Au-Au/IrO2@Cu(PABA) Reactor with Tandem Enzyme-Mimicking Catalytic Activity for Organic Dye Degradation and Antibacterial Application

GAA/(Au-Au/IrO2)@Cu(PABA) reactor with cascade catalytic activity for α-glucosidase inhibitor screening

BACKGROUND

In vitro screening strategies based on the inhibition of α-glucosidase (GAA) activity have been widely used for the discovery of potential antidiabetic drugs, but they still face some challenges, such as poor enzyme stability, non-reusability and narrow range of applicability. To overcome these limitations, an in vitro screening method based on GAA@GOx@Cu-MOF reactor was developed in our previous study. However, the method was still not satisfactory enough in terms of construction cost, pH stability, organic solvent resistance and reusability. Thence, there is still a great need for the development of in vitro screening methods with lower cost and wider applicability.

RESULTS

A colorimetric sensing strategy based on GAA/(Au-Au/IrO2)@Cu(PABA) cascade catalytic reactor, which constructed through simultaneous encapsulating Au-Au/IrO2 nanozyme with glucose oxidase-mimicking and peroxidase-mimicking activities and GAA in Cu(PABA) carrier with peroxidase-mimicking activity, was innovatively developed for in vitro screening of GAA inhibitors in this work. It was found that the reactor not only exhibited excellent thermal stability, pH stability, organic solvent resistance, room temperature storage stability, and reusability, but also possessed cascade catalytic performance, with approximately 12.36-fold increased catalytic activity compared to the free system (GAA + Au-Au/IrO2). Moreover, the in vitro GAA inhibitors screening method based on this reactor demonstrated considerable anti-interference performance and detection sensitivity, with a detection limit of 4.79 nM for acarbose. Meanwhile, the method owned good reliability and accuracy, and has been successfully applied to the in vitro screening of oleanolic acid derivatives as potential GAA inhibitors.

SIGNIFICANCE

This method not only more effectively solved the shortcomings of poor stability, narrow scope of application, and non-reusability of natural enzymes in the classical method compared with our previous work, but also broaden the application scope of Au-Au/IrO2 nanozyme with glucose oxidase and peroxidase mimicking activities, and Cu(PABA) carrier with peroxidase mimicking activity, which was expected to be a new generation candidate method for GAA inhibitor screening.

Diagnosis of Mycobacterium tuberculosis using palladium-platinum bimetallic nanoparticles combined with paper-based analytical devices

In this study, we demonstrate that palladium-platinum bimetallic nanoparticles (Pd@Pt NPs) as the nanozyme, combined with a multi-layer paper-based analytical device and DNA hybridization, can successfully detect Mycobacterium tuberculosis. This nanozyme has peroxidase-like properties, which can increase the oxidation rate of the substrate. Compared with horseradish peroxidase, which is widely used in traditional detection, the Michaelis constants of Pd@Pt NPs are fourteen and seventeen times lower than those for 3,3',5,5'-tetramethylbenzidine and H2O2, respectively. To verify the catalytic efficiency of Pd@Pt NPs, this study will execute molecular diagnosis of Mycobacterium tuberculosis. We chose the IS6110 fragment as the target DNA and divided the complementary sequences into the capture DNA and reporter DNA. They were modified on paper and Pd@Pt NPs, respectively, to detect Mycobacterium tuberculosis on a paper-based analytical device. With the above-mentioned method, we can detect target DNA within 15 minutes with a linear range between 0.75 and 10 nM, and a detection limit of 0.216 nM. These results demonstrate that the proposed platform (a DNA-nanozyme integrated paper-based analytical device, dnPAD) can provide sensitive and on-site infection prognosis in areas with insufficient medical resources.

