μM For H2O2 Research Articles

Nanozyme-Catalyzed Colorimetric Detection of the Total Antioxidant Capacity in Body Fluids by Paper-Based Microfluidic Chips.

Total antioxidants play a crucial role in human health, and detection of the total antioxidant capacity (TAC) has broad application prospects in fields such as food safety, environmental assessment, and disease diagnosis. However, a long detection time, cumbersome steps, high cost, reliance on professional equipment, and nonportability still remain significant challenges. In this work, an efficient strategy of point-of-care testing (POCT) of the TAC in body fluids by nanozyme-catalyzed colorimetric paper-based microfluidic sensors is proposed. The paper-based microfluidic sensors coupled with a smartphone can reduce testing costs and provide portability. The nanozyme prepared by the solvothermal method presents Michaelis constants of 0.11 and 0.129 mM for H2O2 and TMB, respectively. A method for immobilizing nanozymes and chromogenic agents on a paper-based microfluidic chip is established. Based on smartphone photography and image grayscale extraction, the TAC can be qualitatively detected with a detection limit and linear range of 33.4 and 50-700 μM, respectively. Furthermore, the proposed sensor can realize the one-step quantitative analysis of the TAC in body fluids (blood, saliva, and sweat) within 15 min. The proposed nanozyme-catalyzed colorimetric paper-based microfluidic sensors presented in this study exhibit promising application prospects in the fields of biochemical analysis and POCT.

Bimetal−organic framework-integrated electrochemical sensor for on-chip detection of H2S and H2O2 in cancer tissues

Studies on the interaction between hydrogen sulfide (H2S) and hydrogen peroxide (H2O2) in redox signaling motivate the development of a sensitive sensing platform for their discriminatory and dynamic detection. Herein, we present a fully integrated microfluidic on-chip electrochemical sensor for the online and simultaneous monitoring of H2S and H2O2 secreted by different biological samples. The sensor utilizes a cicada-wing-like RuCu bimetal−organic framework with uniform nanorods architecture that grows on a flexible carbon fiber microelectrode. Owing to the optimized electronic structural merits and satisfactory electrocatalytic properties, the resultant microelectrode shows remarkable electrochemical sensing performance for sensitive and selective detection of H2S and H2O2 at the same time. The result exhibits low detection limits of 0.5 μM for H2S and 0.1 μM for H2O2, with high sensitivities of 61.93 μA cm−2 mM−1 for H2S, and 75.96 μA cm−2 mM−1 for H2O2. The integration of this biocompatible microelectrode into a custom wireless microfluidic chip enables the construction of a miniature intelligent system for in situ monitoring of H2S and H2O2 released from different living cells to differentiate between cancerous and normal cells. When applied for real-time tracking of H2S and H2O2 secreted by colorectal cancer tissues, it allows the evaluation of their chemotherapeutic efficacy. These findings hold paramount implications for disease diagnosis and therapy.

Facile Synthesis of Copper Telluride Nanoparticles as a Robust Nanoenzymatic Catalyst for Intrinsic Peroxidase‐Like Activity

AbstractCopper telluride nanoparticles are classified as the family of metal chalcogenides and were synthesized using a simple solvothermal method using a new source of telluride, ditelluride diphenyl. The characterized techniques revealed that the atomic composition of copper tellurides is Cu2Te and particles are spherical. This study is greatly examined by different designed experiments for the proof of the intrinsic peroxidase‐like activity of copper telluride nanoparticles and its effectiveness in a variety of similar structures. Cu2Te nanoparticles can convert peroxidase substrates (TMB and OPD) to colored products in the presence of H2O2. In addition, the as‐prepared nanoparticles have the potential to oxidize DPPH and ABTS substrates. Michaelis–Menten constant KM value for TMB and H2O2 was found to be 12 mM and 0.60 mM for H2O2 and the Vmax value of the Cu2Te was found to be TMB and H2O2 was 2.50×10−7 and 0.82×10−8 MS−1. These data are found to be almost comparable with natural peroxidase HRP and other artificial enzymes reported in the literature. The natural peroxidase‐like activities of Cu2Te nanoparticles originated from the catalytic decomposition of H2O2 into ⋅OH radical, which was confirmed from the ESR spin‐trapping technique and using a fluorescence probe, terephthalic acid.

