Sensitive Detection Of H2O2 Research Articles

Manganese Sulfanyl Porphyrazine-MWCNT Nanohybrid Electrode Material as a Catalyst for H2O2 and Glucose Biosensors.

The demetallation reaction of sulfanyl magnesium(II) porphyrazine with N-ethylphthalimide substituents, followed by remetallation with manganese(II) salts, yields the corresponding manganese(III) derivative (Pz3) with high efficiency. This novel manganese(III) sulfanyl porphyrazine was characterized by HPLC and analyzed using UV-Vis, MS, and FT-IR spectroscopy. Electrochemical experiments of Pz3 conducted in dichloromethane revealed electrochemical activity of the new complex due to both manganese and N-ethylphthalimide substituents redox transitions. Subsequently, Pz3 was deposited on multiwalled carbon nanotubes (MWCNTs), and this hybrid material was then applied to glassy carbon electrodes (GC). The resulting hybrid electroactive electrode material, combining manganese(III) porphyrazine with MWCNTs, showed a significant decrease in overpotential of H2O2 oxidation compared to bare GC or GC electrodes modified with only carbon nanotubes (GC/MWCNTs). This improvement, attributed to the electrocatalytic performance of Mn3+, enabled linear response and sensitive detection of H2O2 at neutral pH. Furthermore, a glucose oxidase (GOx)-containing biosensing platform was developed by modifying the prepared GC/MWCNT/Pz3 electrode for the electrochemical detection of glucose. The bioelectrode incorporating the newly designed Pz3 exhibited good activity in the presence of glucose, confirming effective electronic communication between the Pz3, GOx and MWCNT surface. The linear range for glucose detection was 0.2-3.7 mM.

A non-enzymatic hydrogen peroxide biosensor based on cerium metal-organic frameworks, hemin, and graphene oxide composite

This study presents the development of a novel non-enzymatic electrochemical biosensor for the real-time detection of hydrogen peroxide (H2O2) based on a composite of cerium metal–organic frameworks (Ce-MOFs), hemin, and graphene oxide (GO). The Ce-MOFs served as an efficient matrix for hemin encapsulation, while GO enhanced the conductivity of the composite. Characterization techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, UV–vis spectroscopy, and thermogravimetric analysis (TGA) confirmed the successful integration of hemin into the Ce-MOFs. The Ce-MOFs@hemin/GO-modified sensor demonstrated sensitive H2O2 detection due to the exceptional electrocatalytic activity of Ce-MOFs@hemin and the high conductivity of GO. This biosensor exhibited a linear response to H2O2 concentrations from 0.05 to 10 mM with a limit of detection (LOD) of 9.3 μM. The capability of the biosensor to detect H2O2 released from human prostate carcinoma cells was demonstrated, highlighting its potential for real-time monitoring of cellular oxidative stress in complex biological environments. To further assess its practical applicability, the sensor was tested in human serum samples, yielding promising results with recovery values ranging from 94.50 % to 103.29 %. In addition, the sensor showed excellent selectivity against common interfering compounds due to the outstanding peroxidase-like activity of the composite.

Probing trace of intracellularly-originated hydrogen peroxide based Pt–Cd bimetallic nanozyme on an enzyme-free electrochemical sensor

BackgroundMeasurement of endogenous cellular hydrogen peroxide (H2O2) can provide information on cellular status, and help to understand cellular metabolism and signaling processes, thus contributing to elucidation of disease mechanisms and new diagnostics/therapeutic approaches. ResultsIn this work, Pt–Cd bimetallic nanozyme was successfully prepared via the solvothermal synthetic method for sensitive detection of H2O2. The synthesized Pt–Cd bimetallic nanozyme could exhibited good electrochemical activity. Then, the materials were analyzed for the electrochemical properties and catalytic properties of H2O2 by cyclic voltammetry and chronoamperometry, respectively. Results indicated that the synthesized nanozyme had superior sensitivity (295 μA⸳mM−1⸳cm−2) and selectivity toward H2O2 with a detection limit of 0.21 μM. Further, the Pt–Cd bimetallic nanozyme displayed good electrochemical properties compared to platinum catalysts alone. The application was extended to determine the produced H2O2 from human hepatocellular carcinoma cells (HepG2) and normal hepatocyte (LO2) samples after ascorbic acid stimulation, thus enabling the early warning of cellular carcinogenesis. SignificanceThis strategy promises simple, rapid, inexpensive and effective electrochemical sensing and provides a new pathway for the synthesis of bimetallic nanozymes to construct an electrochemical sensor for the sensitive detection of H2O2.

