Peroxidase Mimetics Research Articles

3DRGO-NiFe2O4/NiO nanoparticles for fast and simple detection of organophosphorus pesticides

The residues of organophosphorus pesticide (OPs) on fruits and vegetables pose a threat to human health, so it is very meaningful to explore simple and fast detect methods for OPs residual. In this work, nickel ferrite/nickel oxide nanoparticles co-loaded three-dimensional reduced graphene oxide (3DRGO-NiFe2O4/NiO NPs), as a new low cost nanocomposite, was prepared. Based on its high performance mimetic peroxidase activity, a colorimetric method for the detection of OPs has been developed. Dichlorvos was chosen as model compounds to evaluate the detection performance. The detection linear range for dichlorvos is from 50 μg/mL to 2.5 × 104 μg/mL with a detection limit of 10 μg/mL. Furthermore, a test paper can be developed based on the 3DRGO-NiFe2O4/NiO NPs for visual detection of dichlorvos, and the image information of the paper sensor can be converted into digital signal and quantitative detection by a smartphone. Notably, this method can also be used to detect dichlorvos in real samples, including vegetables and fruits. Thus, the developed naked assay holds great potential in simple, inexpensive and rapid detection of OPs in fruit and vegetable samples.

Novel acidic eutectic mixture as peroxidase mimetics for oxidative desulfurization of model diesel

A new generation of green solvent, deep eutectic solvents (DESs), are being received increased interest in the fields of organic synthesis, electrochemistry, catalysis and oxidative desulfurization (ODS) process. Despite possessing high ODS activity, little is known for the mechanism of the excellent desulfurization performance of DES. In this study, a class of acidic eutectic mixture was prepared with different molar ratios of acetamide and glutaric acid. It was found that desulfurization process was significantly affected by the composition of prepared DES. Under optimal conditions, the desulfurization efficiencies of acetamide/glutaric acid (molar ratio 1 : 2) DES was capable to reach up to 99% within only 3 h.Density functional theory (DFT) calculation revealed that acetamide/glutaric acid DES possessed intrinsic peroxidase-like property and reduced greatly TS barriers in oxidation process. The synergy cooperation of acetamide and carboxylate likes the active site of enzyme, achieving the catalytic oxidation of dibenzothiophene (DBT). In addition, this DES system was successfully applied for the deep oxidation desulfurization of real fuels, which demonstrated extraordinary catalytic performances.

Fabrication of polyethyleneimine-functionalized reduced graphene oxide-hemin-bovine serum albumin (PEI-rGO-hemin-BSA) nanocomposites as peroxidase mimetics for the detection of multiple metabolites

The ultrasensitive bioassays are increasingly demanded for disease diagnosis and environmental monitoring. The combined unique natures of the components in nanocomposites have led to their wide applications in bioanalysis. In the current study, a simple strategy for preparing polyethyleneimine-functionalized reduced graphene oxide-hemin-bovine serum albumin (PEI-rGO-Hemin-BSA) nanocomposites as peroxidase mimetics was demonstrated. The developed nanocomposites of PEI-rGO-Hemin-BSA showed an excellent peroxidase-like activity. Importantly, through the glutaradelhyde crosslinking, PEI-rGO-Hemin-BSA could be further simply combined with various oxidases such as glucose oxidase, cholesterol oxidase, lactate oxidase and choline oxidase for the detection and quantitative measurement of multiple metabolites including glucose, cholesterol, l-lactate, and choline. The developed detection strategy, which is sensitive, convenient, low-costed, and in tiny sample consumption, could be expected wide applications in the disease diagnosis and management of metabolite disorders.

One-pot fabrication of Fe-doped carbon nitride nanoparticles as peroxidase mimetics for H2O2 and glucose detection.

Iron-doped carbon nitride nanoparticles (Fe-CNNPs) were prepared from citric acid, urea and ferric chloride through a convenient one-pot solvothermal method. Oleic acid was used as the reaction medium. The morphology and chemical composition of the obtained Fe-CNNPs were characterized by multiple methods including transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). It is interesting to find that the Fe-CNNPs showed higher catalytic activity than horseradish peroxidase (HRP), and tetramethylbenzidine (TMB) can be catalytically oxidized in the presence of H2O2 to produce a color change in aqueous solution. As H2O2 can be generated in the oxidation process of glucose catalyzed by glucose oxidase (GOD), a novel sensitive method for the detection of glucose with a limit of detection (LOD) of 0.29 μM has been developed combined with the catalytic properties of GOD and Fe-CNNPs. The Fe-CNNPs with peroxidase mimetics activity may have potential applications in biotechnology field.