Tailoring the Surface and Composition of Nanozymes for Enhanced Bacterial Binding and Antibacterial Activity

With the advantages of diverse structures, tunable enzymatic activity, and high stability, nanozymes are widely used in medicine, chemistry, food, environment, and other fields. As an alternative to traditional antibiotics, nanozymes attract more and more attention from the scientific researchers in recent years. Developing nanozymes-based antibacterial materials opens up a new avenue for the bacterial disinfection and sterilization. In this review, the classification of nanozymes and their antibacterial mechanisms are discussed. The surface and composition of nanozymes are critical for the antibacterial efficacy, which can be tailored to enhance both the bacterial binding and the antibacterial activity. On the one hand, the surface modification of nanozymes enables binding and targeting of bacteria that improves the antibacterial performance of nanozymes including the biochemical recognition, the surface charge, and the surface topography. On the other hand, the composition of nanozymes can be modulated to achieve enhanced antibacterial performance including the single nanozyme-mediated synergistic and multiple nanozymes-mediated cascade catalytic antibacterial applications. In addition, the current challenges and future prospects of tailoring nanozymes for antibacterial applications are discussed. This review can provide insights into the design of future nanozymes-based materials for the antibacterial treatments.

Amyloid-like nanofibrous network confined and aligned ultrafine bimetallic nanozymes for smart antibacterial therapy

Nanozyme-based antibacterial therapy (NABT) has emerged as a promising strategy to combat bacterial antimicrobial resistance. Engineering the noble metal nanozymes with strong bacterial capture and high catalytic activity for enhanced NABT is highly anticipated but still challenged. Herein, we developed hybrid nanozymes by engineering ultrafine bimetallic Au/Cu nanoparticles confined on the lysozyme amyloid-like nanofibrous networks (LNF). The introduction of copper in the nanozymes facilitates the H2O2 adsorption and reduces the energy barrier for activating the H2O2 decomposition to form •OH, meanwhile displaying the significantly enhanced POD-like activity under NIR irradiation. Taking advantage of the inherent supramolecular networks inspired from human defensin 6-trapping bacteria mechanism, the hybrid nanozymes effectively capture the bacteria and allow the catalytic attack around the bacterial surfaces to improve the antibacterial efficiency. Finally, the as-prepared nanozymes exhibit the preeminent bactericidal efficacy against bacteria, especially for drug-resistant bacteria both in vitro and in vivo, and the effect on wound healing.

One stone, two birds: A Cu-S cluster as a laccase-mimicking nanozyme and sulfite activator for phenol remediation in marine environments

Phenols are infamous pollutants in marine environments and present a grave danger to human health, which makes their efficient detection and removal serious issues. Colorimetry is a simple method for detecting phenols in water because phenols can be oxidized by natural laccase and generate a brown product. However, high cost and poor stability impede the wide-spread implementation of natural laccase in phenol detection. To reverse this adverse situation, a nanoscale Cu-S cluster, Cu₄(MPPM)₄ (Cu₄S₄, MPPM = 2-mercapto-5-n-propylpyrimidine), is synthesized. As a stable and inexpensive nanozyme, Cu₄S₄ shows excellent laccase-mimicking activity and prompts the oxidation of phenols. This characteristic makes Cu₄S₄ a perfect option for phenol detection with colorimetry. In addition, Cu₄S₄ also exhibits sulfite activation properties. It can degrade phenols and other pollutants with advanced oxidation processes (AOPs). Theoretical calculations show good laccase-mimicking and sulfite activation properties originating from appropriate interactions between Cu₄S₄ and substrates. We anticipate that the phenol detection and degradation characteristics of Cu₄S₄ make it a promising material to be used for practical phenol remediation in water environments.

