A non-enzymatic sensor for hydrogen peroxide based on the use of α-Fe2O3 nanoparticles deposited on the surface of NiO nanosheets

N,N-dicarboxymethyl Perylene-diimide-modified CdV2O6 Nanorods for Colorimetric Sensing of H2O2 and Pyrogallol

The peroxidase-like activity of CdV₂O₆ nanorods has been considerably improved by modification with N, N-dicarboxymethyl perylene-diimide (PDI) as a photosensitizer. The peroxidase-like behaviors are evaluated by virtue of the colorless chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB), which is fast changed into blue oxTMB in the presence of H₂O₂ in only 90 s. PDI-CdV₂O₆ exhibits high stability at elevated temperatures and PDI-CdV₂O₆ retains more than 70% of its catalytic activity over a wide range of 15 to 60 °C. The catalytic mechanism of PDI-CdV₂O₆ is ascribed to the synergistic interaction between PDI and CdV₂O₆ and the generation of •O₂^- radicals. Based on the enhanced peroxidase-like activity of PDI-CdV₂O₆, a selective colorimetric sensor has been constructed for H₂O₂ and pyrogallol (PG) with detection limits of 36.5 μM and 0.179 μM, respectively. The feasibility of the proposed sensing platform has been validated by detecting H₂O₂ in milk and pyrogallol in tap water.

A correlation of conductivity medium and bioparticle viability on dielectrophoresis-based biomedical applications

Dielectrophoresis (DEP) bioparticle research has progressed from micro to nano levels. It has proven to be a promising and powerful cell manipulation method with an accurate, quick, inexpensive, and label-free technique for therapeutic purposes. DEP, an electrokinetic phenomenon, induces particle movement as a result of polarization effects in a nonuniform electrical field. This review focuses on current research in the biomedical field that demonstrates a practical approach to DEP in terms of cell separation, trapping, discrimination, and enrichment under the influence of the conductive medium in correlation with bioparticle viability. The current review aims to provide readers with an in-depth knowledge of the fundamental theory and principles of the DEP technique, which is influenced by conductive medium and to identify and demonstrate the biomedical application areas. The high conductivity of physiological fluids presents obstacles and opportunities, followed by bioparticle viability in an electric field elaborated in detail. Finally, the drawbacks of DEP-based systems and the outlook for the future are addressed. This article will aid in advancing technology by bridging the gap between bioscience and engineering. We hope the insights presented in this review will improve cell suspension medium and promote DEP-viable bioparticle manipulation for health-care diagnostics and therapeutics.

2D Nanomaterial—Based Electrocatalyst for Water Soluble Hydroperoxide Reduction

Hydroperoxides generated on lipid peroxidation are highly reactive compounds, tend to form free radicals, and their elevated levels indicate the deterioration of lipid samples. A good alternative to the classical methods for hydroperoxide monitoring are the electroanalytical methods (e.g., a catalytic electrode for their redox-transformation). For this purpose, a series of metal oxides—doped graphitic carbon nitride 2D nanomaterials—have been examined under mild conditions (pH = 7, room temperature) as catalysts for the electrochemical reduction of two water-soluble hydroperoxides: hydrogen peroxide and tert-butyl hydroperoxide. Composition of the electrode modifying phase has been optimized with respect to the catalyst load and binding polymer concentration. The resulting catalytic electrode has been characterized by impedance studies, cyclic voltammetry and chronoamperometry. Electrocatalytic effect of the Co-g-C3N4/Nafion modified electrode on the electrochemical reduction of both hydroperoxides has been proved by comparative studies. An optimal range of operating potentials from −0.215 V to −0.415 V (vs. RHE) was selected with the highest sensitivity achieved at −0.415 V (vs. RHE). At this operating potential, a linear dynamic range from 0.4 to 14 mM has been established by means of constant-potential chronoamperometry with a sensitivity, which is two orders of magnitude higher than that obtained with polymer-covered electrode.

Preparation of a nonenzymatic electrochemical sensor based on g-C3N4/MWO4 (M: Cu, Mn, ‎Co, Ni) composite for the determination of H2O2‎

‎ Hydrogen peroxide (H2O2) has a significant effect on physiological proceedings. In the ‎present research, a g-C3N4-based nanocomposite g-C3N4/MWO4(M: Cu, Mn, Co, Ni) was ‎prepared via the precipitation-calcination method. A...

Fe3C-Assisted Single Atomic Fe Sites for Sensitive Electrochemical Biosensing

The rational construction of advanced sensing platforms to sensitively detect H₂O₂ produced by living cells is one of the challenges in both physiological and pathological fields. Owing to the extraordinary catalytic performances and similar metal coordination to natural metalloenzymes, single atomic site catalysts (SASCs) with intrinsic peroxidase (POD)-like activity have shown great promise for H₂O₂ detection. However, there still exists an obvious gap between them and natural enzymes because of the great challenge in rationally modulating the electronic and geometrical structures of central atoms. Note that the deliberate modulation of the metal-support interaction may give rise to the promising catalytic activity. In this work, an extremely sensitive electrochemical H₂O₂ biosensor based on single atomic Fe sites coupled with carbon-encapsulated Fe₃C crystals (Fe₃C@C/Fe-N-C) is proposed. Compared with the conventional Fe SASCs (Fe-N-C), Fe₃C@C/Fe-N-C exhibits superior POD-like activity and electrochemical H₂O₂ sensing performance with a high sensitivity of 1225 μA/mM·cm², fast response within 2 s, and a low detection limit of 0.26 μM. Significantly, sensitive monitoring of H₂O₂ released from living cells is also achieved. Moreover, the density functional theory calculations reveal that the incorporated Fe₃C nanocrystals donate electrons to single atomic Fe sites, endowing them with improved activation ability of H₂O₂ and further enhancing the overall activity. This work provides a new design of synergistically enhanced single atomic sites for electrochemical sensing applications.

