ascorbic-acid and 3-3--5-5--tetramethylbenzidine

A fluorescence and photothermal dual-signal assay was developed for the determination of ascorbic acid (AA). Cerium/polyacrylic acid modified porphyrin metal-organic frameworks (PCN-224@PAA-Ce MOFs) exhibit oxidase-like activity and can effectively oxidize 3,3 ', 5,5 '-tetramethylbenzidine (TMB) from colorless substrates to blue substrates (oxTMB). The absorption spectrum of oxTMB overlaps with the emission spectrum of PCN-224@PAA-Ce, resulting in quenching of fluorescence emission of PCN-224@PAA-Ce. oxTMB, as an excellent photothermal agent, converts the optical signal into the thermal signal (temperature increasing) driven by 808 nm laser. In the presence of AA, the blue oxTMB was reduced to colorless TMB, which led to the fluorescence recovery of PCN-224@PAA-Ce and at the same time, the photothermal signal was changed with the temperature decreasing under the driving of 808 nm laser. The detection limits (LOD) of fluorescence/photothermal dual-mode AA sensor strategies were as low as 0.73 μM and 1.4 μM, respectively. Rapid analysis of ascorbic acid was accomplished with the present procedure, AA in vitamin C tablets and human serum samples were validated.

Topics: Ascorbic Acid; Cerium; Colorimetry; Humans; Limit of Detection; Metal-Organic Frameworks; Porphyrins

Topics: Ascorbic Acid; Cobalt; Colorimetry; Metal-Organic Frameworks; Nickel; Oxidoreductases

Mn

Topics: Ascorbic Acid; Colorimetry; Hydrogen Peroxide; Nanoparticles; Oxidoreductases; Porosity; Reproducibility of Results

Glutathione (GSH) is the most abundant low-molecular-weight biological thiol in vivo and has been linked to several diseases. The accurate quantification of GSH is therefore crucial for disease diagnosis and monitoring. In this study, we prepared self-assembled Cu(I)-Cys (cysteine) nanozymes through a two-step procedure. The Cu(I)-Cys nanoparticles exhibited peroxidase-mimicking activity. Upon the addition of H

Topics: Ascorbic Acid; Cysteine; Glutathione; Humans; Hydrogen Peroxide; Peroxidases

Topics: Alkaline Phosphatase; Ascorbic Acid; Benzidines; Cerium; Colorimetry; Coloring Agents; Immunoassay; Ions; Limit of Detection; Ochratoxins

It has been well known that metallic nanoparticles with striking properties possess wide application prospects in the processes of colorimetric detection, catalysis, disease diagnosis and treatment, energy, wastewater treatment, remediation, and antibacterial activity in recent years. Herein, iron-based nanoparticles (FeNPs), metallic nanoparticles, were synthesized via a facile chemical reduction method using a hyperaccumulator plant. Also, their use in antibacterial activity applications and colorimetric ascorbic acid (AA) detection was investigated. It was observed that FeNPs presented high antibacterial potency against Gram-positive bacteria of

Topics: Anti-Bacterial Agents; Ascorbic Acid; Colorimetry; Escherichia coli; Hydrogen Peroxide; Iron; Magnetic Phenomena; Metal Nanoparticles; Pinus

A two-dimensional (2D) Co-MOF nanosheet-based nanozyme was developed for colorimetric detection of disease-related biomolecules. The prepared 2D Co-MOFs exhibited ultrahigh peroxidase catalytic activity. 2D Co-MOFs can catalyze the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to the blue product oxTMB, accompanying an obvious change of absorption value at 652 nm. However, alkaline phosphatase can catalyze the hydrolysis of L-ascorbic acid-2-phosphate to produce ascorbic acid which can reduce the oxTMB to TMB, resulting in an obvious color fading. Therefore, by recording the change of absorption value at 652 nm, the 2D Co-MOF nanosheets were used to detect ascorbic acid (AA) and alkaline phosphatase (ALP). The limit of detection for AA and ALP was 0.47 μM and 0.33 U L

Topics: Alkaline Phosphatase; Ascorbic Acid; Benzidines; Catalysis; Chromogenic Compounds; Cobalt; Colorimetry; Humans; Limit of Detection; Metal-Organic Frameworks; Nanostructures; Oxidation-Reduction; Paper; Smartphone

Topics: Acid Phosphatase; Ascorbic Acid; Benzidines; Chlorides; Chromogenic Compounds; Colorimetry; Fluorescent Dyes; Gold Compounds; Humans; Limit of Detection; Oxidation-Reduction; Rhodamines; Smartphone; Spectrometry, Fluorescence

As a powerful tool for medical diagnosis and bioanalysis, conventional optical spectrometers are generally expensive, bulky and always require an accompanying data processing device. In this work, we developed a novel smartphone-based CD-spectrometer (SCDS) for high sensitive and ultra-portable colorimetric analysis, with the advantage of cost-effective and simplicity. The distance between the light source and slit, the structure of SCDS and the parameters of camera in the smartphone were all optimized to ensure the best analytical performance. Besides, the SCDS employed HSV color model and utilized the overall intensity calculated by summing V-value of adjacent position for the absorbance measurement. In this way the errors caused by the low resolution of CD-grating can effectively be eliminated to promote the sensitivity of the SCDS. The performance of the SCDS was first validated for colorimetric detection of BSA with a detection limit of 0.0073 mg/mL, which is superior compared to that of the microtiter plate reader (MTPR). Moreover, by combining with 3,3',5,5'-tetramethylbenzidine-manganese dioxide (TMB-MnO

