The Oxidation Of 3,3,5,5-tetramethylbenzidine Research Articles

A novel three-stage continuous sensing platform for H2O2 and cholesterol based on CuFeS2 nanozyme: Theoretical calculation and experimental verification

It is still a challenge to establish a facile and reliable sensing platform with broad linear range. In this work, an innovative substrate concentration-regulated strategy was developed for design of three-stage continuous colorimetric sensing platform for H2O2, vastly broadening the detecting linear range of the sensor. In detail, a novel nanozymes, the hollow CuFeS2 nanospheres with excellent peroxidase-like activity was synthesized, which could catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by H2O2. Cytotoxicity test toward HUVEC and Hela cells verified the good biocompatibility of CuFeS2, guaranteeing its safety in biological applications. DFT theoretical calculation and experimental results both proved that the H2O2 adsorption capacity of CuFeS2 was higher than that of CuS and FeS. On this basis, a three-stage continuous sensing platform with broad detecting range by adjusting the concentration of TMB was developed. The proposed method was also successfully applied in detecting H2O2 in milk samples. Besides, coupled with cholesterol oxidase (ChOx), a cascade catalyzed colorimetric sensing platform for determining cholesterol had been constructed. Thus, this work not only provides the excellent performance of nanozymes, but also opens up a new avenue for designing sensing platform with extra-wide detecting range.

Hydrogel-involved portable colorimetric sensor based on oxidase mimic Fe/Co-NC for acetylcholinesterase detection and pesticides inhibition assessment

Herein, we synthesized a novel N-doped carbon layer encapsulated Fe/Co bimetallic nanoparticles (Fe/Co-NC), which exhibited superior oxidase-like activity due to the facilitation of electron penetration and the formation of metal-nitrogen active sites. Fe/Co-NC could catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) to blue oxTMB. Acetylcholinesterase (AChE) could catalyze the hydrolysis of thioacetylcholine to produce reducing thiocholine, which prevented TMB from oxidation. Thus, a portable hydrogel colorimetric sensor was developed for on-site and visual monitoring of AChE with the detection limit of 0.36 U L−1, and successfully applied to detect AChE in human erythrocyte samples. Furthermore, this platform was used to investigate the inhibition of triazophos on AChE activity.

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.

Nitrogen-doped porous carbon nanomaterials synthesized using a magadiite template as efficient peroxidase mimics for colorimetric detection of ascorbic acid as an antioxidant.

Nanomaterials with intrinsic enzyme-like activity have gained substantial scientific attention as viable substitutes to natural biological enzymes owing to their cheap price and great stability. Numerous artificial enzyme mimics have been employed effectively in sectors such as sensing, environmental processing, and cancer treatment. In this study, novel nitrogen-doped porous carbon nanomaterials (CPs) were produced by modifying polypyrrole with magadiite using chemical oxidative polymerization and calcination methods. The obtained nitrogen-doped porous carbon nanomaterials exhibited improved peroxidase-like activity, which catalyzed the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2) to produce colorful compounds. Kinetic investigation revealed that the affinity for TMB of nitrogen-doped porous carbon peroxidase mimics was higher than that of genuine horseradish peroxidase (HRP). In addition, a sensitive assay with encouraging performance for the colorimetric detection of ascorbic acid (AA) was successfully fabricated employing nitrogen-doped porous carbon nanomaterials as peroxidase mimics. The results were satisfactory and demonstrated its potential application in antioxidant detection.

MXene catalytic amplification-fluorescence/absorption dimode aptamer sensor for the detection of trace Pb2+ in milk.

Lead ion (Pb2+) is a toxic heavy metal, which is very harmful to organisms. Therefore, the establishment of a rapid, simple, and sensitive method is of great significance to food safety and human health. It was found that MXeneTi3C2 nanosheet (NS) has a strong catalytic effect on the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) via H2O2 to form the oxidized product (TMBOX); it has a strong fluorescence peak at 415 nm and an absorption (Abs) peak at 295 nm. The aptamer of Pb2+ (Aptpb) can be adsorbed on the surface of an NS to form MXene-Apt conjugates, which reduces its catalytic active sites and inhibits its catalytic activity. When the target Pb2+ is added, it specifically binds with Aptpb to release MXene NSs to enhance the dimode signals. Therefore, a new MXene catalytic fluorescence/absorption dimode aptamer biosenering platform was fabricated for the determination of trace Pb2+ in milk and water samples, with the fluorescence assay linear range (LR) of 5.0 × 10-2-2.0 nmol/L.