AI‐Assisted Plasmonic Enhanced Colorimetric Fluidic Device for Hydrogen Peroxide Detection from Cancer Cells

AbstractHydrogen peroxide (H2O2) is an essential molecule to various physiological processes and is commonly used for the detection and monitoring of glucose and cell viability. Furthermore, it is identified as a signal of oncogenic growth due to its widespread presence within the cancer cell environment. However, the low concentrations of H2O2 released by cancer cells' metabolism challenge current detection methods' capabilities and their practicality for translation to clinical applications. Colorimetric assays with simple readouts are a promising solution, provided that their sensitivity and rapidity in detecting H2O2 improve. Here, a plasmonic enhanced nanopatterned platform is proposed coupled with an Amplex Red assay to monitor the color change of H2O2 released from cancer cells. The nanopatterned platform embedded into a multiplexed microfluidic device enhances the kinetics of the reaction ≈7 times. This approach has reached a limit of detection of 1 pm when tested in breast (MCF‐7) and prostate (PC‐3) cancer media. The collected color images are processed and analyzed by a machine learning algorithm that categorizes them into “high” or “low‐to‐no” concentrations of H2O2 with 91% accuracy. This study is a step toward developing a device for highly sensitive H2O2 detection that is easily adaptable, user‐friendly, portable, and automated.

New cosolvent-dependent electrochemical sensing behavior of a pair of isostructural ionic nickel(II) coordination polymers

A pair of isostructural ionic nickel(II) chain coordination polymers, {[Ni(bbbm)(H2O)4]·ATBIP·2DMF·2H2O}n (CP 1) and {[Ni(bbbm)(H2O)4]·ATBIP·2DMA·2H2O}n (CP 2) with the multi-functional ATBIP2- anion and flexible bbbm linker was synthesized under ambient condition [H2ATBIP = 5-amino-2,4,6-tribromoisophthalic acid, bbbm = 1,4-bis(benzimidazole-1-methyl)benzene]. Furthermore, the composite of CP 1 with carbon nanotubes (CP 1@CNTs) was constructed by adopting “one pot” synthesis strategy. With the help of the hydrogen-bonded chain, CPs 1–2 extend into a 3D supramolecular framework with 1D channels occupied by the cosolvent molecules (DMF/DMA). Remarkably, CPs 1–2/GCE demonstrate cosolvent-dependent electrochemical sensing behavior to H2O2 and Fe3+. CP 1/GCE shows more sensitive oxidation sensing to H2O2 than CP 2/GCE in 0.1 M NaOH. Meanwhile, CP 1/GCE demonstrates sensitive reduction sensing to Fe3+ in 0.1 M H2SO4, while CP 2/GCE doesn't. Both CPs 1–2/GCE have similar oxidation sensing capabilities to ascorbic acid (AA) in 0.1 M H2SO4. Moreover, CP 1@CNTs/GCE shows superior electrochemical sensing performance to CP 1/GCE. The LOD of CP 1@CNTs/GCE for sensing of H2O2, AA and Fe3+ reaches 0.1 μM, 1.7 μM and 3.4 μM, respectively. Moreover, CP 1@CNTs/GCE was used in the sensitive detection of H2O2, AA and Fe3+ in the real-world samples.