Au/Ag2MoO4 nanocomposite: A dual-function catalyst for dye degradation and colorimetric detection

The authors have successfully synthesized a distinctive potato-shaped Au/Ag2MoO4 nanocomposite with exceptional photocatalytic capabilities in the degradation of methylene blue (MB) under UV irradiation even in neutral conditions. Furthermore, this material displays noteworthy peroxidase-like oxidation activity, facilitating the detection of hydrogen peroxide (H2O2) and ascorbic acid (AA) in aqueous environments. This detection method relies on the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB). The signal generated by TMB adsorption on the catalyst's surface plays a pivotal role in the oxidation of TMB in the presence of H2O2, resulting in the formation of a distinct blue-colored product. This reaction is equally influenced by the presence of AA, which, owing to its antioxidant properties, impedes the development of the color signal. This colorimetric approach exhibits high sensitivity, boasting low limits of detection (LOD) and quantification (LOQ) of 0.0252 and 0.0839 mM for H2O2, and 1.7724 and 5.7109 mg/L for AA, respectively. The method offers a broad linear range spanning from 0.029 to 26.47 mM for H2O2 and 0–40 mg/L for AA with a straightforward, cost-effective analytical procedure, and yields highly reliable results. The proposed method displays superior selectivity in detecting AA and high anti-interference capabilities. These findings underscore the photocatalytic and peroxidation-like activities of Au/Ag2MoO4 nanocomposite, positioning it as a promising candidate for various biomedical applications.

Nanozyme-assisted molecularly imprinted polymer-based indirect competitive ELISA for the detection of marine biotoxin

Saxitoxin (STX), which is produced by certain dinoflagellate species, is a type of paralytic shellfish poisoning toxin that poses a serious threat to human health and the environment. Therefore, developing a technology for the convenient and cost-effective detection of STX is imperative. In this study, we developed an affinity peptide-imprinted polymer-based indirect competitive ELISA (ic-ELISA) without using enzyme–toxin conjugates. AuNP/Co3O4@Mg/Al cLDH was synthesized by calcining AuNP/ZIF-67@Mg/Al LDH, which was obtained by combining AuNPs, ZIF-67, and flower-like Mg/Al LDH. This synthesized nanozyme exhibited high catalytic activity (Km = 0.24 mM for TMB and 132.5 mM for H2O2). The affinity peptide-imprinted polymer (MIP) was imprinted with an STX-specific template peptide (STX MIP) on a multi-well microplate and then reacted with an STX-specific signal peptide (STX SP). The interaction between the STX SP and MIP was detected using a streptavidin-coated nanozyme (SA-AuNP/Co3O4@Mg/Al cLDH). The developed MIP-based ic-ELISA exhibited excellent selectivity and sensitivity, with a limit of detection of 3.17 ng/mL (equivalent: 0.317 μg/g). Furthermore, the system was validated using a commercial ELISA kit and mussel tissue samples, and it demonstrated a high STX recovery with a low coefficient of variation. These results imply that the developed ic-ELISA can be used to detect STX in real samples.

