Salt-template preparation of Mo 5 N 6 nanosheets with peroxidase- and catalase-like activities and application for colorimetric determination of 4-aminophenol

Mo5N6 nanosheets were synthesized by a nickel-induced growth method and were found to possess peroxidase-like activity in acidic condition and catalase-like activity in weak basic condition. In acidic condition, Mo5N6 nanosheets can catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 to form a blue color product (TMBOX). At the co-existence of 4-aminophenol (4-AP), 4-AP can react with H2O2 and TMBOX, resulting in the decrease of TMBOX and the fading of blue color. Therefore, a facile, sensitive colorimetric method for the quantitative detection of 4-AP was developed.
The linear range for 4-AP was 1.0 to 80.0 μmol⋅L‒1 (R2 = 0.999), and the detection limit was 0.56 μmol⋅L‒1 based on 3σ/k. Resorcinol, aniline, humic acid, and common ions and anions in surface water did not interfere the determination of 4-AP. This colorimetric method was applied to measure the 4-AP in real water sample from Wulong River in Fujian Province of China. The relative standard deviation for the determination of 4-AP was ranged from 0.03 to 1.88%, and the recoveries from spiked samples were ranged between 99.2 and 107.6%. The determination results were consistent with those obtained by HPLC.

Catalase-integrated metal-organic framework with synergetic catalytic activity for colorimetric sensing

As a platform for enzyme immobilization, metal-organic frameworks (MOFs) can protect enzyme activity from the interference of external adverse environment. Although these strategies have been proven to produce good results, little consideration has been given to the functional similarity of MOFs to the encapsulated enzyme. Here, catalase (CAT) was encapsulated in Fe-BTC with peroxidase-like activity to obtain a stable composite (CAT@Fe-BTC) with synergistic catalytic activity.
Depending on the superior selectivity and high catalytic activity of CAT@Fe-BTC, colorimetric sensing for the detection of hydrogen peroxide and phenol was developed. This work demonstrates that the integration of functional MOFs with natural enzyme can be well applied to the construction of efficient catalysts.

Cadmium cobaltite nanosheets synthesized in basic deep eutectic solvents with oxidase-like, peroxidase-like, and catalase-like activities and application in the colorimetric assay of glucose.

Cadmium cobaltite (CdCo2O4) nanosheets were ultra-fast synthesized based on a new basic deep eutectic solvent (DES) which served simultaneously as reactant, solvents, and template. Interestingly, the nanosheets were found to exhibit triple-enzyme mimetic activities including oxidase-like activity, peroxidase-like activity, and catalase-like activity. Their catalytic activity followed the typical Michaelis-Menten kinetics, and high affinity for H2O2 and TMB was observed.
Based on the superior peroxidase-like catalytic activity of CdCo2O4 nanosheets, a highly sensitive and selective colorimetric strategy for the determination of glucose was established. Under optimized conditions, the absorbance at 652 nm increases linearly in the 0.5 to 100 μM concentration range, and the limit of detection is 0.13 μM (S/N = 3). Finally, the method was successfully used for determination of glucose in serum samples. Graphical abstract The CdCo2O4 nanosheets were ultra-fast synthesized with a basic deep eutectic solvent, and this nanomaterial exhibited triple-enzyme mimetic activities: oxidase-like activity, peroxidase-like activity, and catalase-like activity. Based on the peroxidase-like activity, a highly sensitive and selective glucose colorimetric sensor was established.

Co3O4 nanocrystals as an efficient catalase mimic for the colorimetric detection of glutathione.

Nanomaterial-based artificial enzymes (nanozymes), as an emerging generation of artificial enzymes, have received extensive attention in recent years owing to their striking merits. In this study, the obtained Co3O4 nanocrystals exhibited catalase-like activity and could catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2, and a clear absorption peak at 652 nm can be observed. It was verified that the catalytic activity for the oxidation of TMB originated from the oxygen, which is generated by Co3O4 catalyzed H2O2 decomposition. Upon addition of glutathione (GSH), the catalytic ability of the Co3O4 nanocrystals was inhibited.
And, the changes of absorbance at 652 nm could be utilized to quantify the concentration of GSH. Under the optimized conditions, the proposed assay showed good linear relationships and a low detection limit towards GSH. Moreover, the Co3O4 nanocrystals had excellent stability and can maintain the catalytic activity for a long time. Thus, a simple, sensitive and selective nanozyme-based biosensor was developed for the colorimetric detection of GSH.