Bimetallic MOF-derived three-dimensional nanoflowers PdCoOx as peroxidase mimic activity for determining total antioxidant capacity

Bimetallic MOF derivatives have shown excellent performance as nano-enzymes in the field of catalysis. Herein, PdCo oxide nanoflowers with three-dimensional flower were prepared by a simple pyrolysis method on a precursor of bimetallic PdCo-MOF. PdCoOx showed excellent peroxidase mimic activity, which could significantly promote the oxidation of TMB by H2O2. Compared with CoOx, the peroxidase mimic activity of the optimized PdCoOx-300 increased by 2.41-fold. PdCoOx-300 has high affinity for TMB and H2O2 with Km values of 0.16 mM and 2.11 mM, which are only 57.03% and 36.87% of HRP, respectively. The highly specific peroxidase mimic activity is conducive to the sensitive detection of H2O2, glucose and ascorbic acid with limit of detection of 10, 100 and 10 nM, respectively. Furthermore, the total antioxidant capacity in the actual beverage samples was conducted, which showed good anti-interference ability and recovery rate.

A biocompatible chitosan-based fluorescent polymer for efficient H2O2 detection in living cells and water samples

As a biomarker of oxidative stress, hydrogen peroxide (H2O2) plays a complex role in organisms, including regulating cell signaling, respiration, the immune system, and other life processes. Therefore, it is important to develop a tool that can simply and effectively monitor H2O2 levels in organisms and the environment. In this work, naphthalene fluorophores with a borate structure were introduced into chitosan (CTS) azide, and a CTS-based fluorescence sensor (CTS-HP) was designed for sensitive H2O2 detection. The biocompatibility and degradability of CTS endowed CTS-HP with reduced biotoxicity compared with organic fluorescent dyes, and the substitution degree of fluorophores on the CTS chains was 0.703. The randomly coiled chain structure of the CTS-HP probe enabled the boronic acid recognition sites on the fluorophores to achieve the enrichment of analyte H2O2 through a synergistic effect. Therefore, the probe CTS-HP (10 μg mL−1) exhibited a 21-fold fluorescence enhancement and good detection limit (LOD = 8.98 nM) in H2O2 solution, reaching the maximum fluorescence response faster (within 16 min). The probe also successfully achieved the fluorescence imaging of endogenous and exogenous H2O2 in zebrafish and living cells and labeled the recovery experiment of H2O2 in real water samples (recoveries rates of 90.93–102.9 % and RSD < 3.09 %).

Engineered Fe3O4 nanoreactor as a high-performance hydrogen peroxide sensor

Nanozymes with peroxidase-mimicking activities have been extensively explored for hydrogen peroxide (H2O2) detection. However, the conventional nanozyme assay with suspensions suffer the limitations of restricted available surface, loss of short-lived radicals, and slow reaction in non-acidic conditions, thus have a greatly reduced detection sensitivity. We here proposed to overcome these drawbacks by constructing aligned nanoreactor sensor with Fe3O4 nanozymes distributed alongside the nanochannels of anodized aluminum oxide (termed as NR-Fe3O4), which allowed for a spatially confined nanozyme reactions (ca. 5 nm) operated under a filtration reaction mode. We presented the unique merits of NR-Fe3O4 on H2O2 detection compared to Fe3O4 nanozyme suspensions, together with the mechanism discussion about how the radical production and capturing got maximized under the confinement. As a result, our NR-Fe3O4 sensor featured a highly sensitive H2O2 detection with a linear concentration from 10 to 5000 nM (detection limit of 0.9 nM), expanded workable pH to neutral, and enhanced nanozyme stability for at least 8 h continuous run. We further showed the great feasibility of using NR-Fe3O4 sensor in complex water matrices for H2O2 detection, as it allowed for a pore rejection of background organics which in turn protected the internal radicals for a capturing and signal magnification. Our findings highlight the great interest of constructing confinement nanoreactors as an innovative approach of enhancing H2O2 detection sensitivity based on the nanozyme assay.