Ratiometric fluorescence based on silver clusters and N, Fe doped carbon dots for determination of H2O2 and UA: N, Fe doped carbon dots as mimetic peroxidase

In this study, a dual-emission ratiometric fluorescent sensing system is developed for the analysis of H2O2 and uric acid (UA). This sensing system is based on N, Fe-doped carbon dots (N, Fe-CDs) and bovine serum albumin (BSA)-stabilized silver nanoclusters (BSA-Ag NCs) with peroxidase activity. By the catalysis of uriase, UA was oxidized by oxygen dissolved in the solution and H2O2 is produced. The carbon site with peroxidase activity can catalyze H2O2 to generate hydroxyl radicals, which etches to the BSA-Ag NCs. At the excitation wavelength of 390 nm, there were dual emission peaks at 450 nm and 650 nm. With increasing concentration of H2O2 or UA, the red fluorescence at 650 nm for BSA-Ag NCs decreases due to the etching of BSA-Ag NCs by hydroxyl radicals, while the blue fluorescence of N, Fe-CDs is restored. Based on the relationship between the fluorescence intensity ratio (I450/I650) to detect H2O2 and UA, the linear range of H2O2 was 0.6–100 μM with a detection limit of 0.30 μM (S/N = 3), while the linear range of UA was 0.8–133 μM with a detection limit of 0.49 μM (S/N = 3). Moreover, the present method was used for the analysis of UA in human urine with satisfactory accuracy as well as recovery. This ratiometric fluorescent approach can be used for analysis of UA and H2O2 for biomedical applications.

Design and Characterization of a Novel Artificial Peroxidase

In this study, we reported on a novel mimetic peroxidase, deuterohemin–Ala–His–Glu, (Dh–A–H–E). The kinetic parameters of Dh–A–H–E suggested that it was a mimetic peroxidase and followed the ping–pong mechanism. Compared to horseradish peroxidase, Dh–A–H–E exhibited excellent stability when tested at different pH and temperatures, and using different organic solvents. Based on our above results, a new method using Dh–A–H–E has successfully been developed for the fast and quantitative detection of trace amounts of glucose.

Amperometric biosensors based on oxidases and PtRu nanoparticles as artificial peroxidase

Catalytically active nanomaterials have several advantages over their natural analogues when used as artificial enzymes (nanozymes), namely, higher stability and lower cost. Nanozymes with metallic nanocomposites are promising catalysts for biosensing applications. The aim of the current research is to construct oxidase-based bioelectrodes for food analysis using nanozymes as peroxidase mimetics. Bimetallic PtRu nanoparticles (nPtRu) coupled with alcohol oxidase (AO) and methylamine oxidase (AMO) were chosen to construct amperometric biosensors (ABSs) for primary alcohols and methylamine (MA). Both ABSs show high sensitivities (336 A·M−1·m−2 for the AO-ABS and 284 A·M−1·m−2 for the AMO-ABS), broad linear ranges (25–200 µM ethanol and 20–600 µM MA) and satisfactory storage stabilities. Practical feasibility of the constructed ABSs was demonstrated on food samples. High correlation between contents of MA and ethanol in foods determined by the ABSs and reference methods was observed.

Fabricated nanoplatform of Cu(II)-functionalized mimetic-peroxidase with catalytic property toward sensitive monitoring of hydrogen peroxide

A novel strategy toward monitoring of hydrogen peroxide (H2O2) through carbonaceous nanoplatform architectures (herein named as Cu(II)-LPQDs) is presented. Cu(II)-LPQDs were constructed by coupling Cu(II) complex with l-phenylalaninamide (LPN) functionalized N-doped carbon quantum dots (LPQDs). We have designed an efficient metal-ion-controlled mechanism to control peroxidase mimetic catalytic reactions. As the range of electron delocalization enhanced, the catalytic activity and stability of the mimetic peroxidase based on the Cu-N coordination unit increase significantly. By capturing the appearance of colorimetric and fluorescence changes, the detection of H2O2 in biological samples by qualitative and quantitative analysis is successfully realized. In our work, the detection limits of H2O2 by colorimetric and fluorescent methods are 80 nM and 2.5 μM, respectively. Its ultrasensitive-bidirectional properties are well described in-situ measurement in real samples and biological cells. The arresting feature of this method is green, simple, speedy, selective, sensitive and stable. Our findings provide clues to the intelligent nanoplatforms for the preparation of metalloenzymes without the use of noble metal elements for sensing applications and exhibit the highest peroxidase mimetic activity compared to other transition metals.

