The peroxidase/catalase-like activities of MFe₂O₄ (M=Mg, Ni, Cu) MNPs and their application in colorimetric biosensing of glucose

Ultrasmall Pt Nanoclusters as Robust Peroxidase Mimics for Colorimetric Detection of Glucose in Human Serum

In this work, a new type of ultrasmall Pt nanoclusters (Pt NCs) was prepared via a facile one-pot approach by using yeast extract as the reductant and stabilizer. Besides their excellent water solubility, these yeast extract-stabilized Pt NCs also possess attractive peroxidase mimicking property. They can efficiently catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the coexistence of hydrogen peroxide (H₂O₂). Catalytic mechanism analysis suggested that the peroxidase mimicking activity of these Pt NCs might originate from their characteristic of accelerating electron transfer between TMB and H₂O₂, and their enzymatic kinetics followed typical Michaelis-Menten theory. On the basis of these findings, we developed a new highly sensitive colorimetric method for glucose detection, and the limit of detection was calculated as low as 0.28 μM (S/N = 3). Further application of the present system for glucose detection in human serum has been successfully demonstrated, suggesting its promising utilization as robust peroxidase mimics in the clinical diagnosis, pharmaceutical, and environmental chemistry fields.

Peroxidase activity of the coronene bisimide supramolecular architecture and its applications in colorimetric sensing of H2O2 and glucose

A new water soluble coronene bisimide derivative (CTDI) was designed and synthesized. CTDI self-assembled in an aqueous solution and formed supramolecular nanofibers through π-π stacking and hydrophobic interactions. The nanofibers exhibit distinct peroxidase-like catalytic activity, and can catalyze the redox reaction of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide. Clear assay solution color changes were observed. The peroxidase-like catalytic property was utilized for the sensitive detection of H₂O₂ and glucose. The assay shows excellent sensitivity, and 1 μM of glucose could be easily detected. Glucose detection in dilute human blood samples was also demonstrated, and the results were verified using a commercial glucose meter. Our method is simple, convenient, sensitive and selective, and could facilitate the sensing of glucose in relation to biological and biomedical research applications.

One-Pot Synthesis of Fe3O4 Nanoparticle Loaded 3D Porous Graphene Nanocomposites with Enhanced Nanozyme Activity for Glucose Detection

A novel one-pot strategy is proposed to fabricate 3D porous graphene (3D GN) decorated with Fe₃O₄ nanoparticles (Fe₃O₄ NPs) by using hemin as iron source. During the process, graphene oxide was simultaneously reduced and self-assembled to form 3D graphene hydrogel while Fe₃O₄ NPs synthesized from hemin distributed uniformly on 3D GN. The preparation process is simple, facile, economical, and green. The obtained freeze-dried product (3D GH-5) exhibits outstanding peroxidase-like activity. Compared to the traditional 2D graphene-based nanocomposites, the introduced 3D porous structure dramatically improved the catalytic activity, as well as the catalysis velocity and its affinity for substrate. The high catalytic activity could be ascribed to the formation of Fe₃O₄ NPs and 3D porous graphene structures. Based on its peroxidase-like activity, 3D GH-5 was used for colorimetric determination of glucose with a low detection limit of 0.8 μM.

Colorimetric detection of glucose based on gold nanoparticles coupled with silver nanoparticles

We have coupled gold nanoparticles (AuNPs) with silver nanoparticles (AgNPs) to assemble a plasmonic sensing platform for colorimetric detection of glucose. In this system, small AuNPs (~4nm) can act as glucose oxidase (GOD) mimic enzyme to catalytically oxidize glucose in the presence of oxygen, producing hydrogen peroxide, which dissolves AgNPs to lead the color changes. Glucose can be detected not only by naked eyes (from yellow to red) but also by spectrophotometer in the concentration range of 5-70μM, with detection limit of 3μM. More importantly, we found that l-cysteine added in the system can markedly improve the selectivity for the detection of glucose. The proposed method was used to application for the detection of glucose in human serum with satisfactory results. This system is simple and low cost without using any enzymes and organic chromogenic agents.

Strategies to reduce the intracellular effects of iron oxide nanoparticle degradation

Mesenchymal stem cells (MSCs) have a significant self-renewal capacity and can differentiate into a variety of cell types. Cell labeling is crucial as it is difficult to detect cell fate after transplantation in vivo. MSCs labeled with iron oxide nanoparticles (IONPs), which can be tracked by MRI, have tremendous potential in regenerative medicine and oncological research. As a part of nanoparticle, the iron oxide core is a key aspect that can exhibit adverse or beneficial effects on MSCs labeled for tracking. Some IONPs exhibit adverse effects, such as cytotoxicity and apoptosis, while other IONPs exhibit beneficial functions that can promote both MSC proliferation and homing efficiency. This review reveals the cytotoxic mechanisms and potential functions of the iron oxide core of IONPs in cell labeling as well as strategies for minimizing the intracellular effects of IONPs.