Nanoplexes of ZnS quantum dot-poly-l-lysine/iron oxide nanoparticle-carboxymethylcellulose for photocatalytic degradation of dyes and antibacterial activity in wastewater treatment

The contamination and pollution of wastewater with a wide diversity of chemical, microbiological, and hazardous substances is a field of raising environmental concern. In this study, we developed, for the first time, new hybrid multifunctional nanoplexes composed of ZnS semiconductor quantum dots (ZnS QDs) chemically biofunctionalized with epsilon-poly-l-lysine (ɛPL) and coupled with magnetic iron oxide nanoparticles (MION, Fe₃O₄) stabilized by carboxymethylcellulose (CMC) for the photodegradation (ZnS) of organic molecules and antibacterial activity (ɛPL) with a potential of recovery by an external magnetic field (Fe₃O₄). These nanosystems, which were synthesized entirely through a green aqueous process, were comprehensively characterized regarding their physicochemical properties combined with spectroscopic and morphological features. The results demonstrated that supramolecular colloidal nanoplexes were formed owing to the strong cationic/anionic electrostatic interactions between the biomacromolecule capping ligands of the two nanoconjugates (i.e., polypeptide in ZnS@ɛPL and polysaccharide in Fe₃O₄@CMC). Moreover, these nanosystems showed photocatalytic degradation of methylene blue (MB) used as a model dye pollutant in water. Besides MB, methyl orange, congo red, and rhodamine dyes were also tested for selectivity investigation of the photodegradation by the nanoplexes. The antibacterial activity ascribed to the ɛPL biomolecule was confirmed against Gram-positive and Gram-negative bacteria, including drug-resistance field strains. Hence, it is envisioned that these novel green nanoplexes offer a new avenue of alternatives to be employed for reducing organic pollutants and inactivating pathogenic bacteria in water and wastewater treatment, benefiting from easy magnetic recovery.

Antibody conjugated Au/Ir@Cu/Zn-MOF probe for bacterial lateral flow immunoassay and precise synergistic antibacterial treatment

Staphylococcus aureus is one of the most prevalent threats to public health. Rapid detection with high sensitivity and targeted killing is crucial to curb its spread. Herein, a metal-bearing nanocomposite, consisting of a bimetallic nanoparticle and a metal-organic framework (Au/Ir@Cu/Zn-MOF) was constructed. Upon conjugation with anti-S. aureus antibody, this nanocomposite (Ab-Au/Ir@Cu/Zn-MOF) was exploited for its dual functions, i.e. as a reporting probe in a lateral flow immunoassay and a high efficiency antibacterial reagent. Benefiting from the enrichment of Au/Ir NPs by the Cu/Zn-MOF, the Au/Ir@Cu/Zn-MOF-based lateral flow immunoassay sensor exhibited a visual limit of detection of 10³ CFU/mL, which was100 times more sensitive than Au/Ir-based sensor. Moreover, the Ab-Au/Ir@Cu/Zn-MOF probe possessed synergistic photothermal-chemodynamic bactericidal effect that specifically targeted against S. aureus. Under a co-treatment by H₂O₂ (0.4 mM) and 808 nm near infrared irradiation (1 W/cm², 5 min), complete sterilization of 5 × 10⁵-10⁶ CFU/mL S. aureus was achieved at a nanocomposite concentration as low as 6.25 μg/mL. The superior antibacterial efficiency was attributable to the three-fold properties of the Ab-Au/Ir@Cu/Zn-MOF probe: (1) enhanced multi-enzyme mimicking activities that promote reactive oxygen species generation, (2) high photothermal activity (efficiency of 53.70%), and (3) bacteria targeting ability via the antibody coating. By changing the antibody, this nanocomposite can be tailored to target a wide range of bacteria species, for detection and for precise antibacterial treatment.

Carbon Dots-Based Nanozyme for Drug-Resistant Lung Cancer Therapy by Encapsulated Doxorubicin/siRNA Cocktail

Background

Nanomaterials exhibited intrinsic enzyme-like properties due to the unique properties compared with natural enzyme. Carbon dots (CDs) are an important kind of quantum-sized nanomaterials, which have enormous application potential in bio-imaging, drug carrier, and nanosystems. Carbon dots possess intrinsic enzyme-like properties, such as glutathione (GSH) oxidase or peroxidase activities.