Synthesis of a CuNP/chitosan/black phosphorus nanocomposite for non-enzymatic hydrogen peroxide sensing

A copper-chitosan-black phosphorus nanocomposite (CuNPs-Chit-BP) was fabricated by electrochemically depositing copper nanoparticles onto a black phosphorus-modified glassy carbon electrode in chitosan solution. CuNPs demonstrated a uniform distribution on the Chit-BP modified GCE with an average size of 20 nm. Electrochemical methods were used to study the catalytic activity of the CuNPs-Chit-BP nanocomposite toward hydrogen peroxide. The results showed that the synthesized nanocomposite exhibited excellent electrical conductivity, good biocompatibility and highly efficient electrocatalytic activity toward hydrogen peroxide reduction in the range of 10 μM-10.3 mM with a detection limit of 0.390 μM. The present work proposed a new strategy to explore novel BP-based non-enzymatic biosensing platforms.

Hetero-structured MnO-Mn3O4@rGO composites: Synthesis and nonenzymatic detection of H2O2

The construction of metal-oxide heterojunction architecture has greatly widened applications in the fields of optoelectronics, energy conversions and electrochemical sensors. In this study, olive-like hetero-structured MnO-Mn₃O₄ microparticles wrapped by reduced graphene oxide (MnO-Mn₃O₄@rGO) were synthesized through a facile solvothermal-calcination treatment. The morphology and structure of MnO-Mn₃O₄@rGO were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction. The as-synthesized MnO-Mn₃O₄@rGO exhibited prominent catalyzing effect on the electroreduction of H₂O₂, due to the combination of good electrical conductivity of rGO and the synergistic effect of MnO and Mn₃O₄. The MnO-Mn₃O₄@rGO modified glassy carbon electrode provided a wide linear response from 0.004 to 17 mM, a low detection limit of 0.1 μM, and high sensitivity of 274.15 μA mM^-1 cm^-2. The proposed sensor displayed noticeable selectivity and long-term stability. In addition, the biosensor has been successfully applied for detecting H₂O₂ in tomato sauce with good recovery, revealing its promising potential applications for practical electrochemical sensors.

Facile Synthesis of ZnMn2O4@rGO Microspheres for Ultrasensitive Electrochemical Detection of Hydrogen Peroxide from Human Breast Cancer Cells

Mixed transition-metal oxides have witnessed increasing attention in catalysts and electrocatalysts. Herein, reduced graphene oxide-wrapped ZnMn₂O₄ microspheres (ZnMn₂O₄@rGO) were facilely synthesized through the solvothermal technique. The microstructure and morphology of ZnMn₂O₄@rGO microspheres were analyzed under Raman, X-ray photoelectron, X-ray diffraction, and energy-dispersive spectroscopies and scanning electron microscopy. The synthesized ZnMn₂O₄@rGO was employed as an excellent electrocatalyst for the reduction of hydrogen peroxide (H₂O₂). The ZnMn₂O₄@rGO-modified glassy carbon electrode (ZnMn₂O₄@rGO/GCE) exhibited a linear detection to H₂O₂ in a wide concentration range of 0.03-6000 μM with a detection limit of 0.012 μM. The biosensor was evaluated to determine H₂O₂ secreted by human breast cancer cells (MCF-7), indicating its promising applications in physiology and diagnosis.

A novel non-enzymatic H2O2 sensor using ZnMn2O4 microspheres modified glassy carbon electrode

With a facile solvothermal technique, ZnMn₂O₄ microspheres were synthesized in this work, which were used as enzyme mimics for the electrocatalytic reduction of H₂O₂. The morphology, crystal phase and structure of the ZnMn₂O₄ microspheres underwent characterization under X-ray diffraction spectroscopy, Raman spectroscopy, energy-dispersive spectroscopy, and scanning electron microscopy. The synthesized ZnMn₂O₄ microspheres showed an average diameter of 2 μm with great crystallinity, and exhibited excellent catalytical activity towards H₂O₂ electroreduction in alkaline media. The glassy carbon electrode modified by ZnMn₂O₄ microspheres showed a linear amperometric response for H₂O₂ in a wide concentration range of 0.02 ˜ 15 mM with detection limit of 0.13 μM under the optimized conditions. Besides, the sensor proposed here was successfully used to determine H₂O₂ in milk, suggesting that ZnMn₂O₄ microspheres can be used for non-enzymatic electrochemical sensor applications.