Synthesis of a cerium-based nanomaterial with superior oxidase-like activity for colorimetric determination of glutathione in food samples.

Enzyme-like nanomaterials have received significant attention for their high stability and low cost. However, most nanomaterials require complicated synthesis processes, limiting the range of their potential applications. In this study, a novel cerium-based nanomaterial was fabricated in a facile manner from a mixture of dipicolinic acid (DPA), guanosine 5'-monophosphate (GMP), and cerium acetate under ambient conditions. The obtained nanomaterial, designated as DPA-Ce-GMP, exhibited superior oxidase-like activity owing to the mixed valence (Ce3+/Ce4+) of cerium ions. DPA-Ce-GMP efficiently catalyzed the oxidation of 3,3,5,5-tetramethylbenzidine (TMB), achieving a color reaction without requiring hydrogen peroxide. Thus, DPA-Ce-GMP was incorporated into a simple, rapid, and sensitive colorimetric sensor for glutathione (GSH) detection. Within this sensor, TMB oxidation is inhibited by the reducibility of GSH. The sensor exhibits a linear response over two concentration ranges (0.05-10 and 10-40μM), and its detection limit is 17.1nM (3σ/slope). The proposed sensor was successfully applied to GSH quantification in food samples. The developed sensor provides an efficient biomimic oxidase for GSH detection in real samples. Facile approach to prepare cerium-based nanomaterial with superior oxidase-like activity for colorimetric detection of glutathione in food samples.

Palygorskite@Co3O4 nanocomposites as efficient peroxidase mimics for colorimetric detection of H2O2 and ascorbic acid

Nanomaterials with intrinsic enzyme-like activities have attracted extensive research interest as promising alternatives to natural biological enzymes due to their advantages of low cost and high stability. Many artificial enzyme mimics have been successfully applied in the fields of sensing, environmental treatment, and oncotherapy. Herein, novel palygorskite@Co3O4 nanocomposites (Pal@Co3O4 NCs) were fabricated by modifying Pal with Co3O4 nanoparticles through a facile hydrothermal method. The obtained Pal@Co3O4 nanocomposites as nanozymes displayed enhanced peroxidase-like activity, which can catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2) to obtain colored products. Kinetic assay indicated that the Pal@Co3O4 peroxidase mimics showed a higher affinity towards TMB than that of natural horseradish peroxidase (HRP). Moreover, a sensitive and selective sensor for colorimetric determination of H2O2 and ascorbic acid (AA) was successfully constructed by using Pal@Co3O4 nanocomposites as peroxidase mimics. Furthermore, the proposed assay for sensing of AA in model samples was evaluated with satisfactory results, demonstrating the potential applications in complex biological systems.

A colorimetric sensing strategy based on enzyme@metal-organic framework and oxidase-like IrO2/MnO2 nanocomposite for α-glucosidase inhibitor screening.

A highly sensitive colorimetric sensing strategy based on enzyme@metal-organic framework (GAA@Cu-MOF) and IrO2/MnO2 nanocomposite was exploited innovatively for screening of α-glucosidase (GAA) inhibitors. IrO2/MnO2 nanocomposite exhibits excellent oxidase-mimicking activity which can directly catalyze the oxidation of 3,3,5,5,-tetramethylbenzidine (TMB) into a blue product with an absorption maximum at 652nm. And GAA@Cu-MOF can decompose L-ascorbic acid-2-O-α-D-glucopyranosyl (AAG) to ascorbic acid (AA). The produced AA can destroy the IrO2/MnO2 nanocomposite and reduce its oxidase-like activity. However, the generation of AA is restricted when GAA inhibitors are added to the system, which allows the oxidase-like activity of the IrO2/MnO2 nanocomposite to be maintained. In view of this, a method for screening of GAA inhibitors was developed. In addition to enhancing the stability of GAA, the method can also effectively avoid the potential interference of H2O2 in the screening process of GAA inhibitors, which helps to improve the sensitivity of the method. Therefore, highly sensitive determination for acarbose and ascorbic acid are achievedwith detection limits of 6.27nM and 1.23μM, respectively. The proposed method was successfully applied to screen potential GAA inhibitors from oleanolic acid derivatives. Graphical abstract.

Nitrogen- and sulfur-doped carbon dots as peroxidase mimetics: colorimetric determination of hydrogen peroxide and glutathione, and fluorimetric determination of lead(II).

