Peroxidase-like Catalyst Research Articles

Development of miniaturized fluorometric system for the detection of 4-hydroxybenzoic acid and benzoic acid in skincare products based on peroxidase-like catalysts

4-Hydroxybenzoic acid (PHBA) and benzoic acid are common preservatives in many skincare products. However, their excessive, long-term consumption can adversely affect internal and external organs. Herein, a small-volume fluorometric analysis method for preservatives, using PHBA and benzoic acid as model targets, was developed for the first time using Ni-MnFe-layered double hydroxides (Ni-MnFe-LDHs) as peroxidase-like mimics. Based on the intrinsic peroxidase-like activity of Ni-MnFe-LDHs, in the presence of preservatives, the generated hydroxy radical (•OH) from H2O2 decomposition was then consumed by PHBA or benzoic acid to form phenoxy radical, resulting in less •OH to oxidize o-phenylenediamine (OPD). On the other hand, in the absence of PHBA or benzoic acid, Ni-MnFe-LDHs and generated •OH could effectively catalyze OPD into the yellow-fluorescent product 2, 3-diamino phenazine. The fluorescence change of the solution captured by a smartphone under a UV-controlled lightbox was inversely related to preservative concentration. The detection platform was miniaturized using a 96-well plate. Under optimal conditions, with a total volume of only 100 µL, the developed sensing platform can quantitatively detect PHBA and benzoic acid in the concentration ranges of 0.008–1.0, with a limit of detections of 0.0011 and 0.0036 mmol L−1 for PHBA, and 0.0011 and 0.0040 mmol L−1 for benzoic acid, respectively. Our proposed method was successfully validated by quantitatively analyzing the residual preservatives in skincare samples, and the results showed agreement with those obtained using high-performance liquid chromatography.

Gold nanoclusters stabilized with dopa-containing ligands: Catalyst-indicator integrated probe for tumor cell screening

Elevated hydrogen peroxide (H2O2) levels not only inflict cellular damage but also serve as a harbinger for various diseases. Tumor cells, in particular, often exhibit an abundance of H2O2. Hence, the detection of this pivotal molecule assumes paramount importance in monitoring physiological states and expediting cancer diagnosis. To this end, we have ingeniously devised an enzyme-free and monomeric system for intracellular H2O2 detection. Our astute selection of dopa-containing peptidomimetics, replete with ortho-bisphenol and amino acid moieties, has engendered the synthesis of distinctive fluorescent gold nanoclusters (AuNCs). These nanoclusters not only function as a peroxidase-like catalyst, catalyzing the decomposition of H2O2 into hydroxyl radicals (·OH), but also serve as an indicator, with their fluorescence quenched in response to varying H2O2 concentrations. Experimental results evince that our GDpE-AuNCs exhibit remarkable sensitivity, boasting a detection limit of 0.49 μM and a linear range of 5–1000 μM. Moreover, the amalgamation of catalyst and indicator within a single structure, facilitating efficient cellular uptake, engenders intracellular H2O2 detection and discernment of tumor cells. This pioneering approach bequeaths a valuable assay probe for monitoring physiological states and ushering in early disease diagnosis.

Dual-mode colorimetric and photothermal aptasensor for detection of kanamycin using flocculent platinum nanoparticles