Colorimetric determination of the activities of tyrosinase and catalase via substrate-triggered decomposition of MnO2 nanosheets.

The authors describe novel colorimetric assays for tyrosinase (TYR) and catalase (CAT) based on the substrate-triggered decomposition of MnO2 nanosheets (NSs). The MnO2 NSs can act as oxidase mimics that catalyze the oxidation of the substrate tetramethylbenzidine (TMB) to form a blue dye with an absorption maximum at 652 nm. The oxidase-mimicking activity of the MnO2 NSs is inhibited by dopamine (DA)/hydrogen peroxide (H2O2) due to their decomposition of the MnO2 NSs. TYR catalyzes the oxidation of DA while CAT can decompose H2O2 into water and oxygen.
Therefore, the oxidase-mimicking activity of MnO2 NSs is restored in the presence of both enzymes and their substrates. Based on the competitive consumption of substrates between enzymes and MnO2 NSs, a colorimetric method for determination of enzyme activity and its substrate is developed. The detection limits for TYR and CAT are 6 mU·mL-1 and 33 mU·mL-1, respectively. Graphical abstractA colorimetric method for monitoring enzyme activity and its substrate is described. It is based on the substrate-inhibited oxidase-mimicking activity of MnO2 nanosheets.

Catalase (CAT) Colorimetric Assay Kit

MBS2556989-48Test MyBiosource 48Test 230 EUR

Catalase (CAT) Colorimetric Assay Kit

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Catalase (CAT) Colorimetric Assay Kit

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Catalase (CAT) Colorimetric Assay Kit

MBS2556989-96Tests MyBiosource 96Tests 250 EUR

Catalase Colorimetric Activity Kit (2 Plate)

K033-H1 Arbor Assays 2 x 96 well plate 425 EUR

OKAU00112-2PLATE - Catalase Colorimetric Activity Kit

OKAU00112-2PLATE Aviva Systems Biology 2plate 379 EUR

Catalase Activity Colorimetric/Fluorometric Assay Kit

K2177-100 ApexBio 100 assays 427 EUR

Catalase Activity Colorimetric/Fluorometric Assay Kit

K773-100 Biovision each 502.8 EUR

OxiSelect™ Catalase Activity Assay Kit (Colorimetric)

STA-341 Cell Biolabs 96 assays 595 EUR

OxiSelect Catalase Activity Assay Kit (Colorimetric), Trial Size

STA-341-T Cell Biolabs 20 assays 435.6 EUR

Cathepsin G Substrate, Colorimetric

2206-25 Biovision each 360 EUR

Cathepsin G Substrate, Colorimetric

2206-5 Biovision each 138 EUR

Urea Colorimetric Assay

TBS2201 Tribioscience 500 tests 259 EUR

Boron Colorimetric Assay

TBS2301-200 Tribioscience 200 tests 360 EUR

Colorimetric Substrate, 5ML

C129-5ML Arbor Assays 5ML 254 EUR

HRP Colorimetric Substrate

79651 BPS Bioscience 10 ml 105 EUR

HDAC Substrate, Colorimetric

2207-100 Biovision each 360 EUR

HDAC Substrate, Colorimetric

2207-25 Biovision each 151.2 EUR

Tyrosine Colorimetric Assay

TBS2070-100 Tribioscience 100 tests 429 EUR

Colorimetric aminotriazole assay based on catalase deactivation-dependent longitudinal etching of gold nanorods.

A colorimetric and visual assay is described for the herbicide aminotriazole (ATZ). It is based on the etching of gold nanorods (AuNRs) by iodine which is formed on oxidation of iodide via H2O2. Longitudinal etching of the AuNRs occurs quickly and is accompanied by a color change from dark blue to red. In the absence of ATZ and the presence of active catalase (CAT), H2O2 is quickly decomposed into water, and the AuNRs will not be etched. In the presence of ATZ, CAT is partially deactivated, and this affects the amount of available H2O2 and, consequently, of the iodine. Hence, the color is significantly changed.
The color changes can be easily detected with bare eyes. The assay has a linear response in the 5 to 70 μM concentration range, with a detection limit of 1.3 μM and high selectivity for ATZ. It was applied to the determination of ATZ in water and food samples. Graphical abstract A multicolor colorimetric method is developed for aminotriazole (ATZ) detection based on catalase (CAT) deactivation-dependent longitudinal etching of gold nanorods (AuNRs). The color signals can be visually identified. Good detection performances and capability for evaluating ATZ level in water and food samples is demonstrated.

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