also comprehensively reviewed. Finally, we discuss the current challenges and future perspectives of MOF-based nanozymes, with the aim of assisting in their construction and maximizing their potential in bioapplications. It is hoped that we could provide scientists in materials science and biomedical research with valuable and comprehensive information, fostering advancements in interdisciplinary fields.

MoO3/MIL-125-NH2 with boosted peroxidase-like activity for electrochemical staphylococcus aureus sensing via specific recognition of bacteriophages

Herein, novel nanozyme mimics MoO3/MIL-125-NH2 were reported and conjugated with bacteriophages as a new electrochemical probe for high sensitivity and specific electrochemical detection of staphylococcus aureus. The excellent peroxidase-like activity of MoO3/MIL-125-NH2 composites was attributed to the integration of MIL-125-NH2 with MoO3, which can boost the generation of superoxide radicals (O• 2-) and thus promote the oxidation of TMB in the presence of H2O2. In this work, two bacteriophages named SapYZU04 and SapYZU10 were isolated from sewage samples by using staphylococcus aureus YZUsa12 as the host. In comparison, MoO3/MIL-125-NH2@SapYZU04 was selected as a recognition agent. The DPV current declined linearly with staphylococcus aureus YZUsa12 concentration in the range of 101-108 CFU mL-1, with a low detection limit of 16 CFU mL-1 (S/N = 3). 20 strains including 13 host strains and 7 non-host strains were used to evaluate the selectivity of the proposed sensor. Regardless of the differences in the degrees of lytic performance for phage SapYZU04, all selected host strains can be screened with merely the same DPV current. Host spectrum-oriented bacteriophage sensing is of great importance for the practical application of bacteriophage-based biosensors in the future.

Advancing stroke therapy: the potential of MOF-based nanozymes in biomedical applications

In this study, we explored the growing use of metal-organic framework (MOF)-based Nanozymes in biomedical research, with a specific emphasis on their applications in stroke therapy. We have discussed the complex nature of stroke pathophysiology, highlighting the crucial role of reactive oxygen species (ROS), and acknowledging the limitations of natural enzymes in addressing these challenges. We have also discussed the role of nanozymes, particularly those based on MOFs, their structural similarities to natural enzymes, and their potential to improve reactivity in various biomedical applications. The categorization of MOF nanozymes based on enzyme-mimicking activities is discussed, and their applications in stroke therapy are explored. We have reported the potential of MOF in treating stroke by regulating ROS levels, alleviation inflammation, and reducing neuron apoptosis. Additionally, we have addressed the challenges in developing efficient antioxidant nanozyme systems for stroke treatment. The review concludes with the promise of addressing these challenges and highlights the promising future of MOF nanozymes in diverse medical applications, particularly in the field of stroke treatment.

Multisignals Sensing Platform for Highly Sensitive, Accurate, and Rapid Detection of p-Aminophenol Based on Adsorption and Oxidation Effects Induced by Defective NH2-Ag-nMOFs

Labile toxic pollutants detection remains a challenge due to the problem that a single method is prone to producing false-negative/-positive signals. The construction of a multisignal sensing platform with the advantages of different strategies is an effective way to solve this problem. Herein, a novel resonant light scattering (RLS), fluorescent and rapid visual multisignals sensing strategy for p-aminophenol (p-AP) detection was designed based on the adsorption and oxidation effects of defective amino-functionalized Ag-based nano metal-organic frameworks (NH2-Ag-nMOFs). In this reaction process, NH2-Ag-nMOFs with incomplete coordination oxidize H2O2 to produce singlet oxygen (1O2) which rapidly oxidizes p-AP, leading to the reduction of Ag+ to Ag0, thereby disrupting the structure of NH2-Ag-nMOFs and resulting in fluorescence quenching of NH2-Ag-nMOFs. Synchronously, owing to Ag0 aggregation and p-AP oxidation, the color of the system changed from colorless to purplish-red and pale brown within 20 s. The assay has realized the rapid naked-eye detection of 5 μM p-AP rapidly. Additionally, thanks to the intermolecular hydrogen bonding, NH2-Ag-nMOFs-p-AP aggregates formed, which enhanced the RLS signal. With the RLS signal, the designed multisignals sensing platform can analyze p-AP at a concentration as low as 11 nM and yield a wider dynamic response range than any single signal strategy reported before, which can quickly meet the measurement requirement of different actual samples. Overall, the proposed strategy without assembling various signal indicators presented an accurate, rapid, cost-effective, and sensitive multisignals sensing platform for p-AP analysis and has great prospects in labile toxic pollutants monitoring.