Methods

A co-delivery nanosystem that could carry siRNA and doxorubucin (DOX) simultaneously has been studied in this work. The co-delivery based on carbon dots was surface-modified with poly-ethylenimine (PEI) and loaded the siMRP1 with chemotherapeutics on the surface with pH-triggered drug release. The CD-PEI was synthesized by one-step microwave assisted method; the PEI was raw materials and passivator during the reaction process that makes CDs exhibit excellent optical property.

Results

The CD-PEI was capable of loading and delivering siMRP1 and DOX to tumors and releasing them synchronously in cells in an acid-triggered manner. The particles exhibited GSH oxidase-like catalytic property, oxidizing GSH to oxidized glutathione with concomitant increase of reactive oxygen species (ROS). We found that silencing of MRP1 by co-delivery system antagonized chemoresistance by increasing DOX accumulation and significantly enhancing the inhibitory effect of cell viability induced by CD-PEI-DOX. The co-delivery system dramatically inhibited tumor growth in xenograft model, and CDs counteracted MRP1 function by siRNA-mediated knockdown of MRP1.

Conclusion

Taken together, we uncover the potential role of CDs with a combination of siRNA and chemotherapeutics in overcoming chemoresistance of lung cancer by suppressing MRP1 and oxidation of GSH. Our findings imply its potential of antagonizing chemoresistance to enhance therapeutic efficiency of doxorubicin in clinical practices of lung cancer treatment.

Recent advances in bioremediation of heavy metals and persistent organic pollutants: A review

Heavy metals and persistent organic pollutants are causing detrimental effects on the environment. The seepage of heavy metals through untreated industrial waste destroys the crops and lands. Moreover, incineration and combustion of several products are responsible for primary and secondary emissions of pollutants. This review has gathered the remediation strategies, current bioremediation technologies, and their primary use in both in situ and ex situ methods, followed by a detailed explanation for bioremediation over other techniques. However, an amalgam of bioremediation techniques and nanotechnology could be a breakthrough in cleaning the environment by degrading heavy metals and persistant organic pollutants.

Emerging nanozyme-based multimodal synergistic therapies in combating bacterial infections

Pathogenic infections have emerged as major threats to global public health. Multidrug resistance induced by the abuse of antibiotics makes the anti-infection therapies to be a global challenge. Thus, it is urgent to develop novel, efficient and biosafe antibiotic alternatives for future antibacterial therapy. Recently, nanozymes have emerged as promising antibiotic alternatives for combating bacterial infections. More significantly, the multimodal synergistic nanozyme-based antibacterial systems open novel disinfection pathways. In this review, we are mainly focusing on the recent research progress of nanozyme-based multimodal synergistic therapies to eliminate bacterial infections. Their antibacterial mechanism, the synergistic antibacterial systems are systematically summarized and discussed according to the combination of mechanisms and the purpose to improve their antibacterial efficiency, biosafety and specificity. Finanly, the current challenges and prospects of the multimodal synergistic antibacterial systems are proposed.

Metal-organic frameworks with peroxidase-like activity for efficient removal of aflatoxin B1

Aflatoxin B₁ (AFB₁), a naturally produced toxin existing in major food crops, is highly toxic and carcinogenic to human and animals. In this study, a reusable material, Pd@PCN-222 with great adsorption performance and peroxidase-like activity was synthesized for the removal of AFB₁. Pd@PCN-222 exhibited great adsorption performance owing to hierarchical porous structure. Pd@PCN-222 also could catalyze the AFB₁ in the presence of H₂O₂ due to the Fe-tetrakis (4-carboxyphenyl) porphyrin and Pd as effective peroxidase active site, which improved the removal efficiency of AFB₁. Pd@PCN-222 was applied for the removal of AFB₁ with a removal rate of 96.52% in 2 h. Owing to the advantages of high removal efficiency and reusability, Pd@PCN-222 had great application potential in AFB₁ removal.