Versatile electrode platform for determination of hydrogen peroxide in serum samples based on hemoglobin embedded in iron oxide/reduced graphene oxide nanocomposite

Hydrogen peroxide (H2O2) is a vital messenger molecule facilitating signal transmission within cellular systems. The accurate quantification of H2O2 in complex environments, such as human serum, is instrumental in elucidating its diverse biological functions. In this study, we present the development of a robust electrode platform by integrating hemoglobin onto iron oxide (Fe3O4) nanoparticles and reduced graphene oxide (rGO) as a conducting support for the sensitive detection of H2O2 in human serum. The Fe3O4/rGO nanocomposite was synthesized via a facile single-step thermolysis reaction in the presence of oleylamine. Transmission electron microscopy (TEM) analysis revealed the formation of highly monodisperse Fe3O4 nanoparticles that were uniformly dispersed over the reduced graphene surface. The rGO surface provided abundant active sites (Fe3O4) for H2O2 sensing. Consequently, the resulting Hb/Fe3O4@rGO modified electrode exhibited a wide linear range of H2O2 concentrations from 1.5 to 2684 µM, demonstrating high sensitivity and low detection limit. Further characterization of the Hb/Fe3O4@rGO/GC electrode revealed a high surface coverage (τ = 3.0 × 10−9 mol cm−2), charge transfer coefficient (α = 0.83), and electron transfer rate constant (ks = 1.33 s−1). Subsequently, the Hb/Fe3O4@rGO/GC sensor probe was employed to analyze H2O2 in real human serum samples, demonstrating excellent recovery rates ranging from 99.8 % to 104.0 %. The nanocomposite material, designed through the innovative combination of graphene oxide reduction, Fe3O4 nanoparticle decoration, and oleylamine amide/amine bonding, serves as an excellent electrode material for H2O2 concentration sensing. Thus, this study presents a promising platform for the future determination of H2O2 biomarkers in clinical settings.

Electrochemically enhanced peroxidase-like activity of nanohybrids for rapid and sensitive detection of H2O2 and Dopamine

Longer detection times and low sensitivities are the two main drawbacks of applying colorimetric detection methods in field applications where rapid and sensitive detection is required. A discovery of the enhancement of nanozymatic activity via electrochemical means which significantly reduces the analyte detection time and enables ultra-low detection levels has been reported in this paper. A novel, simple and facile approach for the synthesis of carbon quantum dot-gold nanoparticles (CQD-AuNPs) has been developed. The CQD-AuNPs showcased catalytic activity through the oxidation of 3,3′,5,5′-Tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2) and followed the characteristic Michaelis-Menten equation. Surprisingly, the catalytic activity of CQD-AuNPs nanohybrids enhanced considerably while the reaction was completed under an electrochemical process and assisted the detection of H2O2 and Dopamine (DA) with a limit of detection (LOD) value of 240 nM, and 0.75 μM, respectively. Most importantly, the detection time decreased by 60-fold compared to conventional nanozymatic reactions. The work covered in this paper provides a novel approach to develop the nanocomposite and a new detection technique that can be utilized across various fields of science and engineering to improve and exploit enzymatically dependent reactions.

An electrochemical sensor based on FeCo bimetallic single-atom nanozyme for sensitive detection of H2O2

Efficient catalytic decomposition of H2O2 is accompanied by electron transfer through Fe-Nx active sites of hemin in the human body. Inspired by this reaction process, the Fe SAs/Co CNs were successfully synthesized by combined Co atomic sites with nitrogen-carbon doped Fe single-atom active sites (SAs). The synergy between transition metals not only reduces agglomeration during synthesis but also improves its own electrical conductivity due to the interaction between Fe and Co that promotes the formation of graphite surface. Crucially, the synergistic effect of the Co site significantly enhanced the peroxidase activity of the Fe SAs and the reaction rate of the Fenton-like reaction, resulting in an efficient detection of H2O2. Catalytic kinetic calculations and enzymatic kinetic calculations were used to verify the electron transfer rate and catalytic performance of their constructed electrochemical sensing interfaces. The results showed that Fe SAs/Co CNs@GCE showed better detection performance than Fe SAs CNs@GCE. It was applied successfully to detect H2O2 released from cells in real-time as well. The linear detection range of Fe SAs/Co CNs@GCE for H2O2 was 1–16664 μM, and the detection limit was as low as 0.25 μM. Furthermore, an electrochemical sensing chip was constructed using Fe SAs/Co CNs@SPE and the prepared microfluidic channel. The constructed portable FeSAs/Co CNs@SPE had a linear range of 1–400 μM and a detection limit of 0.36 μM and achieved the recovery detection of H2O2 in serum. The electrochemical sensing interfaces constructed based on Fe SAs/Co CNs all have efficient catalytic performance and excellent real-time hydrogen peroxide detection performance, which have practical application potential for human oxidative stress level detection. And it provides a novel approach to the trace detection of bioactive small molecules.