Chitosan (CS)-stabilized platinum nanoparticles (CS/PtNPs) were employed to develop a novel aptamer-based dual-mode colorimetric and photothermal biosensor for selective detection of kanamycin (KAN). As a peroxidase-like catalyst, the CS/PtNPs showed outstanding catalytic activity for the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2). As a stabilizing agent, CS excelled at fixing the KAN binding aptamer on the surface of the CS/PtNPs, amplifying their catalytic activity and enhancing colloidal dispersion and stability. The oxidized TMB (TMBox) functioned as a signal for the colorimetric, photothermal aptasensor because of its observable absorbance of light in the visible and near-infrared (NIR) regions. When light from a NIR laser was absorbed by the TMBox in the reaction solution, heat was generated in inverse proportion to the KAN concentration. The developed colorimetric and photothermal modes of the aptasensor showed a linear detection range of 0.1–50 and 0.5–50 μM, with a limit of detection (LOD) of 0.04 and 0.41 μM, respectively. Moreover, the aptasensor successfully determined KAN concentrations in spiked milk samples, verifying the reliability and reproducibility in practical applications. The dual-mode aptasensor based on CS/PtNPs for KAN detection, utilizing both color change and heat generation signals through a single probe (TMBox), demonstrates rapid response, simplicity in operation, cost-effectiveness, and high sensitivity. In addition, unlike typical immunoassays, this aptamer-based peroxidase-like nanozyme activation and inhibition strategy required no washing process, which was very effective in terms of reducing the time required for an assay and sustaining a high sensitivity.

Facile green synthesis of wasted hop-based zinc oxide nanozymes as peroxidase-like catalysts for colorimetric analysis.

Hops are a common ingredient in beer production, and a considerable quantity of hops is usually discarded as a waste material once the brewing process is completed. Transforming this waste material into valuable nanomaterials offers a sustainable approach that has the potential to significantly mitigate environmental impact. Herein, a facile and green protocol for the production of zinc oxide nanozymes (ZnO NZs) using wasted hop extract (WHE) as a natural precursor was demonstrated. The process involved a hydrothermal synthesis method followed by a calcination step to form the final ZnO NZs. The results revealed that lupulon, the main β-acid in hops, particularly the phenolic hydroxy group, is primarily responsible for the biosynthesis of ZnO NZs. The WHE-ZnO NZs exhibited exceptional peroxidase-like (POD-like) activity and served as effective catalysts for the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2). Analysis of the catalytic mechanism revealed that the POD-like activity of these WHE-ZnO NZs originated from their ability to expedite the transfer of electrons between TMB and H2O2, resulting in the enzymatic kinetics following the standard Michaelis-Menten mechanism. Furthermore, we developed a straightforward and user-friendly colorimetric technique for detecting both H2O2 and glucose. By utilizing the WHE-ZnO NZs as POD-like catalysts, we achieved a linear detection range of 1-1000 μM and a limit of detection of 0.24 μM (S/N = 3) for H2O2 detection and a linear range of 0-100 mM and a detection limit of 16.73 μM (S/N = 3) for glucose detection. These results highlighted the potential applications of our waste-to-resource approach for nanozyme synthesis in the field of analytical chemistry.

Green Synthesis of Iron Nanozymes Using Eucalyptus grandis Extract and Their Application as Peroxidase-Like Catalysts for H2O2 Quantification

In this work, iron nanoparticles were synthesized by a green and bio-inspired process, using Eucalyptus grandis extract as a reducing and stabilizing agent. The functional groups from the extract were incorporated into the structure of the nanoparticles, as confirmed by infrared spectroscopy. Characteristic peaks of zero-valence iron were observed by X-ray diffraction analysis, besides hematite and goethite. The nanoparticles showed spherical morphology and an average size of 96.4 nm. The zeta potential (|35| mV) indicated good stability. The nanoparticles were used as catalysts for o-phenylenediamine oxidation by H2O2, exhibiting optimal catalytic activity. The kinetic assays were performed, and the Michaelis-Menten model was adjusted to the data (maximum rate reached (Vmax) = 2.0 µmol L-1 s-1 and Michaelis-Menten constant (Km) = 307 µmol L-1). A spectrophotometric method was developed for H2O2 quantification. The analytical curve (18.3-112.6 µmol L-1) showed a good linear fit and limits of detection and quantification of 5.48 and 18.3 µmol L-1, respectively. Thus, the method is very promising, adhering to the principles of green chemistry.