Fluorescent carbon dots co-doped with nitrogen and sulfur (N/S CDs) were prepared and found to display viable peroxidase mimicking activity. They have a blue fluorescence (with excitation/emission maxima at 340/456nm) with a quantum yield of 35%. The N/S CDs catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H2O2, and this leads to the appearance of a blue solution with a absorption maximum at 654nm. A colorimetric method was developed for the determination of H2O2 that has a 1.75μM detection limit and a linear response in the 10-5 to 10-4M concentration range. The method can be extended to the enzymatic determination of glutathione with a 0.26μM detection limit and a working rangefrom 0.20 to 100μM. In addition, the CDs respond to lead(II) which is a quencher of the blue fluorescence at 456nm, with a detectionlimit of 11μM and a working range up to 100μM. Simultaneously, the color changes can be visually detected with absorbance signal changes from 10 to 100μM with limit of 3.9μM. A multiple detection system was worked out that allows monitoring of H2O2 and glutathione successively, and of lead(II). Graphical abstract (A) Schematic representation of the nitrogen & sulphur doped carbon dots with blue fluorescence, (B) the peroxidase-like activity in colorimetric detecting of H2O2 and GSH and (C) the illustration for the application of Pb2+ detection with fluorescence and colorimetric method.

Colorimetric determination of ascorbic acid and the activity of alkaline phosphatase based on the inhibition of the peroxidase-like activity of citric acid-capped Prussian Blue nanocubes.

Colorimetric methods are described for the determination of ascorbic acid (AA) and alkaline phosphatase (ALP). Both assays are based on the inhibition of the peroxidase (POx)-like activity of Prussian Blue nanocubes (PB NCs) capped with citric acid. They catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by H2O2 to produce a blue color with an absorption maximum at 652nm. On addition of AA, the PB NCs are reduced to Prussian White (PW) which does not act as a POx mimic. This results in a decreased rate of the formation of the blue coloration whose intensity decreases with increasing concentration of AA. The assay allows AA to be quantified with a 35nM detection limit (at 3σ/m). The hydrolysis of AA phosphate by ALP leads to the formation of AA which can be quantified by the above method. Based on this, the activity of ALP can be determined by measurement of the intensity of the blue coloration thus formed. The method can be used to determine the activity of ALP with a detection limit as low as 0.23U·L-1. Graphical abstract Schematic presentation of a method forcolorimetric determination of ALP activity. AA obtained by ALP-catalyzed hydrolysis of ascorbic acid phosphate (AAP) inhibits the intrinsic peroxidase-like activity of PB NCs by reducing Prussian Blue nanocrystals(PB NCs) to form inactive Prussian White (PW).

Germanium nanoparticles: Intrinsic peroxidase-like catalytic activity and its biosensing application

In recent years, germanium nanoparticles (Ge NPs) have attracted considerable research attention because of its excellent electrical and optical properties. However, it is mainly applied in the field of solar cells, photodetectors and photothermal therapy. Actually, Ge NPs have the advantages of low toxicity and excellent biocompatibility, which means that they have great potential in biosensing applications. However, there are few related reports. In this paper, we discovered that Ge NPs have the intrinsic peroxidase-like catalytic activity and can significantly accelerate the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by H2O2 for the first time. Compared with natural enzyme (horseradish peroxidase, HRP), Ge NPs maintain higher catalytic stability after treatment at different pH, temperature and ionic strength. Furthermore, a Ge NPs-based colorimetric platform was established for the first time to detect biomolecules with favourable sensitivity and selectivity, such as uric acid, glucose and choline. This work finds the new property of Ge NPs and extends its application in biosensing.

A bimetallic (Co/2Fe) metal-organic framework with oxidase and peroxidase mimicking activity for colorimetric detection of hydrogen peroxide

A bimetallic metal-organic framework of the type MOF(Co/2Fe), synthesized by a hydrothermal method, is demonstrated to exhibit peroxidase-like activity and oxidase-like activity. The material catalyzes the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) to produce a blue product both in the absence and presence of H2O2. Its catalytic activity strongly depends on temperature and the solution pH value. With its dual enzyme mimetic activity, MOF(Co/2Fe) has the advantages of low cost, good stability, ease of preparation, and attractive Michaelis-Menten behavior. The mechanisms and kinetics of the pseudo-enzymatic activity were studied in some detail. A colorimetric method was developed for determination of H2O2 that is based on the peroxidase-like activity of MOF(Co/2Fe). Under the optimal conditions, the absorbance of oxidized TMB at 652 nm increases linearly in the 10 to 100 μM H2O2 concentration range, with a 5 μM limit of detection.