FeTOMPP with Peroxidase-Like Activity as Peroxidase Mimics for Colorimetric Sensing of H2O2 and Ethanol

In this study, FeTOMPP (Tetrakis(4-methoxyphenyl) phenylporphyrinatoiron(III)) was synthesized and investigated for its peroxidase-like activity. The catalytic performance of FeTOMPP as a peroxidase mimic was explored by utilizing the colorless peroxidase substrate, 3,3',5,5'-tetramethylbenzidine (TMB), in the presence of hydrogen peroxide (H2O2). The oxidation of TMB by FeTOMPP resulted in the formation of its blue oxidized state. This enzymatic reaction was employed for the quantitative detection of H2O2, with a linear detection range spanning from 1.0 to 100 µM. The detection limit achieved using FeTOMPP as the catalyst was determined to be 2.4 µM. Furthermore, kinetic studies were conducted to investigate the interaction between FeTOMPP and H2O2. The results indicated that FeTOMPP exhibited favorable affinity towards H2O2, further highlighting its potential as a peroxidase mimic. In addition to its peroxidase-like activity, a simple and sensitive visual and colorimetric method was developed for the detection of ethanol by combining FeTOMPP with alcohol oxidase. The method relied on the use of TMB as the substrate. Ethanol-containing samples were subjected to the enzymatic reaction, resulting in the generation of a color change. The detection of ethanol was achieved with a minimum detection limit of 0.95 % v/v, and the linear range for quantification extended from 0 to 15 % v/v. This study demonstrates the potential application of FeTOMPP as a peroxidase mimic for the sensitive detection of H2O2 and the development of a colorimetric method for ethanol detection. The findings highlight the versatility and promising capabilities of FeTOMPP in various analytical and diagnostic applications. HIGHLIGHTS The potential application of FeTOMPP as a peroxidase mimic for the sensitive detection of H2O2. The development of colorimetric method for ethanol detection by combining FeTOMPP with alcohol oxidase. GRAPHICAL ABSTRACT

Sensitive and cost-effective colorimetric sensor based on enzyme mimic MoS2@CoTiO3 nanocomposite for detection of hydrogen peroxide in milk and tap water

Although hydrogen peroxide (H2O2) is essential for biochemical reactions and industrial processes but excessive levels can be hazardous to health. As a result, developing a reliable, selective, and sensitive H2O2 detection method remains challenging. This study proposes an inexpensive, portable, and rapid colorimetric sensor for quick H2O2 detection based on a filter paper-based platform and novel nanozymes named Molybdenum disulfide and Cobalt titanate (MoS2@CoTiO3) nanocomposite.Different analytical techniques were used to evaluate the interaction between the material and analyte, including UV-Visible spectrophotometry, Fourier transform infrared spectroscopy, Scanning electron microscopy, X-Ray diffraction, Zeta potential, and Dynamic light scattering. The characterization study proved the proposed material's appropriateness for sensing purposes. The combined action of MoS2 and CoTiO3 components revealed intrinsic peroxidase-like activity, allowing for the visible oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB). Several optimization parameters were evaluated, including TMB concentration (25 mM), incubation time (20 min), pH (7.0), and nanocomposite (3.0 mg) and gel (0.2 g) concentrations. Consequently, due to its peroxidase-like activity, the MoS2@CoTiO3 nanocomposite achieved a lower detection limit (LOD) of 0.01 µM. The platform displayed adequate selectivity against potential interferants in biological samples, with excellent recovery rates ranging from 93.3 % to 98.3 %. The use of low-cost paper-based porous substrates for sensing has proven to be a versatile option for onsite health and environmental monitoring, providing an alternative to costly and complicated instrumentation.