Hierarchical NiCo₂O₄ Hollow Sphere as a Peroxidase Mimetic for Colorimetric Detection of H₂O₂ and Glucose

In this work, the hierarchical NiCo₂O₄ hollow sphere synthesized via a “coordinating etching and precipitating” process was demonstrated to exhibit intrinsic peroxidase-like activity. The peroxidase-like activity of NiCo₂O₄, NiO, and Co₃O₄ hollow spheres were comparatively studied by the catalytic oxidation reaction of 3,3,5,5-tetramethylbenzidine (TMB) in presence of H₂O₂, and a superior peroxidase-like activity of NiCo₂O₄ was confirmed by stronger absorbance at 652 nm. Furthermore, the proposed sensing platform showed commendable response to H₂O₂ with a linear range from 10 μM to 400 μM, and a detection limit of 0.21 μM. Cooperated with GOx, the developed novel colorimetric and visual glucose-sensing platform exhibited high selectivity, favorable reproducibility, satisfactory applicability, wide linear range (from 0.1 mM to 4.5 mM), and a low detection limit of 5.31 μM. In addition, the concentration-dependent color change would offer a better and handier way for detection of H₂O₂ and glucose by naked eye.

Perovskite LaCoO3 nanoparticles as enzyme mimetics: their catalytic properties, mechanism and application in dopamine biosensing

The perovskite nanomaterial LaCoO₃ was found to exhibit enzyme-like activities, which are new properties of perovskite materials in the catalytic field.

A facile one-pot synthesis of cobalt-doped magnetite/graphene nanocomposite as peroxidase mimetics in dopamine detection

Cobalt-doped magnetite/graphene nanocomposites (Co-MGNCs) were prepared by a facile one-pot electrochemical method.

Oxidase-mimicking activity of the nitrogen-doped Fe3C@C composites

The nitrogen-doped Fe₃C@C composites could behave as oxidase-mimics to catalyze the reaction between TMB and molecular oxygen to produce quinonediimine and H₂O.

Triple-enzyme mimetic activity of nickel-palladium hollow nanoparticles and their application in colorimetric biosensing of glucose

We demonstrate that nickel-palladium hollow nanoparticles (NiPd hNPs) exhibit triple-enzyme mimetic activity: oxidase-like activity, peroxidase-like activity and catalase-like activity. As peroxidase mimetics, the catalytic activity of NiPd hNPs was investigated in detail. On this basis, a simple glucose biosensor with a wide linear range and low detection limit was developed.

Stability, Scalability, and Reusability of a Volume Efficient Biocatalytic System Constructed on Magnetic Nanoparticles

This report investigates for the first time stability, scalability, and reusability characteristics of a protein nano-bioreactor useful for green synthesis of fine chemicals in aqueous medium extracting maximum enzyme efficiency. Enzyme catalysts conjugated with magnetic nanomaterials allow easy product isolation after a reaction involving simple application of a magnetic field. In this study, we examined a biocatalytic system made of peroxidase-like myoglobin (Mb), as a model protein, to covalently conjugate with poly(acrylic acid) functionalized magnetic nanoparticles (MNPs, 100 nm hydrodynamic diameter) to examine the catalytic stability, scalability, and reusability features of this bioconjugate. Application of the conjugate was effective for electrochemical reduction of organic and inorganic peroxides, and for both peroxide-mediated and electrocatalytic oxidation of the protein substrate 2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) with greater turnover rates and product yields than Mb prepared in solution or MNP alone. Mb-attached MNPs displayed extensive catalytic stability even after 4 months of storage compared to Mb present in solution. Five- and ten-fold scale up of MNPs in the bioconjugates resulted in two- and four-fold increases in protein-catalyzed oxidation products, respectively. Nearly 40% of the initial product was present even after four reuses, which is advantageous for synthesizing sufficient products with a minimal investment of precious enzymes. Thus, the results obtained in this study are highly significant in guiding cost-effective development and efficient multiple uses of enzyme catalysts for biocatalytic, electrocatalytic, and biosensing applications via magnetic nanomaterials conjugation.