Fabrication of a laser-directed electrochemical paper analytical device and its deployment for multi-functional electrochemical sensing

The demand for eco-friendly, disposable, and affordable electrochemical sensors stimulates the fabrication of laser-directed paper-based electrodes. This work reports the fabrication of laser-derived patterns on the paper substrate and its multi-functional sensing applications. For this, a computer-aided design (CAD) software-driven computer numerical control (CNC) manufacturing method was developed to engrave a three-electrode design on a paper substrate. The fabricated Laser-Directed electrochemical Paper Analytical Device (LD-ePAD) was thoroughly characterized by Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), contact angle analysis, electrochemical impedance spectroscopy (EIS), and the cyclic voltammetry (CV). After that, we demonstrated the multi-functional sensing ability of the LD-ePADs by detecting diverse model analytes, including small molecules (i.e., lead ions [Pb2+]), free radicals (i.e., peroxide [H2O2]), and macromolecules (i.e., Alkaline phosphatase [ALP]). Upon investigation, it exhibits a fair detection limit of 5.19 (±0.21) µM for Pb2+, 48.66 (±0.31) µM for H2O2, and 0.48 (±0.02) U/L for ALP. The LD-ePADs' outstanding repeatability, stability, abundance of catalytic active sites, remarkable tunability, and potential for nano-bioengineering emphasized their tremendous commercial feasibility. To the best of our knowledge, this is the first study to use controlled one-step laser direct engraving to fabricate a three-electrode setup on a paper-substrate that can sense three heterogeneous molecules electrochemically.

Highly efficient persistent luminescent nanozymes-based luminescence-colorimetric dual-mode sensor for total antioxidant capacity assay

Total antioxidant capacity (TAC) is a vital parameter to assess the gross antioxidant activity in biological and food matrices. Accurate determination of TAC has become increasingly important for health monitoring and dietary guidance. Here, we report a persistent luminescent nanozyme (ZGO-Pt) based luminescence-colorimetric dual-mode sensor for selective determination of TAC. ZGO-Pt was fabricated based on ZnGa2O4:Cr nanoparticles (ZGO) with platinum nanoflower as synthetic additive. The prepared ZGO-Pt exhibited fascinating peroxidase-mimetic activity and persistent luminescence, and enabled effectively catalysis of the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxTMB. Meanwhile, the generated oxTMB gave strong absorption at 652 nm to quench the luminescence of ZGO-Pt at 700 nm via the inner filter effect. Antioxidants could compete with the oxidable TMB or reduce oxTMB to TMB, resulting in the simultaneous variations of blue color and luminescence to provide the basis for dual-mode assay for TAC. The highly efficient catalysis of ZGO-Pt (Km, 3.12 mM for H2O2, 0.592 mM for TMB) allows the dual-mode sensor to realize precise determination of TAC with a wide linear range (0.5–200 μM and 1–300 μM for colorimetric and luminescence mode, respectively) and low limit of detection (LOD, 0.05 μM and 0.78 μM for colorimetric and luminescence mode, respectively). The developed dual-mode sensor was successfully applied to the determination of TAC in vitamin tablet, beverages and fruits. This work provides an efficient persistent luminescent nanoparticle-based nanozyme for a facile TAC assay with further vision in biosensing and food technology.

Microwave-assisted synthesis of Limonia acidissima Groff gum stabilized palladium nanoparticles for colorimetric glucose sensing

Herein, we present a novel microwave-assisted method for the synthesis of palladium nanoparticles (PdNPs) supported by Limonia acidissima Groff tree extract gum. The synthesized PdNPs were characterized using various analytical techniques, including FTIR, SEM, TEM, UV–visible, and powder XRD analyses. TEM and XRD analysis confirmed that the synthesized LAG-PdNPs are highly crystalline nature spherical shapes with an average size diameter of 7–9 nm. We employed these gum-capped PdNPs to investigate their peroxidase-like activity for colorimetric detection of hydrogen peroxide (H2O2) and glucose. The oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2, catalyzed by PdNPs, produces oxidation products quantified at 652 nm using spectrophotometry. The catalytic activity of PdNPs was optimized with respect to temperature and pH. The developed method exhibited a linear range of detection from 1 to 50 µm, with detection limits of 0.35 µm for H2O2 and 0.60 µm for glucose.

Dual-functional PCN-242 (Fe2Co) MOF for sensitive bacterial endotoxin detection.