Green reduction and uniform assembly of silver nanoparticles on polydopamine functionalized sulfur-doped graphitic carbon nitride nanosheets for highly sensitive H2O2 detection via nonenzymatic approach

In this study, we demonstrate a new strategy to fabricate an enzyme-free hydrogen peroxide (H2O2) sensor electrode based on silver nanoparticles (AgNPs) decorated polydopamine/sulfur-doped graphitic carbon nanocomposite (denoted as AgNPs@PDA/S-g-C3N4). The S-g-C3N4 nanosheets are derived from the pyrolysis of trithiocyanouric acid, followed by thermal exfoliation. A mussel-inspired PDA nanolayer enhances the solubility and high dispersion of S-g-C3N4 nanosheets and AgNPs in aqueous phase synthesis. The amine and catecholic functional groups of PDA are the major nucleation sites for Ag+ ions adsorption and ascorbic acid was further used as a green reducing agent for the growth of AgNPs. PDA adhesion layer can effectively connect the AgNPs and S-g-C3N4 nanosheets via electrostatic interaction to increase the stability and biocompatibility of the ternary composite structure. Various spectroscopy and microscopy techniques confirmed the formation of AgNPs@PDA/S-g-C3N4 nanocomposite. Our AgNPs@PDA/S-g-C3N4 nanocomposite fabricated disposable sensor exhibited outstanding sensing ability to H2O2 reduction at −0.65 V (vs. Ag/AgCl), which is confirmed through an amperometric detection method. The sensor exhibits rapid response (2 s) to H2O2 sensing with high sensitivity (1020 μA mM−1 cm−2), wide detection range (0.002–23 mM) and low limit of detection of 0.086 μM. The practicality of the H2O2 sensor was evaluated with commercial milk and mouthwash samples, which retained satisfactory recoveries. Thus, our results indicate that the PDA functionalization not only enhances the S-g-C3N4 solubility but also increases the interfacial charge transport in AgNPs@PDA/S-g-C3N4 nanocomposite material which develops a potential sensing method for nonenzymatic H2O2 sensor. Due to the effective surface modification strategies, such as PDA nanocoating and AgNPs deposition, the exfoliated S-g-C3N4 nanosheets gained excellent electrochemical properties, facilitating potential candidates in electrochemical applications.

Restricted intramolecular vibrations assisted enhanced fluorescence emission response of probe: A new experimental and theoretical approach for the detection of hydrogen peroxide

Hydrogen peroxide (H2O2) is a harmful chemical used as a signature compound in forming easily synthesizable peroxide-based explosives. Therefore, detecting H2O2 vapors and solutions is imperative to avoid terroristic activities. Aggregation induced emission enhancement (AIEE) active probe PATdetected H2O2 based on geometry-dependent hydrogen bonding. Unlike frequently reported fluorescent probes, probePATexhibited a strong fluorescence emission enhancement response for H2O2 due to restrictions in intramolecular vibrations of probe. This unique sensing phenomenon enhances our probe's versatility and potential applications in the selective and sensitive detection of H2O2. 1H NMR titration experiments and extensive density functional theory (DFT) calculations explained the distinct sensing mechanism. As a result of efficient interaction, probe could detect H2O2 with critical features of excellent selectivity, nanoscale level detection (LOD; 10 nM), fast response (20 sec.), and distinguished photostability. Conveniently, probePAT-embedded fluorescent strips were successfully employed as a portable sensing tool for rapidly recognizing H2O2 vapors. Moreover, probePATwas also capable of H2O2 determination in industrial water, orange juice, milk samples and commercially available products. Therefore, our probe holds promising features for trace detection of H2O2 in vapor and solution phase that make it highly useful.