Highly exposed Cu active sites as efficient peroxidase mimics for colorimetric analysis

Nanozymes are nanomaterials with intrinsic enzyme-mimic activity, but their large-scale application is generally limited by their low catalytic activity. Herein, we demonstrated that highly exposed Cu active sites on two-dimensional (2D) nitrogen-doped carbon (Cux/NC) can serve as efficient peroxidase-like (POD) catalysts with high atomic utilization. Specially, the uniformly distributed Cu active sites could react with H2O2 to produce singlet oxygen (1O2) under acidic conditions, which can efficiently oxidizes colorless 3,3′, 5,5′-tetramethylbenzidine (TMB) to blue oxidized TMB (oxTMB). Among various Cux/NC nanozymes studied, the Cu0.14/NC exhibited smaller maximum catalytic velocities (Vmax) and Menten constant (Km) for TMB and H2O2. Benefiting from the highly active peroxidase-like activity, the Cu0.14/NC nanozyme could be successfully applied for the hydroquinone (HQ) and ascorbic acid (AA) detection applications through the inhibitory effect of HQ and AA. More interestingly, α-glucosidase (α-Glu) detection sensing platform could be constructed based on HQ as a signal transmitter, with the detection range ranging from 0 to 12 U/L and the minimum detection limit being 0.68 U/L. This work provides not only an idea for the rational design of highly exposed Cu active sites but also fabricate an effective detection sensing platform for HQ, AA, and α-Glu detection.

Metal-phenolic networks derived CN-FeC hollow nanozyme with robust peroxidase-like activity for total antioxidant capacity detection

A tannate-iron network-derived peroxidase-like catalyst loaded with Fe ions on carbon nitride (C3N4) was reported for detection of total antioxidant capacity (TAC) in food in this study. Metal-phenolic networks (MPNs) was employed to form a low coordination compound on C3N4, and calcined catalyst formed hollow structure with abundant and uniform Fe sites and surface folds. CN-FeC exhibited significant peroxidase-like activity and high substrate affinity. The homogeneous distribution of amorphous Fe elements on the C3N4 substrate provides more active sites, resulting in provided excellent catalytic activity to activate H2O2 to ·OH, 1O2 and O2·–. The established CN-FeC/TMB/H2O2 colorimetric system can detect AA in the concentration range of 5‐40 μM, with the detection limits of 1.40 μM, respectively. It has good accuracy for the detection of vitamin C tablets, beverages. Taken together, this work shows that metal-phenolic networks can be an effective way to achieve efficient utilization of metal atoms and provides a promising idea for metal-phenolic networks in nanoparticle enzyme performance enhancement.

DNA flexible chain modified MOFs as a versatile platform for chemoenzymatic cascade reactions in glucose catalysis

Glucose oxidase (GOD) is widely used in the pharmaceutical industry, fermentation products and glucose biosensors for its essential role in catalyzing the conversion of glucose to gluconic acid and hydrogen peroxide (H2O2). As H2O2 is the by-product and will have a toxic effect on glucose oxidase, so introducing another enzyme that could consume H2O2 to form an enzymatic cascade reaction is a practical solution. However, this decision will lead to extra expenses and complex condition optimization such as the specific mass ratio, temperature and pH to improve the activity, stability and recyclability. Herein, we describe a mild and versatile strategy by anchoring GOD on carboxyl-activated MOF (Cu-TCPP(Fe)) through DNA-directed immobilization (DDI) technology. Robust MOF nanosheets were utilized as not only the carrier for the immobilization of GOD, but also a peroxidase-like catalyst for the decomposition of H2O2 to reduce its harmful impacts. In this work, the immobilized GOD retained 55.78% of its initial activity after being used for 7 times. More than 60% of the immobilized enzyme's catalytic activity was still maintained after 96 h of being stored at 50 ℃. This study provides a new idea for preparing immobilized enzymes with enhanced stability, fast diffusion and high activity, which can be used in fields such as biocatalysis and biotechnology.