Unusual N,Se-heterocycles with cyclic Se–N+ bond of isoselenazolopurinium type

Treatment of 8-alkynylcaffeine or -adenine derivatives with in situ generated SeBr4 caused their annulation with the formation of isoselenazolium ring. The salts obtained are regarded as glutathione peroxidase mimetics.

MOFzyme: Enzyme Mimics of Fe/Fe-MIL-101

In this work, metal-organic frameworks (MOFs) Fe-MIL-101 was synthesized by hydrothermal method, and Fe/Fe-MIL-101 with different loadings was prepared. The crystal structure of the Fe/Fe-MIL-101 sample was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and specific surface area measurement (BET). Fe/Fe-MIL-101 was found to posses an intrinsic enzyme mimicking activity similar to that found in natural horse-radish peroxidase (HRP). The Michaelis constant (Km) of 5% Fe/Fe-MIL-101 with ABTS as the substrate is about 10-fold smaller than Fe-MIL-101 and about 3-fold smaller than HRP, and about 108 times less than that of CuO NPs (Km = 10.28 mM), indicating a much higher affinity for ABTS than HRP and most of the peroxidase mimetics.

Synthesis of ZnFe2O4/ZnO heterostructures decorated three-dimensional graphene foam as peroxidase mimetics for colorimetric assay of hydroquinone

The 3D ZnO/ZnFe2O4/graphene foam (ZZFO/GF) was successfully prepared by template method and hydrothermal process as a sensing platform for colorimetric detection of hydroquinone (HQ). It is found that the foam exhibited improved peroxidase-like activity that could quickly catalyze 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2 and produced a blue color, which can be observed by naked eyes. And the HQ was detected by means of fading the color of the oxTMB, which is a sensitive and simple colorimetric method that is rarely used for detection of HQ. Therefore, a simple, sensitive and selective sensing platform was established. A good linear range from 0 to 150 μM and low detection limit of 3.75 μM was achieved. Furthermore, the materials could be easily recollected by applying a magnetic field. This method exhibited practical potential in environmental pollutant analysis and actual detection of HQ in local river water was achieved.

Colorimetric determination of Hg2+ in environmental water based on the Hg2+-stimulated peroxidase mimetic activity of MoS2-Au composites

A colorimetric assay is described for sensitive determination of Hg2+ ions based on the MoS2-Au composites as peroxidase mimetics, which are synthesized by microwave-assisted solvothermal method. The addition of Hg2+ stimulates their peroxidase-like activity, along with lower Michaelis constant toward the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) with H2O2, allowing the composites for direct determination of Hg2+. A broad linear response is obtained ranging from 20 nM to 20 μM with a detection limit (LOD) of 5 nM. The superior peroxidase-like activity is attributed to the large surface area of MoS2 nanosheets and the synergistic catalytic effect of MoS2 and Au. The Hg2+-stimulation effect implies the strong interaction between Hg2+ and MoS2-Au, where the XPS results confirm the presence of metallic Hg0, indicative of an Au-Hg amalgam. This colorimetric assay is successfully applied for the determination of Hg2+ in environmental water (tap water and Yellow River water) with excellent selectivity over interfering cations.

Competitive method for fluorescent dopamine detection in cerebrospinal fluid based on the peroxidase-like activity of ficin.

Dopamine (DA), a catecholamine neurotransmitter, is considered to be an important indicator for mental diseases detection in the clinic. In this study, a novel fluorescent sensing platform consisting of the ficin-H2O2-tyramine system for determining DA in cerebrospinal fluids (CSF) was established. The proposed method is based on the fact that ficin, a mimetic peroxidase, can catalyze H2O2 decomposition into OH radicals, which can oxidize non-fluorescent tyramine into fluorescent dityramine. When DA was introduced, DA can compete with tyramine for OH and resulting in the oxidation reaction of tyramine inhibited along with the fluorescence intensity of the system decreased, which provides a unique strategy for fluorescence detection of DA. Under optimal conditions, the fluorescence intensity decreased linearly with the DA level over a wide concentration range from 0.05 to 12.0 μM (R2 = 0.995) with a detection limit of 46 nM (3σ/k). More importantly, the proposed sensing approach exhibits high sensitivity, good selectivity and has been successfully applied to DA sensing in complex biological samples, which made it hold great potential for DA determination in chemical and biological analytical applications.