Endotoxin detection is paramount for monitoring bacterial contamination in food, pharmaceuticals, and clinical diagnostics. The limulus amebocyte lysate (LAL) test, which relies on horseshoe crab blood, has long been the gold standard for endotoxin detection. However, the widespread adoption of this method is constrained by ethical concerns and the high costs associated with harvesting endangered species. Although nanozyme-based colorimetric methods present a more cost-effective and straightforward alternative, their application is limited by suboptimal selectivity and sensitivity. In this study, we report the synthesis and rigorous characterization of the bimetallic PCN-242 (Fe2Co) metal-organic framework (MOF), synthesized using 2-amino terephthalic acid and a pre-synthesized [Fe2Co(μ3-O)(CH3COO)6] cluster. Steady-state kinetic analyses revealed that PCN-242 (Fe2Co) MOF exhibits a significantly higher affinity for hydrogen peroxide (H2O2) compared to horseradish peroxidase (HRP) and other iron-based MOFs. The development of a PCN-242 (Fe2Co)-based colorimetric sensor demonstrated a low limit of detection (LOD) of 1.36 μg mL-1 for endotoxins, with excellent selectivity and reproducibility, thereby enabling effective detection of bacterial endotoxins. Recognizing the potential of the PCN-242 (Fe2Co) MOF beyond endotoxin detection, we explored its utility in glucose biosensing. Moreover, incorporating glucose oxidase (GOx) into the PCN-242 (Fe2Co) MOF framework further enhanced its peroxidase-like catalytic activity. This integration enabled sensitive glucose detection, achieving LODs of 4.24 μM for glucose and 2.2 μM for H2O2 within a linear range of 1 to 150 μM. The dual functionality of PCN-242 (Fe2Co) MOF as a peroxidase mimic and biosensor platform highlights its potential for advanced catalytic and diagnostic applications, offering a versatile and ethical alternative to conventional methods.

Treatment of textile wastewater using the Co(II)/NaHCO3/H2O2 oxidation system

Textile wastewater (TWW) is one of the most hazardous wastewaters for ecosystems when it is discharged directly into water streams without adequate treatment. Some organic pollutants, such as dyes in TWW, are considered refractory compounds that are difficult to degrade using conventional chemical and biological methods. The bicarbonate-activated peroxide (BAP) system is an advanced oxidation process (AOP) based on applying H2O2, which has been demonstrated to be a clean and efficient technology for dye degradation, with the advantage of operating under slightly alkaline pH conditions. In this study, response surface methodology (RSM) based on a central composite design (CCD) was used to optimize the degradation of TWW contaminated with the azo dye Acid Black 194 using the BAP system catalyzed with cobalt ions in solution (Co2+). The analysis of variance (ANOVA) technique was applied to identify significant variables and their individual and interactive effects on the degradation of TWW. The optimum reagent concentrations for degrading TWW at 25 °C and with 45 μM Co2+ were 787.61 and 183.34 mM for H2O2 and NaHCO3, respectively. Under these conditions, complete decolorization (≥99.40), 32.20 % mineralization, and 52.02 % chemical oxygen demand removal were achieved. Additionally, the acute toxicity of textile wastewater before and after oxidation was evaluated with guppy fish (Poecilia reticulata), showing a total reduction in mortality after treatment with the Co2+–BAP system. The Co2+–BAP oxidation system is a potential method for textile wastewater treatment, which, in addition to achieving complete decolorization and partial mineralization, improves biodegradability and reduces the toxicity of the treated water.