Protein Nanotubes Assembled from Imidazole-Grafted Horseradish Peroxidase Nanogels.

Protein assembly, a common phenomenon in nature, plays an important role in the evolution of life. Inspired by nature, assembling protein monomers into delicate nanostructures has emerged as an attractive research area. However, sophisticated protein assemblies usually need complicated designs or templates. In this work, we successfully fabricated protein nanotubes in a facile way by coordination interactions between imidazole-grafted horseradish peroxidase (HRP) nanogels (iHNs) and Cu2+. The iHNs were synthesized by polymerization on the surface of HRP by employing vinyl imidazole as a comonomer. By direct addition of Cu2+ into iHN solution, protein tubes were therefore formed. The size of the protein tubes could be adjusted by changing the added Cu2+ amount, and the mechanism behind the formation of protein nanotubes was elucidated. Furthermore, a highly sensitive H2O2 detection system was established based on the protein tubes. This work provides a facile method to construct diverse sophisticated functional protein nanomaterials.

Enhancing catalytic performance of Fe and Mo co-doped dual single-atom catalysts with dual-enzyme activities for sensitive detection of hydrogen peroxide and uric acid

Single-atom catalysts (SACs) have attracted much attention due to their excellent catalytic activity, but the improvement of atomic loading which means that weight fraction (wt%) of metal atom was still facing great challenges. In this work, iron and molybdenum co-doped dual single-atom catalysts (Fe/Mo DSACs) was prepared for the first time by using the soft template sacrifice strategy, which improved significantly the atomic load and exhibited both the oxidase-like (OXD) activity and the dominant peroxidase-like (POD) activity. Further experiments reveal that Fe/Mo DSACs can not only catalyze O2 to generate O2•− and 1O2, but also catalyze H2O2 to generate a large number of •OH, which caused 3, 3′, 5, 5′-tetramethylbenzidine (TMB) to be oxidized to oxTMB, accompanied by the color changing from colorless to blue. The steady-state kinetic test showed that Michaelis–Menten constant (Km) values and the maximum initial velocity values (Vmax) of the POD activity of Fe/Mo DSACs were 0.0018 mM and 12.6 × 10−8 M s−1, respectively. The corresponding catalytic efficiency was tens of times higher than Fe SACs and Mo SACs, which proves that the synergistic effect between Fe and Mo has significantly improved the catalytic ability. Based on the excellent POD activity of Fe/Mo DSACs, a colorimetric sensing platform combined with TMB was proposed to realize the sensitive detection of H2O2 and uric acid (UA) in a wide range, with limits of detection as low as 0.13 and 0.18 μM, respectively. Finally, accurate and reliable results were obtained in the detection of H2O2 in cells, and of UA in human serum and urine.

One-pot electrodeposition of multilayered 3D PtNi/polymer nanocomposite. H2O2 determination in aerosol phase

In this work, 3D-structured nanocomposites were synthesized in one pot by electrochemical deposition of alternating layers of an azo type polymer (polyazure-A) with platinum and nickel nanoparticles. The hybrid PtNi/poly(AzA) film was electrochemically deposited on screen-printed carbon electrodes by layer-by-layer assembly as a function of the number of cyclic voltammograms for electrodeposition of the conducting polymer and the electrode potential applied for electro-reduction of the metal salts. The physicochemical characteristics of the resulting films were studied using electrochemical and microscopic techniques. The 3D molecular nanoarchitecture presents a hollow porous structure dependent on the electrode potential set for the electro-reduction of Pt and Ni nanoparticles. The electrochemical sensor was validated in terms of sensitivity, limit of detection, stability and repeatability, exhibiting a highly sensitive H2O2 detection, with LoD 68.5 nM (S/N = 3) at 0.05 V vs. Ag-SPCE for the electrode modified with 20 cycles for the conducting polymer electrodeposition and −2.0 V for metal ions reduction. The aim of this work also included the outcome of the electrochemical sensor after incorporating the room temperature ionic liquid 1‑butyl‑2,3-dimethylimidazolium tetrafluoroborate within the PtNi/poly(AzA) film, which notably improved the analytical parameters of the system, with LoD 14.5 nM at the same potential. Therefore, as proof of concept, the PtNi/poly(AzA) film-based electrode was explored towards the suitability of an electrochemical sensor for the determination of hydrogen peroxide in aerosol phase. The outstanding features of the PtNi/poly(AzA) film-based electrode modified with the aforementioned ionic liquid allowed for the continuous monitoring of H2O2 in an aerosol stream generated with an ultrasonic diffuser at the low applied potential of 0.05 V. In addition, monitoring H2O2 samples through a series of ON/OFF switches for over 3 h, the sensor provided a fast and reproducible response.