Silver-gold-apoferritin nanozyme for suppressing oxidative stress during cryopreservation

Reactive oxygen species (ROS) cause oxidative stress, which involves in the pathogenesis of many serious diseases. Apoferittin containing gold-silver nanoparticles (Au-Ag-AFT) was designed and evaluated as a nanozyme for scavenging the ROS. The nanozyme consisting of silver-gold nanohybrid in apoferittin cage represents superoxide dismutase, catalase and peroxidase mimetic activities. The Au-Ag-AFT nanozyme was characterized by spectroscopy, FESEM, TEM and dynamic light scattering. The inhibition process for pyrogallol autoxidation was used for assaying the superoxide dismutase mimetic activity and measuring the kinetic parameters of Au-Ag-AFT nanozyme. Additionally, Aebi method and standard protocol was used for evaluating the catalase and peroxidase mimetic activity. The kcat values for superoxide dismutase, catalase and peroxidase mimetics activity were 1.4 × 106, 0.1 and 9 × 103 s−1 respectively. These values indicated that Au-Ag-AFT nanozyme could act as a suitable ROS scavenger. Additionally, Au-Ag-AFT nanozyme was examined as a protective agent for human sperm against oxidative stress induced during the cryopreservation process. Presence of the nanozyme in the sperm media significantly increased the motility and viability of the cells and also decreased the ROS, apoptosis and necrosis (P < 0.05) compare to the control group.

Hybrid Hydrogels Based on insitu Interpenetrating Networks Graphene Oxide (GO) and Au Nanoparticles, and Its Application as Peroxidase Mimetics for Glucose Detection

AbstractGraphene oxide (GO) and Au Nanoparticles (NPs) hybrid hydrogels were prepared through one‐step hydrothermal method. The microstructure of GO/AuNPs hydrogels determined by SEM demonstrated that the hydrogels displayed three‐dimensional (3D) network structure. The freeze‐dried GO/AuNPs hydrogels (xerogels), i. e., GO/Au nanocomposites, could efficiently catalyze the oxidation reaction of peroxidase substrate, 3,3′,5,5′‐tetramethylbenzidine (TMB), in the presence of H2O2 to produce a blue color reaction. Compared with the natural enzyme, horse radish peroxidase (HRP), GO/Au nanocomposites exhibited higher peroxidase‐like activity. The reason might be that the porous 3D network structure of GO/Au nanocomposite enhanced the reaction activity. The catalytic reaction mechanism of GO/Au nanocomposite was followed the Michaelis‐Menten behavior. The combination of GO/Au nanocomposite with glucose oxidase (GOx) performed a selective colorimetric assay for glucose detection with a detection limit of 0.4728 μmol⋅L−1, which can be used as a promising candidate biosensor for glucose detection.

Preparation of porphyrin modified CO9S8 nanocomposites and application for colorimetric biosensing of H2O2

Hydrogen peroxide detection has been widely applied in the fields of biology, medicine, and chemistry. Colorimetric detection of hydrogen peroxide has proven to be a fast and convenient method. In this work, 5,10,15,20-tetrakis(4-chlorophenyl) porphyrin modified Co[Formula: see text]S[Formula: see text] nanocomposites (H[Formula: see text]TClPP-Co[Formula: see text]S[Formula: see text] were prepared via a facile one-step hydrothermal method. H[Formula: see text]TClPP-Co[Formula: see text]S[Formula: see text] nanocomposites were demonstrated to possess an enhanced mimetic peroxidase activity toward the substrate, 3,3[Formula: see text],5,5[Formula: see text]-tetramethylbenzidine (TMB), which can be oxidized to oxTMB (oxidized TMB) in a buffer solution of hydrogen peroxide with a color change from colorless to blue. The catalytic activity of H[Formula: see text]TClPP-Co[Formula: see text]S[Formula: see text] was further analyzed by steady-state kinetics, and H[Formula: see text]TClPP-Co[Formula: see text]S[Formula: see text] had high affinity towards both TMB and H[Formula: see text]O[Formula: see text]. Furthermore, fluorescence and ESR data revealed that the catalytic mechanism of the peroxidase activity of H[Formula: see text]TClPP-Co[Formula: see text]S[Formula: see text] is due to hydroxyl radicals generated from decomposition of H[Formula: see text]O[Formula: see text]. Based on the catalytic activity of H[Formula: see text]TClPP-Co[Formula: see text]S[Formula: see text], a sensitive colorimetric sensor of H[Formula: see text]O[Formula: see text] with a detection limit of 6.803 [Formula: see text]M as well as a range of 7–100 [Formula: see text]M was designed.