Catalytic Oxidation of Hydroquinone in Aqueous Solution over Bimetallic PdCo Catalyst Supported on Carbon: Effect of Interferents and Electrochemical Measurement

Palladium-cobalt alloy nanoparticles were synthesized and dispersed on carbon black support, aiming to have a less expensive catalyst. Catalytic behaviors of PdCo/C catalyst for the oxidation of hydroquinone (HQ) with H2O2 in aqueous solution were evaluated using high-performance liquid chromatography (HPLC). The results revealed that PdCo/C catalyst had better catalytic activity than an equal amount of commercial Pd/C and Co/C catalysts because of the d-band hybridization between Pd and Co. The effects of pH value, solvent, and various interferents including inorganic and organic compounds on the efficiency of HQ oxidation were further investigated. Furthermore, on the basis of mixed potential theory, comprehensive electrochemical measurements such as the open-circuit potential-time (OCP-t) technique and Tafel plot were efficient to assess the catalytic activity of the catalyst, and the results obtained were consistent with those of HPLC measurements. The efficient HQ oxidation was closely associated with the catalytic activity of PdCo nanoparticles because they accelerated the electron-transfer process and facilitated the generation of OH radicals.

Triple-enzyme mimetic activity of Co3O4 nanotubes and their applications in colorimetric sensing of glutathione

Based on the oxidase-like activity of Co₃O₄ nanotubes, a simple and sensitive colorimetric sensor for GSH detection was investigated.

Dual enzyme mimicry exhibited by ITO nanocubes and their application in spectrophotometric and electrochemical sensing

Schematic illustration of the peroxidase/catalase-like activities of ITO nanocubes.

Nanozymes in bionanotechnology: from sensing to therapeutics and beyond

Nanozymes are nanomaterials with enzyme-like characteristics, which have found broad applications in various areas including bionanotechnology and beyond.

A facile one-pot solvothermal synthesis of CoFe2O4/RGO and its excellent catalytic activity on thermal decomposition of ammonium perchlorate

A novel catalyst CoFe₂O₄/RGO has been synthesized and shows enhanced catalytic activity on thermal decomposition of ammonium perchlorate.

Fabrication of cuprous sulfide nanorods supported on copper foam for nonenzymatic amperometric determination of glucose and hydrogen peroxide

Cuprous sulfide nanothorns were fabricated on copper foam for nonenzymatic amperometric determination of glucose and hydrogen peroxide.

Sphere-like CoS with nanostructures as peroxidase mimics for colorimetric determination of H2O2 and mercury ions

CoS, which was prepared using a facile solvothermal method, and characterized using various analytical techniques, was demonstrated for the first time to exhibit intrinsic peroxidase-like activity.

Functional nanostructures for enzyme based biosensors: properties, fabrication and applications

A review describing functional nanostructures for portable and printable enzyme biosensors. Specific physicochemical and surface properties of nanoparticles used as carriers and sensing components and their assembly are discussed with an overview of current and emerging techniques enabling large scale roll-to-roll fabrication and miniaturization. Their integration in flexible, wearable and inexpensive point-of-use devices, and implementation challenges are also provided with examples of applications.

Biomedical Probes Based on Inorganic Nanoparticles for Electrochemical and Optical Spectroscopy Applications

Inorganic nanoparticles usually provide novel and unique physical properties as their size approaches nanometer scale dimensions. The unique physical and optical properties of nanoparticles may lead to applications in a variety of areas, including biomedical detection. Therefore, current research is now increasingly focused on the use of the high surface-to-volume ratios of nanoparticles to fabricate superb chemical- or biosensors for various detection applications. This article highlights various kinds of inorganic nanoparticles, including metal nanoparticles, magnetic nanoparticles, nanocomposites, and semiconductor nanoparticles that can be perceived as useful materials for biomedical probes and points to the outstanding results arising from their use in such probes. The progress in the use of inorganic nanoparticle-based electrochemical, colorimetric and spectrophotometric detection in recent applications, especially bioanalysis, and the main functions of inorganic nanoparticles in detection are reviewed. The article begins with a conceptual discussion of nanoparticles according to types, followed by numerous applications to analytes including biomolecules, disease markers, and pharmaceutical substances. Most of the references cited herein, dating from 2010 to 2015, generally mention one or more of the following characteristics: a low detection limit, good signal amplification and simultaneous detection capabilities.

Anisotropic gold nanoparticles for the highly sensitive colorimetric detection of glucose in human urine

PEDOT:PSS modified anisotropic gold nanoparticles (GNP) for the colorimetric detection of glucose in urine.

Catalytic decomposition action of hollow CuFe2O4 nanospheres on RDX and FOX-7

Hollow CuFe₂O₄ nanospheres show high catalytic activity on the thermal decomposition of RDX and FOX-7.

In situ growth of metallic silver on glucose oxidase for a highly sensitive glucose sensor

A bio-composite was assembled by in situ reducing Ag⁺ to Ag in glucose oxidase solution and used to detect glucose.