Co-based Nanozymatic Profiling: Advances Spanning Chemistry, Biomedical, and Environmental Sciences

Nanozymes, next-generation enzyme-mimicking nanomaterials, have entered an era of rational design; among them, Co-based nanozymes have emerged as captivating players over times. Co-based nanozymes have been developed and have garnered significant attention over the past five years. Their extraordinary properties, including regulatable enzymatic activity, stability, and multifunctionality stemming from magnetic properties, photothermal conversion effects, cavitation effects, and relaxation efficiency, have made Co-based nanozymes a rising star. This review presents the first comprehensive profiling of the Co-based nanozymes in the chemistry, biology, and environmental sciences. The review begins by scrutinizing the various synthetic methods employed for Co-based nanozyme fabrication, such as template and sol-gel methods, highlighting their distinctive merits from a chemical standpoint. Furthermore, a detailed exploration of their wide-ranging applications in biosensing and biomedical therapeutics, as well as their contributions to environmental monitoring and remediation is provided. Notably, drawing inspiration from state-of-the-art techniques such as omics, a comprehensive analysis of Co-based nanozymes is undertaken, employing analogous statistical methodologies to provide valuable guidance. To conclude, a comprehensive outlook on the challenges and prospects for Co-based nanozymes is presented, spanning from microscopic physicochemical mechanisms to macroscopic clinical translational applications.

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.

A novel sensor based on Ti3C2 MXene/Co3O4/carbon nanofibers composite for the sensitive detection of 4-aminophenol

A novel, sensitive Ti3C2 MXene/Co3O4/carbon nanofibers (Ti3C2 MXene/Co3O4/CNFs) composite was synthesized via a HF exfoliating Ti3AlC2 strategy, followed by doping Co3O4 and Ti3C2 MXene into the CNFs via a combination electrospinning and thermal annealing process. Ti3C2 MXene/Co3O4/CNFs composite exhibits higher catalytic effect, conductivity, chemical stability, and electrochemical performance than Co3O4 and Ti3C2 MXene in electrochemical impedance, differential pulse stripping voltammetry, chronocoulometry, and cyclic voltammetry tests. This Ti3C2 MXene/Co3O4/CNFs hybrid modified electrode provides fast analysis of 4-aminophenol (4-AP) with ultrahigh sensitivity, enhanced reproducibility and strong anti-interference capability. Furthermore, the level of 4-AP was quantified by this electrode with a wide linear range from 0.5 to 150 μM (R2 > 0.99) and a low detection limit about 0.018 μM was achieved. Finally, the fabricated electrode was used for fast and sensitive analysis of 4-AP spiked in tap water and blood serum samples. This work presents the new Ti3C2 MXene/Co3O4/CNFs electrode provides a platform for 4-AP monitoring and has the advantages of high selectivity, accuracy, simplicity, and rapid analysis.

Recent progress in high-performance environmental impacts of the removal of radionuclides from wastewater based on metal-organic frameworks: a review

The nuclear industry is rapidly developing and the effective management of nuclear waste and monitoring the nuclear fuel cycle are crucial. The presence of various radionuclides such as uranium (U), europium (Eu), technetium (Tc), iodine (I), thorium (Th), cesium (Cs), and strontium (Sr) in the environment is a major concern, and the development of materials with high adsorption capacity and selectivity is essential for their effective removal. Metal-organic frameworks (MOFs) have recently emerged as promising materials for removing radioactive elements from water resources due to their unique properties such as tunable pore size, high surface area, and chemical structure. This review provides an extensive analysis of the potential of MOFs as adsorbents for purifying various radionuclides rather than using different techniques such as precipitation, filtration, ion exchange, electrolysis, solvent extraction, and flotation. This review discusses various MOF fabrication methods, focusing on minimizing environmental impacts when using organic solvents and solvent-free methods, and covers the mechanism of MOF adsorption towards radionuclides, including macroscopic and microscopic views. It also examines the effectiveness of MOFs in removing radionuclides from wastewater, their behavior on exposure to high radiation, and their renewability and reusability. We conclude by emphasizing the need for further research to optimize the performance of MOFs and expand their use in real-world applications. Overall, this review provides valuable insights into the potential of MOFs as efficient and durable materials for removing radioactive elements from water resources, addressing a critical issue in the nuclear industry.