Versatile FeMoOv nanozyme bipolar electrode electrochemiluminescence biosensing and imaging platform for detection of H2O2 and PSA

In this work, a unique FeMoOv nanozyme-bipolar electrode (NM-BPE) electrochemiluminescence (ECL) biosensing and imaging platform was proposed for the first time to realize sensitive detection of target hydrogen peroxide (H2O2) and prostate specific antigen (PSA). Considering the advantage that the cathode and anode poles of the bipolar electrode (BPE) can be modified respectively, this work was carried out using anode equipped with ECL reagent bipyridine ruthenium (Ru(bpy)32+), and cathode equipped with the Fe-doped molybdenum oxide/Au nanoparticles (FeMoOv/AuNPs) with excellent peroxidase (POD) and catalase (CAT)-like activity. Because FeMoOv/AuNPs show efficient enzyme catalysis effect and can greatly promote the decomposition of H2O2, thus the electron transfer rate in the NM-BPE system would be much accelerated to enhance the ECL signal of Ru(bpy)32+. Based on this principle, this work not only realized sensitive detection of H2O2, but also ingeniously designed an sandwich immunosensor using FeMoOv/AuNPs as recognition probe to mediate the ECL response on the anode, achieving highly sensitive detection of PSA. Furthermore, a unique mobile phone ECL imaging system was developed for assay of PSA at different concentrations, which opened a new portable imaging sensing device for bioassays. This work was the first time to combine nanozymes with bipolar electrodes for ECL analysis and imaging, which not only broadened the applications of nanozymes, but also pioneered the new joint ECL research technique of bipolar electrode and ECL imaging in bioassays, showing great application prospect for multiple detection of proteins, nucleic acids and cancer cells.

Electrochemical sensing of dual biomolecules in live cells and whole blood samples: A flexible gold wire-modified copper-organic framework-based hybrid composite

For clinical research, the precise measurement of hydrogen peroxide (H2O2) and glucose (Glu) is of paramount importance, due to their imbalanced concentrations in blood glucose, and reactive oxygen species (ROS) play a huge role in COVID-19 viral disease. It is critical to construct and develop a simple, rapid, flexible, long-term, and sensitive detection of H2O2 and glucose. In this paper, we have developed a unique morphological structure of MOF(Cu) on a single-walled carbon nanotube-modified gold wire (swnt@gw). Highly designed frameworks with nanotube composites enhance electron rate-transfer behavior while extending conductance and electroactive surface area.The composite sensing system delivers wide linear-range concentrations, low detection limit, and interference-free performance in co-existence with other biomolecules and metal ions. Endogenous quantitative tracking of H2O2 was performed in macrophage live-cells with the help of a strong stimulator lipopolysaccharide.The composite device was effectively utilized for the measurement of H2O2 and glucose in turbid samples of whole blood and milk samples without a pretreatment process. The practical results of biofluids showed favorable voltammetric results and acceptance recovery percentage levels between 97.49 and 98.88%. Finally, a flexible MOF-based hybrid system may provide a suitable detection platform in the construction of electro-biosensors and hold potential promise for clinical-sensory applications.