Polymeric membrane with nanohybrids of Cu nanocomposites and metalloporphyrin-based nanosheets for enzyme-like catalytic degradation of Congo Red

Metalloporphyrin-based nanozymes are effective peroxidase-like catalysts for dye degradation; however, their reusability is a challenge due to the nanoscale dimensions. Membrane technology has the advantages of high efficiency, low energy consumption, and easy operation. Here, we integrate poly (vinylidene fluoride) (PVDF) membrane with nanozyme for effective decolorization of Congo Red (CR). A nanozyme (Cu@Cu-FeTCPP) is prepared by growth of copper hydroxide-copper oxide (Cu(OH)2-CuO) nanocomposites onto the metal organic framework (MOF) nanosheet consisting of tetrakis-(4-carboxyphenyl)-porphyrin iron ligands and cupric ion nodes. The functional membrane is achieved by loading Cu@Cu-FeTCPP nanozyme on the PVDF membrane surface (Cu@Cu-FeTCPP/PVDF). The as-prepared membrane shows catalytic activity for the degradation of CR. Under flow through conditions, the catalytic degradation in tangential flow plays a major role in overall decolorization of CR, far exceeding the contribution of adsorption. The membrane can rapidly catalyze the dye degradation even at different operating pressures (0.1–0.7 kPa) and feed solutions with higher CR concentrations (eg. 60 mg·L-1). Compared with the static batch catalysis and the free nanozyme catalysis, the membrane exhibits higher decolorization efficiency and outstanding reusability in the continuous flow process owing to the promoted mass transfer. After 40 min of continuous flow reaction in a feed solution containing CR (40 mg·L-1) and H2O2 (50 mM), the decolorization efficiency approaches 90% and remains above 85% after five catalytic cycles. The membrane with enzyme-mimicking ability has application prospect in wastewater treatment.

Adaptable graphitic C6N6-based copper single-atom catalyst for intelligent biosensing

Self-adaptability is highly envisioned for artificial devices such as robots with chemical noses. For this goal, seeking catalysts with multiple and modulable reaction pathways is promising but generally hampered by inconsistent reaction conditions and negative internal interferences. Herein, we report an adaptable graphitic C6N6-based copper single-atom catalyst. It drives the basic oxidation of peroxidase substrates by a bound copper-oxo pathway, and undertakes a second gain reaction triggered by light via a free hydroxyl radical pathway. Such multiformity of reactive oxygen-related intermediates for the same oxidation reaction makes the reaction conditions capable to be the same. Moreover, the unique topological structure of CuSAC6N6 along with the specialized donor-π-acceptor linker promotes intramolecular charge separation and migration, thus inhibiting negative interferences of the above two reaction pathways. As a result, a sound basic activity and a superb gain of up to 3.6 times under household lights are observed, superior to that of the controls, including peroxidase-like catalysts, photocatalysts, or their mixtures. CuSAC6N6 is further applied to a glucose biosensor, which can intelligently switch sensitivity and linear detection range in vitro.

Tuning Fe3O4 for sustainable cathodic heterogeneous electro-Fenton catalysis by acetylated chitosan

Peroxidase-like catalysts are safe and low-cost candidates to tackle the dilemma in constructing sustainable cathodic heterogeneous electro-Fenton (CHEF) catalysts for water purification, but the elusive structure-property relationship of enzyme-like catalysts constitutes a pressing challenge for the advancement of CHEF processes in practically relevant water and wastewater treatment. Herein, we probe the origins of catalytic efficiency in the CHEF process by artificially tailoring the peroxidase-like activity of Fe3O4 through a series of acetylated chitosan-based hydrogels, which serve as ecofriendly alternatives to traditional carbon shells. The optimized acetylated chitosan wrapping Fe3O4 hydrogel on the cathode shows an impressive activity and stability in CHEF process, overcoming the complicated and environmentally unfavored procedures in the electro-Fenton-related processes. Structural characterizations and theoretical calculations reveal that the amide group in chitosan can modulate the intrinsic redox capacity of surficial Fe sites on Fe3O4 toward CHEF catalysis via the neutral hydrogen bond. This work provides a sustainable path and molecule-level insight for the rational design of high-efficiency CHEF catalysts and beyond.