Dual-function sensor based on NH2-MIL-101(Fe)@Cu/CeO2 nanozyme for colorimetric and fluorescence detection of heavy metals

Heavy metal ions exhibit significant toxicity and pose threats to ecosystems and human health. Therefore, the development of sensitive detection methods is crucial. Nanozyme-based heavy metal sensors have garnered attention, yet existing nanozymes often suffer from low catalytic activity, limited functionality, and unclear mechanisms. To address these issues, this study successfully synthesized an organic-inorganic hybrid nanozyme (NH2-MIL-101(Fe)@Cu/CeO2) using doping and composite techniques, creating a dual-functional sensor. It's worth noting that in NH2-MIL-101(Fe)@Cu/CeO2, copper doping and heterojunction formation may increase oxygen vacancy concentration, promoting electron transfer. Compared to individual components like amino-terephthalic acid iron (III) metal-organic framework (NH2-MIL-101(Fe)) and copper-doped cerium dioxide (Cu/CeO2), this composite material exhibited enhanced peroxidase-like activity (oxidase-like, peroxidase-mimic, catalase-mimic, and superoxide dismutase-mimic). Particularly, NH2-MIL-101(Fe)@Cu/CeO2 displayed outstanding peroxidase-like activity, with Km values of 0.02 mM for TMB and 0.49 mM for H2O2, surpassing most nanozymes, along with high reaction rate (Vmax = 3.82 × 10−5 mM/s). Leveraging NH2-MIL-101(Fe)@Cu/CeO2's peroxidase-like behavior, TMB oxidation turned blue, inhibited by glutathione causing fading. Importantly, Hg2+ complexed with glutathione's thiol group forming GSH-Hg2+, restoring the blue color. Utilizing these properties, a colorimetric sensor for Hg2+ detection was developed. Furthermore, NH2-MIL-101(Fe)@Cu/CeO2 also exhibited remarkable fluorescence performance; Cu2+ binding with amino groups quenched fluorescence. Exploiting this phenomenon, a fluorescent sensor for Cu2+ detection was devised. Results demonstrated this dual-functional sensor's advantages: high sensitivity (LODHg2+ = 0.7 nM, LODCu2+ = 0.1 µM), strong selectivity, wide linear range (0.01 ∼ 4 µM and 8 ∼ 600 µM), and robust stability (90 % activity retained after three cycles).

Cu-MOF derived CuO@g-C3N4 nanozyme for cascade catalytic colorimetric sensing.

The use of peroxidase mimics has great potential for various real applications due to their strong catalytic activity. Herein, a facile strategy was proposed to directly prepare CuO@g-C3N4 by Cu-MOF derivatization and demonstrated its efficacy in constructing a multiple enzymatic cascade system by loading protein enzymes onto it. The resulting CuO@g-C3N4 possessed high peroxidase-like activity, with a Michaelis constant (Km) of 0.25 and 0.16mM for H2O2 and 3,3',5,5'-tetramethylbenzidine (TMB), respectively. Additionally, the high surface area of CuO@g-C3N4 facilitated the loading of protein enzymes and maintained their activity over an extended period, expanding the potential applications of CuO@g-C3N4. To test its feasibility, CuO@g-C3N4/protein oxidase complex was prepared and used to sense the ripeness and freshness of fruits and meat, respectively. The mechanism relied on the fact that the ripeness of fruits increasedand freshness of food decreased with the release of marked targets, such as glucose and xanthine, which could produce H2O2 when digested by the corresponding oxidase. The peroxidase mimics of CuO@g-C3N4 could then sensitively colorimetric detect H2O2 in present of TMB. The obtained CuO@g-C3N4/oxidase complex exhibited an excellent linear response to glucose or xanthine in the range of 1.0-120μmol/L or 8.0-350μmol/L, respectively. Furthermore, accurate quantification of glucose and xanthine in real samples is achieved with spiked recoveries ranging from 80.2% to 120.0% and from 94.2% to 112.0%, respectively. Overall, this work demonstrates the potential of CuO@g-C3N4 in various practical applications, such as food freshness detection.

PH-responsive dual-enzyme mimics based on hollow metal organic framework-derivatives β-Co(OH)2 for multiple colorimetric assays.