In Situ Growth of a Metal-Organic Framework on Graphene Oxide for the Chemo-Photothermal Therapy of Bacterial Infection in Bone Repair

Bacterial infection with high morbidity (>30%) seriously affects the defect's healing after bone transplantation. To this end, chemotherapy and photothermal therapy have been utilized for antibacterial treatment owing to their high selectivity and minimal toxicity. However, they also face several dilemmas. For example, bacterial biofilms prevented the penetration of antibacterial agents and local temperatures (over 70 °C) caused by the photothermal therapy damaged normal tissue. Herein, a co-dispersion nanosystem with chemo-photothermal function was constructed via the in situ growth of zeolitic imidazolate framework-8 (ZIF-8) on graphene oxide (GO) nanosheets. In this nanosystem, GO generates a local temperature (∼50 °C) to increase the permeability of a bacterial biofilm under near-infrared laser irradiation. Then, Zn ions released by ZIF-8 seized this chance to react with the bacterial membrane and inactivate it, thus realizing efficient sterilization in a low-temperature environment. This antibacterial system was incorporated into a poly-l-lactic acid scaffold for bone repair. Results showed that the scaffold showed a high antibacterial rate of 85% against both Escherichia coli and Staphylococcus aureus. In vitro cell tests showed that the scaffold promoted cell proliferation.

Washable Patches with Gold Nanowires/Textiles in Wearable Sensors for Health Monitoring

Textile-based flexible electronic devices have attracted tremendous attention in wearable sensors due to their excellent skin affinity and conformability. However, the washing process of such devices may damage the electronic components. Here, a textile-based piezoresistive sensor with ultrahigh sensitivity was fabricated through the layered integration of gold nanowire (AuNW)-impregnated cotton fabric and silver ink screen-printed nylon fabric electrodes, sealing with Parafilm. The prepared piezoresistive sensing patch exhibits outstanding performance, including high sensitivity (914.970 kPa^-1, <100 Pa), a fast response time (load: 38 ms, recovery: 34 ms), and a low detection limit (0.49 Pa). More importantly, it can maintain a stable signal output even after 30 000 s of loading-unloading cycles. Furthermore, this sensing patch can efficiently detect breathing, pulse, heart rate, and joint movements during the activities. After five cycles of mechanical washing, the piezoresistive performance keeps 90.3%, demonstrating the high feasibility of this sensor in practical applications. This sensor has a simple fabrication, with good fatigue resistance and durability due to its all-fabric core element. It provides a strategy to address the machine-washing issues in textile electronics. This washable textile sensor is expected to show significant potential in future applications of health monitoring, human-machine interfaces, and artificial skin.

Nanozybiotics: Nanozyme-Based Antibacterials against Bacterial Resistance

Infectious diseases caused by bacteria represent a global threat to human health. However, due to the abuse of antibiotics, drug-resistant bacteria have evolved rapidly and led to the failure of antibiotics treatment. Alternative antimicrobial strategies different to traditional antibiotics are urgently needed. Enzyme-based antibacterials (Enzybiotics) have gradually attracted interest owing to their advantages including high specificity, rapid mode-of-action, no resistance development, etc. However, due to their low stability, potential immunogenicity, and high cost of natural enzymes, enzybiotics have limitations in practical antibacterial therapy. In recent years, many nanomaterials with enzyme-like activities (Nanozymes) have been discovered as a new generation of artificial enzymes and perform catalytic antibacterial effects against bacterial resistance. To highlight the progress in this field of nanozyme-based antibacterials (Nanozybiotics), this review discussed the antibacterial mechanism of action of nanozybiotics with a comparison with enzybiotics. We propose that nanozybiotics may bear promising applications in antibacterial therapy, due to their high stability, rapid bacterial killing, biofilm elimination, and low cost.

Metal–organic-framework-based photocatalysts for microorganism inactivation: a review

A metal–organic framework (MOF) is a porous coordination material composed of multidentate organic ligands and metal ions or metal clusters.