Co3O4–Au Polyhedra: A Multifunctional Signal Amplifier for Sensitive Photoelectrochemical Assay

Taking the zeolitic imidazolate framework (ZIF-67) as the precursor, p-type semiconducting Co3O4-Au polyhedra were synthesized and used as the signal amplifier to construct a sensitive photoelectrochemical (PEC) sensor for caspase-3 activity assay. Here, the n-type semiconductor Bi2S3-modified indium-tin oxide (ITO) slice was used as the photoelectrode. After immobilization of the biotin-DEVD-peptide (biotin-Gly-Asp-Gly-Asp-Glu-Val-Asp-Cys) onto the Bi2S3 surface, the streptavidin-labeled Co3O4-Au polyhedra were introduced to the sensing platform via the specific interaction between biotin and streptavidin. The Co3O4-Au polyhedra can not only quench the photocurrent of the Bi2S3 because of the competitive consumption of electron donors and exciting light energy (p-n-type semiconductor quenching effect), but also act as peroxidase mimetics to produce catalytic precipitate. Additionally, the steric hindrance effect from the Co3O4-Au polyhedra will decrease the PEC response of the Bi2S3. Ingeniously, the precipitates can not only deposit on the ITO electrode to decrease the photocurrent of PEC sensor, but also act as electron acceptors to scavenge the photogenerated electrons of Co3O4-Au polyhedra, leading to enhanced quenching ability of the Co3O4-Au polyhedra. When caspase-3 exists, caspase-3 can specifically recognize and cleave the biotin-DEVD-peptide, resulting in the increase of PEC response. Based on the multifunctional Co3O4-Au polyhedra, caspase-3 is detected sensitively with a linear range from 0.5 to 50 ng mL-1 and limit of detection down to 0.10 ng mL-1. The Co3O4-Au polyhedra provide a novel signal amplifier to construct PEC sensing platform and may have potential applications in bioanalysis, disease diagnostics, and clinical biomedicine.

Ultra-small CuS Nanoparticles as Peroxidase Mimetics for Sensitive and Colorimetric Detection of Uric Acid in Human Serum

Abstract As the main final products of the purine metabolism in human body, uric acid (UA) usually presents in serum and urine. Thus, the level of UA in biology is closely related to human health. In this work, the ultra-small CuS nanoparticles (NPs) were demonstrated to possess intrinsic peroxidase-like activity towards 3,3',5,5'-tetramethylbenzidine (TMB) substrate in the presence of H2O2, which yielded the blue oxidized TMB (oxTMB) with strong absorption at 653 nm. Furthermore, H2O2 could be produced by the enzymatic reaction between UA and uricase to yield the blue oxTMB with the peroxidase mimetics activity of CuS NPs, which provided a sensitive and colorimetric method for UA detection with a linear range from 1.0 × 10−6 M to 1.0 × 10−4 M and a detection limit of 1.0 × 10−7 M. Moreover, the proposed method was successfully applied to the determination of UA in human serum samples, which supplied a similar result to the clinical method.

Semiconducting CuO Nanotubes: Synthesis, Characterization, and Bifunctional Photocathodic Enzymatic Bioanalysis.

This work reports the synthesis, characterization, and application of bifunctional semiconducting CuO nanotubes (NTs) electrode for innovative synergized cathodic photoelectrochemical (PEC) enzymatic bioanalysis. Specifically, CuO NTs electrode was fabricated by surface oxidation of the copper foil in an alkaline aqueous solution with (NH4)2S2O8 and then annealed in air at 200 °C. After the subsequent coupling with the model enzyme of xanthine oxidase (XOD), the resulted photocathodic enzyme biosensor exhibited good analytical performance of rapid response, high stability, and good sensitivity. Especially, due to the unique catalytic property of CuO toward H2O2, a novel enzymatic cascade design between biological catalyst (XOD as natural enzyme) and biomimetic catalyst (CuO as the peroxidase mimetics) was constructed, and the dual-catalyst system with special synergy effect could achieve the cathodic PEC guanine bioanalysis with enhanced efficiency. In the determination, the cathodic photocurrent was found to be proportional to the guanine concentration, which was different from the commonly observed O2-dependent suppression of the photocurrent. In all, such a bifunctional CuO NTs-based PEC bioassay format has not been reported. The success of this work can offer great chances for further development and implementation of novel CuO-based PEC bioanalytical systems. More importantly, the strategy proposed here could contribute to the development of an original prototype for general PEC enzymatic bioanalysis.

Hunting for the “Sweet Spot”: Effects of Contiguous Guanines and Strand Lengths on the Catalytic Performance of DNA-Based Peroxidase Mimetics

Hunting for the “Sweet Spot”: Effects of Contiguous Guanines and Strand Lengths on the Catalytic Performance of DNA-Based Peroxidase Mimetics