Ahollow metal organic framework derivative β-Co(OH)2has been prepared, which possesses oxidase and peroxidase-like activities. Oxidase-like activity is derived from the generation of free radicals, and peroxidase-like activity is related to the electron transfer process. Unlike other nanozymes with dual enzyme-like activities, β-Co(OH)2 possesses pH-responsive enzyme-like activities, among which the β-Co(OH)2 exhibits superior oxidase and peroxidase-like activities under pH of 4 and 6, respectively, which could avoid mutual interference between multiple enzymes. Based on the phenomenon that enzyme-like activities of β-Co(OH)2 can catalyze colorless TMB to generate blue oxidized TMB (oxTMB) with absorption peak at 652 nm, the sensors integrating total antioxidant capacity and H2O2 quantification were developed. The oxidase-like activity-based colorimetric system has a sensitive response to ascorbic acid, Trolox, and gallic acid, in which the limit of detection for those antioxidant substances was 0.54 μM, 1.26 μM, and 14.34 μM, respectively. The sensors based on peroxidase-like activity hadlow limit of detection of 1.42 μM for H2O2 and alinear range of 5-1000 μM. Theproposed method can be well applied to the detection of the total antioxidant capacity of kiwi, Vc tables, orange and tea extract with high accuracy, and H2O2 determination in milk and glucose detection in beverages with satisfactory recovery (within 97-106%).

Conductive nano-gold self-assembled MXene@hemin with high catalytic activity achieved by strong metal-support interactions: A powerful nanozyme for development of electrochemical aptasensor in tuberculosis diagnosis

Despite multiple advances in tuberculosis (TB), there is still a lack of effective methods available for its diagnosis. To this end, we developed a novel nanozyme-mediated electrochemical aptasensor for TB diagnosis. We showed that hemin decorated with multi-layered MXene enhanced the metal-support interaction with nano-gold via charge transfer, resulting in excellent peroxidase-like activity aside from the highly conductive feature. TheKmvalue of hemin functionalized MXene decorated with nano-gold (MXene@hemin-Au) was 0.37 mM and 0.23 mM for H2O2 and TMB, respectively, which was smaller to that of MXene@hemin (4.01 mM and 0.39 mM) or horseradish peroxidase (3.7 mM and 0.434 mM), indicating its high affinity to both substrates, showing improved stability in harsh conditions and excellent biocompatibility. Given these advantages, an ultrasensitive detection method was established based on a typical sandwich format using a combination of specific Mycobacterium tuberculosis (MTB) ESAT-6 antigen aptamers with MXene@hemin-Au as probes for signal amplification and gold nanoparticles supported nitrogen-doped carbon nanotube (N-CNTs-Au) as a sensing platform. It exhibited a wide detection linear for ESAT-6 antigen from 100 fg mL−1to 50 ng mL−1, with limit of detection and limit of quantification of 2.36 fg mL−1 and 7.87 fg mL−1, respectively. For its diagnostic application, of note, the proposed method outperformed diagnostic performance for TB in contract to a commercial ELISA method in terms of specificity (100% vs. 20.59%) and area under curve (0.987 vs. 0.596), verifying its great potential in clinical practice.

A Multiple-Responsive Fluorescence Probe Based on Water-Soluble Fluorescent Conjugated Polymer for Biomolecules Detection

In this paper, we designed a multiresponsive fluorescent probe based on a synthetic water-soluble conjugated fluorescent polymer (PF-DBT-S-S-PDI) consisting of the conjugated fluorescent backbones and the hydrophilic side chains connected by a disulfide bond. Based on its specific structures, according to two different response mechanisms of fluorescence resonance energy transfer (FRET) and heavy atom effect, the polymer shows high sensitivity and selectivity toward reductive species-thiols and oxidizing substances (such as H2O2) in different ways. Owing to the presence of disulfide bonds, the reductive mercaptan in the solution would cause the water-soluble branches in the micellar structure to break off and leave, which causes the hydrophobic framework of the polymer to aggregate and enhance the fluorescence intensity. On the other hand, because the PDIs in branches are ionic polymers with many iodide ions, H2O2 in solution oxidizes iodide ions into iodide so that the heavy atomic effect of iodide would quench the fluorescence. Both mechanisms have high sensitivity; e.g., the detection limits for mercaptan (such as cysteine) were 0.052 mM, 5.26 μM for H2O2, and 1.06 μM for glucose (combined with oxidase). The multiple detection ability of the polymer has been validated by evaluating free thiols and glucose levels in food samples and tissue homogenates. Our work provided a strategy for integrating multiple species detection capabilities on a single probe.