Enhancing the catalytic performance of MOF-polymer@AuNP-based nanozymes for colorimetric detection of serum L-cysteine

The dispersion of gold nanoparticles (AuNPs) on a metal-organic framework (MOF) surface greatly affects the catalytic activity of the material. However, regulating the catalytic performance of AuNP-MOF composite-based nanozymes is a great challenge. Herein, poly(dimethylvinyloxazolinone) (PV) was chemically bonded on the surface of UiO-66-NH2 (U66), followed by modification of pepsin (Pep) on the PV chains. U66-PV-Pep@AuNP composite nanozymes were fabricated after the AuNPs formed in situ with Pep as the capping and reducing reagent. Compared to Pep@AuNPs that were physically adsorbed onto the surface of U66, the U66-PV-Pep@AuNP composites exhibited superior peroxidase (POD)-mimetic activity in the oxidation of 3,3'5,5'-tetramethylbenzidine (TMB) with H2O2. Considering the surface dispersion uniformity and local concentration of Pep@AuNPs on the surface of the U66-PV-Pep@AuNP composites, the principle for improving the catalytic performance of the proposed nanozymes was explored. Furthermore, it was observed that the introduction of L-cysteine (L-Cys) into the U66-PV-Pep@AuNP-TMB-H2O2 system significantly reduced its oxidation activity and faded the color, allowing the development of a highly selective and sensitive colorimetric method for L-Cys detection. The UV-vis absorption intensity of oxTMB showed a good linear relationship with the concentration of L-Cys in the range of 2.5-40.0 μM (R2 = 0.996), with a detection limit of 0.33 μM. The proposed protocol using U66-PV-Pep@AuNP nanozymes was applied to monitor rat serum L-Cys following intraperitoneal injection. This study paves the way for the design and construction of MOF-polymer@AuNP nanozymes for drug detection in real bio-samples.

G-/C-rich ssDNA-based Fe and Cu/Fe nanoclusters with peroxidase-like activity for intracellular ROS production and cytotoxicity applications

Five G-/C-rich single-stranded DNA (ssDNA) with different sequences and lengths were templated to prepare the DNA-Cu, DNA-Fe, and bimetallic DNA-Cu/M nanoclusters (NCs). The peroxidase-like activities of these nanomaterials were studied using H₂O₂ and 3,3',5,5''-tetramethylbenzidine (TMB) as the reaction substrates in HAc-NaAc buffer. It was found that T30-G2-Fe NCs and T30-G2-Cu/Fe NCs, with a size of about 2 nm, exhibit similar and the strongest enzyme-like activity under optimal conditions. Both NCs possess a similarly high affinity to substrates, and the Michaelis-Menten constant (K_m) values to TMB and H₂O₂ are about 11 and 2-3 times lower than those of natural horseradish peroxidase (HRP), respectively. The activity of both nanozymes decreases to about 70% after being kept for one week in pH 4.0 buffer at 4 °C, which is comparable with HRP. Hydroxyl radicals (•OH) are the main reactive oxygen species (ROS) produced in the catalytic reaction. Moreover, both NCs can facilitate in situ generation of ROS in HeLa cells using endogenous H₂O₂. MTT assays indicate that the T30-G2-Cu/Fe NCs exhibit the strong selective cytotoxicity to HeLa cells over HL-7702 cells. The cellular viability is about 70% and 50% after incubating with 0.6 M NCs for 24 h without or with 2 mM H₂O₂, respectively. The current study shows that the T30-G2-Cu/Fe NCs have the potential for chemical dynamic treatment (CDT).