H2O2 activation over Cu-Schiff bases nanozyme for the removal of amlodipine: Kinetics, mechanism and toxicity evaluation

Artificial nanozyme is a promising alternative approach to replace natural enzyme and promote their industrialization. For designing artificial enzymes, the structure of the ligand is one of the important factors which needs to be considered. Schiff bases as special donor ligands could effectively stabilize active metal ions, endowing them playing important roles in the field of artificial enzymes. Herein, we focused on constructing a Schiff base metal complex with peroxidase-like activities to achieve efficient activation of hydrogen peroxide (H2O2) for the removal of amlodipine (AML). Polydopamine (PDA) and 3, 5-dibromosalicylaldehyde (DBSA) were used as raw materials to synthesize the Schiff base (DPDA), and Cu2+ is used for the coordination reaction to synthesize the Schiff base metal complex (Cu@SB). Our results demonstrated the prepared Cu@SB effectively activated H2O2 to degrade AML, and the removal of AML followed a pseudo first-order kinetic model. Electron paramagnetic resonance (EPR) tests and quenching tests showed •OH and 1O2 were responsible for removing AML. X-ray photoelectron spectroscopy (XPS) analysis implied the redox reaction of Cu(I)/Cu(II) participated in the catalytic process. Three major transformation pathways including dehydrogenation, oxidative deamination and hydroxylation were proposed based on density functional theory (DFT) calculations and LC-MS/MS analysis. Moreover, it was discovered that the toxicities of most intermediates were lower than AML. Overall, this study provides new insights into constructing peroxidase-like catalysts used for the efficient activation of H2O2 to remove emerging organic pollutants in water, broadening the application of Schiff bases in wastewater treatment.

A new application of papain: As a peroxidase-like catalyst for fluorometric detection of uric acid

Papain, as a classical cysteine protease, has been widely used in the food, pharmaceutical, chemical, and cosmetic fields. However, there are few information about the peroxidase-like activity of papain catalyzed substrate to produce fluorescence. In this study, we found that papain can catalyze H2O2 to convert o-phenylenediamine (OPD), and generate fluorescence emission at 550 nm under 430 nm excitation. Based on this foundation, we report a papain/OPD/H2O2 system for fluorescence detection of uric acid. The method exhibits a wide linear range of 10–1000 μM with a limit-of-detection of 4.6 μM, and has been successfully used to detect uric acid in human serum. This study paves the way for the application of papain as catalyst for fluorescence detection of different target biomolecules, such as cholesterol, glucose, lactate, for which H2O2 is a product of oxidoreductase enzymes.

Colorimetric detection of H2O2 by peroxidase-like catalyst iron-based nanoparticles synthesized by using hyperaccumulator plant-derived metal solution

H2O2, a by-product of many enzymatic reactions, plays an important role in various fields such as the food industry, cosmetics, textile, electronics, mining, paper, medicine, environmental chemistry, biological analysis, and clinical diagnosis; so, the quantitative detection of it is of great importance. In this work, the iron-based nanoparticles (FeNPs), as a peroxidase-like catalyst for the colorimetric detection of H2O2, were synthesized by using the acidic leaching solution of an iron hyperaccumulator plant, Pinus brutia. The experimental results proved that FeNPs exhibited strong intrinsic peroxidase-like activity and could efficiently catalyze the oxidation of chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2. The catalytic reaction by FeNPs was in accordance with typical Michaelis–Menten kinetics, which showed that FeNPs possessed a much higher affinity to H2O2 and TMB than horseradish peroxidase (HRP). FeNPs were utilized as a peroxidase-like catalyst for the detection of H2O2 in a relatively wide range of 0.05–0.20 mM with a lower detection limit of 0.05773 μM. In brief, this work reported the first use of iron-based nanoparticles synthesized from a hyperaccumulator plant in the sensitive, selective, and reliable detection of H2O2, which may promote the development of new peroxidase-like nanocatalysts for colorimetric detection applications.