An electrochemical determination strategy for miRNA based on bimetallic nanozyme and toehold-mediated DNA replacement procedure.

An electrochemical strategy based on bimetallic nanozyme in collaboration with toehold-mediated DNA replacement effect is proposed for the sensitive determination of miRNA-21. The AuPt nanoparticles (AuPt NPs) are prepared as a catalytic beacon; it shows favorable peroxidase properties with a Michaelis contant (Km) of 0.072mM for H2O2, which is capable of catalyzing H2O2 to induce an intense redox reaction, and causing a measurable electrochemical signal. To further enhance the strength of the signal response, a novel toehold-mediated DNA replacement strategy is employed. DNA strands with specific sequences are modified on electrodes and AuPt NPs, respectively. In the presence of miRNA-21, a cyclic substitution effect is subsequently activated via a specific toehold sequence and leads to a large accumulation of AuPt NPs on the electrodes. Subsequently, a strong signal depending on the amount of miRNA-21 is obtained after adding a small amount of H2O2. The analytical range of this determination method is from 0.1pM to 1.0nM, and the LOD is 84.1 fM. The spike recoveries for serum samples are 95.0 to 102.4% and the RSD values are 3.7 to 5.8%. The results suggests a promising application of the established method in clinical testing and disease diagnosis.

High-performance enzyme-free glucose and hydrogen peroxide sensors based on bimetallic AuCu nanoparticles coupled with multi-walled carbon nanotubes

Interest in designing and manufacturing non-enzymatic biosensors is growing which stimulates the increased research efforts to explore innovative nanocomposites with highly catalytic activity. Here, the development of high-performance non-enzymatic glucose and hydrogen peroxide (H2O2) sensors based on bimetallic AuCu nanoparticles coupled with multi-walled carbon nanotubes (AuCu@MWCNTs) was achieved in this work. They were investigated by the cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) methods separately. Benefiting from the synergistic effects of AuCu@MWCNTs, the proposed biosensors exhibited excellent performance such as low detection limits (1.3 nM for glucose, 0.1 nM for H2O2), broad linear ranges (8 nM-60 mM for glucose, 1 nM-4 mM for H2O2) and high sensitivities (362.3 μA·mM−1·cm−2 for glucose, 1335 μA·mM−1·cm−2 for H2O2). Besides, the AuCu@MWCNTs based electrodes provided excellent stability, repeatability and reproducibility. Based on the outstanding performance, they exhibited good reliability and accuracy in the detection of glucose in goat serum samples and real-time monitoring of H2O2 released by living cells. The present work suggests that the fabricated biosensor holds great potential for non-enzymatic glucose determination and real-time quantitative detection of H2O2 in biomedical applications.

Low-density Pt nanoarray-based hydrogen peroxide sensing platform and its application in trace sarcosine detection

Hydrogen peroxide (H2O2) is an important signaling molecule that regulates many biological processes. It is of great value to realize rapid, accurate, highly sensitive and low-cost H2O2 detection in the immediate detection of trace disease markers. Low-density nanoelectrode arrays have a high signal-to-noise ratio and are advantageous for trace detection. In this paper, low-density Pt nanoelectrode arrays were successfully prepared by a simple method of ion sputtering combined with electrodeposition based on a track-etched polycarbonate membrane template. The arrays had a detection limit as low as 0.03 μM for H2O2 at a constant potential, a sensitivity of 125.9 μA mM−1, and a linear range spanning nearly four orders of magnitude (0.1–655 μM). The developed sarcosine sensors based on these arrays had a very low detection limit (0.08 μM) and wide linear range (0.5–64.5 μM) for the rapid detection of trace amounts of sarcosine in serum. With a wide linear range and low detection limits, this hydrogen peroxide sensing platform has great potential for use in the rapid electrochemical detection of trace substances.