Ultrasmall Pt Nanoclusters as Robust Peroxidase Mimics for Colorimetric Detection of Glucose in Human Serum.

In this work, a new type of ultrasmall Pt nanoclusters (Pt NCs) was prepared via a facile one-pot approach by using yeast extract as the reductant and stabilizer. Besides their excellent water solubility, these yeast extract-stabilized Pt NCs also possess attractive peroxidase mimicking property. They can efficiently catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the coexistence of hydrogen peroxide (H2O2). Catalytic mechanism analysis suggested that the peroxidase mimicking activity of these Pt NCs might originate from their characteristic of accelerating electron transfer between TMB and H2O2, and their enzymatic kinetics followed typical Michaelis-Menten theory. On the basis of these findings, we developed a new highly sensitive colorimetric method for glucose detection, and the limit of detection was calculated as low as 0.28 μM (S/N = 3). Further application of the present system for glucose detection in human serum has been successfully demonstrated, suggesting its promising utilization as robust peroxidase mimics in the clinical diagnosis, pharmaceutical, and environmental chemistry fields.

SDS–MoS2 nanoparticles as highly-efficient peroxidase mimetics for colorimetric detection of H2O2 and glucose

In this work, we find that the peroxidase-like activity of MoS2 nanoparticles (NPs) is dependent on the surface charge. Negatively charged sodium dodecyl sulfate modified MoS2 nanoparticles (SDS–MoS2 NPs) possess highly-efficient peroxidase-like activity. MoS2 NPs with intrinsic peroxidase-like activity were synthesized through a simple one-pot hydrothermal route. The peroxidase-like activities of different surfactants modified MoS2 NPs were discussed. Compared with bare MoS2 NPs and positively charged cetyltrimethyl ammonium bromide modified MoS2 NPs, SDS–MoS2 NPs have the best peroxidase-like activity. SDS–MoS2 NPs can efficiently catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H2O2 to generate a blue product. On basis of this, we have successfully established a novel platform for colorimetric detection of H2O2, and the detection limit is 0.32μM. Furthermore, the SDS–MoS2 NPs based platform can also be used for high sensitivity and selectivity detection of glucose with a wide linear range of 5.0–500μM by controlling the generation of H2O2 in the presence of glucose oxidase.

Intrinsic peroxidase-like activity exhibited by cerium oxide nanoparticles and their application to glucose detection

In this paper, the stable and good water-soluble polyacrylic acid functioned cerium oxide nanoparticles (CeO2 NPs) were successfully synthesized and characterized by dynamic light scattering (DLS), FT-IR and XPS. The experimental results indicated that the prepared CeO2 NPs exhibit intrinsic peroxidase-like activity, which can catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H2O2 to produce blue reaction. Electron paramagnetic resonance (EPR) and Raman techniques were used to investigate the catalytic mechanism. On the basis of H2O2 concentration-dependent peroxidase-like activity of CeO2 NPs, a simple, low cost and selectively colorimetric method was constructed for sensing of glucose. Under the optimal conditions, the linear range for the determination of glucose was 0.5-10 mmol/L with a limit of detection (LOD, 3 σ ) of 0.1 mmol/L. The RSD was 2.4% for 1.0 mmol/L glucose ( n = 11). The proposed method has been successfully used for determination of glucose in serum samples.

Fe(iii)-based coordination polymernanoparticles: peroxidase-like catalytic activity and their application to hydrogen peroxide and glucose detection

Fe(III)-based coordination polymer nanoparticles (FeCPNPs) have been prepared for the first time by simple mixing of ferric chloride and sodium hexametaphosphate (SHAM) aqueous solutions at room temperature. It was found that such FeCPNPs possess peroxidase-like activity capable of catalyzing the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by H2O2 turning the solution blue in color. Based on these findings, a simple, sensitive and selective colorimetric assay to detect H2O2 was developed, with the linear range and detection limit estimated to be from 1 μM to 50 μM (r = 0.997) and 0.4 μM, respectively. The application of this colorimetric assay to glucose detection both in buffer solution and diluted serum has also been demonstrated successfully. This glucose sensor exhibits excellent performance with a linear range from 2 μM to 20 μM (r = 0.985) and a detection limit of about 1 μM.