A Comparative Study of Biomimetic Synthesis of EDOT-Pyrrole and EDOT-Aniline Copolymers by Peroxidase-like Catalysts: Towards Tunable Semiconductive Organic Materials.

It has been two decades since biomimetic synthesis of conducting polymers were first reported, however, the systematic investigation of how catalysts influence the properties of the conducting polymers has not been reported yet. In this paper, we report a comparative study between peroxidase-like catalyst, dopants, and their effect on the properties of poly (3,4-ethylenedioxythiophene) (PEDOT), polypyrrole (PPY), and polyaniline (PANI). We also investigate the EDOT-Pyrrole and EDOT-Aniline copolymerization by enzymomimetic synthesis using two catalysts (Ferrocene and Hematin). It was found that, chemically, there are no detectable effects, only having small contributions in molar ratios greater than 0.7–0.3. Spectroscopic data provide solid evidence concerning the effect in the variation of the molar fractions, finding that, as the molar fraction of EDOT decreases, changes associated with loss of the conjugation of the structure and the oxidation state of the chains were observed. The electrical conductivity was considerably modified depending on the type of catalyst. Hematin produces conductive homopolymers and copolymers when doped with p-toluene sulfonic acid (TSA), while ferrocene produces low conductive copolymers under the same conditions. The mole fraction affects conductivity significantly, showing that as the EDOT fraction decreases, the conductivity drops drastically for both EDOT-PY and EDOT-ANI copolymers. The type of dopant also notably affects conductivity; the best values were obtained by doping with TSA, while the lowest were obtained when doping with polystyrene sulfonate (PSS). We also draw a biomimetic route to tailor the fundamental properties of conducting homopolymers and copolymers for their design and scaled-up production, as they have recently been found to have use in a broad range of applications.

Double-signal quantification of amoxicillin based on interaction with 4-aminoantipyrine at copper and nitrogen co-doped carbon quantum dots as an artificial nanozyme.

Anone-pot hydrothermal method was developed for synthesis of carbon quantum dots co-doped with copper and nitrogen (Cu, N@CQDs). The synthesized Cu, N@CQDs has unique advantages such as high fluorescence quantum yield (39.1%) and high catalytic activity. Oxidative coupling of amoxicillin (AMX) with 4-aminoantipyrine (4-NH2-APE) in the presence of H2O2 as an oxidant to produce pink quinoneimine chromogen was carried out with the aid of Cu, N@CQDs as a peroxidase-like catalyst. This system was used for the colorimetric and fluorometric assays of AMX with reliable results. Colorimetric method is based on the measurement of a pink-colored product at λmax = 505nm while the fluorometric assay is based on the quenching of the fluorescence emission of Cu, N@CQDs at 440nm after excitation at 370nm. For the colorimetric method, the absorption intensity linearly increased over the concentration range 4.3-110.0µM with LOD (S/N = 3) of 1.3µM. For the fluorometric method, the emission intensity of Cu, N@CQDs linearly decreased upon addition of AMX in the concentration range 0.2-120.0µM with a limit of detection (LOD, S/N = 3) of 0.06µM. The proposed system was applied tothe determination of AMX in different real samples such as pharmaceutical capsules, human serum, milk, and conduit water samples with recoveries in the range 95.8-104.1% and relative standard deviation (RSD %) less than 4.1%.