Interfacial Regulation of ZIF-67 on Bacteria to Generate Bifunctional Sensing Material on Chip for Qualifying Cell-Released Reactive Oxygen Species.

Cell's activities are highly dependent on signal molecules, of which reactive oxygen species of the superoxide anion (O2•-) and hydrogen peroxide (H2O2) are important ones that always work together to regulate biological processes such as apoptosis and oxidative stress. It is of significance to realize simultaneous qualification of O2•- and H2O2 but it still faces challenges particularly in live-cell assay with a complex environment. We report the design of a bifunctional sensing material by interfacially regulating ZIF-67 on bacteria Shewanella putrefaciens to generate cobalt nanoparticles/nitrogen-doped porous carbon nanorods (Co/N-doped CNRs) and its sensing chip for qualifying cell-released O2•- and H2O2. Co/N-doped CNRs exhibit unique properties including porous structure for significantly increased reaction surface area and coordinating Co nanoparticles for rich active sites. The bifunctional Co/N-doped CNRs is used to fabricate the electrochemical sensing chip, which achieves a fast response time (0.5 s for O2•-, 1.9 s for H2O2), a low detection limit (0.69 nM for O2•-, 2.25 μM for H2O2), and a remarkably high sensitivity (792.30 μA·μM-1·cm-2 for O2•-, 153.91 μA·mM-1·cm-2 for H2O2), among the best of reported bifunctional nanozymes.

Proton-Conductive and Electrochemical-Sensitive Sensing Behavior of a New Mn(II) Chain Coordination Polymer

In this work, a novel Mn(II) chain coordination polymer (Mn-CP), {[Mn(iip)(2bbpum)0.5(H2O)3]·2H2O}n [H2iip = 5-iodoisophthalic acid, 2bbpum = N,N′-bis(2-pyridinemethyl)oxamide] was synthesized under ambient conditions. Mn-CP further assembles into a 3D supramolecular architecture through hydrogen bonds, halogen bonds, and ππ stacking interactions. The composite Mn-CP/nafion membrane has low activation energy for proton transfer, which results in its temperature-insensitive proton conductivity. The cyclic voltammetry demonstrates that the Mn-CP electrode (Mn-CP/GCE) shows quite different redox properties in 0.1 M H2SO4 and 0.1 M PBS aqueous solutions. The Mn-CP/GCE exhibits a couple of irreversible redox peaks with an oxidation peak potential suitable for the nitrite oxidation in 0.1 M H2SO4. Quite differently, in the PBS aqueous buffer solution, the Mn-CP electrode has a couple of irreversible redox peaks. The reduction peak potential is appropriate for the H2O2 reduction. So, the Mn-CP/GCE can be used not only in the electrocatalytic oxidation of NO2– but also in the electrocatalytic reduction of H2O2. The amperometric response reveals that the Mn-CP/GCE exhibits high-selective and extremely sensitive oxidation sensing of NO2– and reduction sensing of H2O2. The exponential detection range is 0.01–20 mM for NO2– and 0.01–10.5 mM for H2O2. The linear detection range for both H2O2 and NO2– is 0.01–0.10 mM. The detection limit is 1.865 μM for NO2– and 8.57 μM for H2O2. The Mn-CP/GCE exhibits high electrochemical stability and fine reproducibility. Moreover, the strategy can be translated to a portable screen-printed electrode (SPE). The Mn-CP/SPE shows more sensitive sensing to NO2– and H2O2 than Mn-CP/GCE. Moreover, it can detect NO2– and H2O2 efficiently in the real-world samples. So, Mn-CP may be a potential dual nonenzymatic electrochemical sensory material for NO2–via oxidation sensing and H2O2via reduction sensing.