Magnetic Biochar-Supported Pd Nanoparticles as a Peroxidase-Like Catalyst

Magnetic Biochar-Supported Pd Nanoparticles as a Peroxidase-Like Catalyst

Thiolated Ligand-Functionalized MoS2 Nanosheets for Peroxidase-like Activities

Nanozymes, a class of nanomaterials that mimic the catalytic activity of natural enzymes, could be used to control the rapid spread of infectious diseases. Here, we have demonstrated that the intrinsic peroxidase-like activity of two-dimensional molybdenum disulfide (2D-MoS2) nanosheets can be amplified through surface functionalization. Traditionally, hydrogen peroxide (H2O2) has been widely used as a universal disinfectant agent but requires a high concentration. This can be taken care by the presence of any peroxidase-like catalyst to reduce the concentration of H2O2. Herein, we have explored the effect of surface functionality on peroxidase-like nanozyme activity of 2D-MoS2 nanosheets. We observed that functionalization of 2D-MoS2 nanosheets not only enhances the aqueous stability but also exhibits remarkably high peroxidase-like activity. Subsequently, we have extended this effect toward antibacterial activity in the presence of H2O2. The combination of the specific functionalized 2D-MoS2 nanomaterial of a concentration of 5.6 I¼g/mL and H2O2 of a concentration of only 0.5 mM (17642 times dilution of the commercially available 30 H2O2 solution) showed an excellent antibacterial activity compared to H2O2 alone. This work established that proper surface modification of various nanomaterials with intrinsic nanozyme properties can enhance the activity, which can be applied for many other related applications such as disinfectants, biosensors, drug delivery, and so forth. © 2021 American Chemical Society.

Vanadium/cobalt oxides–anchored flexible carbon nanofibers with tunable magnetism as recoverable peroxidase-like catalysts

High-efficiency peroxidase-like catalysts that can be easily recycled are desperately needed for the rapid and accurate detection of H2O2. Herein, a novel flexible membrane composed of vanadium/cobalt oxides–anchored carbon (VCoO/C) nanofibers has been purposely designed and fabricated by electrospinning and subsequent carbonization, where there are processing temperature-dependent morphology, composition, and versatile properties. As the carbonization temperature increases from 600°C to 900°C, the saturation magnetization of the as-prepared VCoO/C nanofibers rises gradually. When treated at 750°C under Ar protection, the resultant VCoO/C-750 nanofibers yield superior peroxidase-like catalytic activity toward H2O2 with a low limit of detection of 0.44 μM (signal-to-noise ratio = 3). The combination of magnetic behavior and flexibility enables the effective recovery of catalysts. It is believed that our results will open a new avenue for the controlled preparation of flexible nanofiber materials, which are endowed with multiple functions.

Rapid and highly sensitive colorimetric biosensor for the detection of glucose and hydrogen peroxide based on nanoporphyrin combined with bromine as a peroxidase-like catalyst

Peroxidase is a popular amplifier of biosensor signals, but its application is limited by chemical instability and expensive purification. We developed a sensitive, novel colorimetric biosensor to detect glucose and hydrogen peroxide (H2O2) using Zinc tetrakis (4-pyridinyl) porphyrin (ZnTPyP)-dodecyl trimethyl ammonium bromide (DTAB) nanoparticles (NPs) as peroxidase-like catalysts. ZnTPyP-DTAB NPs can oxidize colorless 3, 3’, 5, 5’-tetramethylbenzidine to a blue product (652 nm) in the presence of H2O2via electron transport between porphyrin and bromine. This peroxidation mechanism was further verified using quantum chemical calculations. The detection limits of the colorimetric ZnTPyP-DTAB NP sensor were 0.15 and 0.5 μmol L−1 for glucose and H2O2, respectively, and the linear range was 3–70 and 8–50 μmol L−1, respectively. Recovery ratios of the biosensor in spiked human serum and saliva samples were 100 % ± 10 %. This simple method is robust, color stable, and reliable, thus providing an effective colorimetric biosensing platform for biomedical diagnosis.