Topics: Animals; Ascorbic Acid; Benzidines; Beverages; Cattle; Colorimetry; Compact Disks; Equipment Design; Limit of Detection; Manganese Compounds; Nanostructures; Oxides; Point-of-Care Testing; Serum Albumin, Bovine; Smartphone; Spectrum Analysis

Topics: Acid Phosphatase; Ascorbic Acid; Benzidines; Energy Transfer; Gold; Metal Nanoparticles; Particle Size; Platinum; Surface Plasmon Resonance; Surface Properties

Core-shell palladium cube@CeO

Topics: Alkaline Phosphatase; Ascorbic Acid; Benzidines; Catalysis; Cerium; Colorimetry; Coloring Agents; Enzyme Assays; Limit of Detection; Metal Nanoparticles; Oxidation-Reduction; Palladium

There is an ongoing need to develop high-performance sensing strategy for detecting and discriminating antioxidants, primarily because of their role in medical diagnosis and food. In this regard, visual sensor arrays have been a subject of intensive research for such applications. To this end, we propose a colorimetric sensor array for accurate detection and identification of antioxidants, which is based on the reactions between 3,3',5,5'-tetramethylbenzidine (TMB) and metal ions as sensing receptors and the interactions between antioxidants and oxidized TMB (oxTMB). Different target antioxidants displayed diverse reduction abilities toward the oxTMB, creating distinct colorimetric response patterns. The combination of colorimetric response variation at color and absorbance at 652 nm enables the sensor array to provide a unique fingerprint pattern to each antioxidant. Linear discriminant analysis (LDA) and centroid diagrams show that the sensor array can well detect and discriminate the eight tested antioxidants, including lipoic acid (LIA), cysteine (Cys), tannin (TA), ascorbic acid (AA), glutathione (GSH), Uric Acid (UA), glycine (Gly), and dopamine (DA), with a high sensitivity in the range of nanomolar concentrations.

Topics: Antioxidants; Ascorbic Acid; Benzidines; Biosensing Techniques; Colorimetry; Cysteine; Dopamine; Glutathione; Glycine; Ions; Metals, Heavy; Particle Size; Surface Properties; Tannins; Thioctic Acid; Uric Acid

A turn-on method for determining α-glucosidase activity is described using a chemical redox strategy in which the fluorescence of red fluorescent carbon dots (CDs) is modulated. The red fluorescent CDs were prepared using a solvothermal method with p-phenylenediamine and sodium citrate. The excitation and emission maxima of the CDs were 490 and 618 nm, respectively. Ce

Topics: alpha-Glucosidases; Ascorbic Acid; Benzidines; Carbon; Cerium; Chromogenic Compounds; Color; Enzyme Assays; Fluorescence; Fluorescent Dyes; Humans; Limit of Detection; Oxidation-Reduction; Quantum Dots; Spectrometry, Fluorescence

A colorimetric assay is presented for the determination of ascorbic acid (AA). Manganese(II) doped carbon dots (Mn-CDs) were prepared by a convenient hydrothermal route and are shown to possess oxidase-like catalytic ability. They catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by dissolved oxygen to form a blue colored product (oxTMB). AA can reduce blue oxTMB to colorless TMB. The fading of the blue color (measured at 652 nm) can be applied for quantifying AA in the 50 to 2500 nM concentration range and with a 9 nM detection limit. The method was successfully used for the quantitation of AA in real samples. Graphical abstract Schematic representation of a colorimetric assay platform for the sensitive detection of ascorbic acid (AA) in view of inhibitory effect of AA on the 3,3',5,5'-tetramethylbenzidine (TMB) oxidation, benefitting from excellent oxidase-like catalytic activity of manganese(II) doped carbon dots (Mn-CDs).

Topics: Ascorbic Acid; Benzidines; Carbon; Catalysis; Citrus sinensis; Colorimetry; Coloring Agents; Fruit and Vegetable Juices; Humans; Limit of Detection; Manganese; Oxidation-Reduction; Oxidoreductases; Quantum Dots; Tablets

A sensitive colorimetric method is described for the determination of the activity of alkaline phosphatase (ALP). It is based on the regulation of the oxidase-mimicking activity of MnO

Topics: Alkaline Phosphatase; Animals; Ascorbic Acid; Benzidines; Biomimetic Materials; Catalysis; Cattle; Colorimetry; Coloring Agents; Limit of Detection; Manganese Compounds; Nanostructures; Oxidation-Reduction; Oxides; Oxidoreductases; Oxygen

An 'turn-off' approach for the detection of ascorbic acid (AA) using 3,3',5,5',-tetramethylbenzidine (TMB) as a colorimetric probe is developed. The proposed method is based on the fact that hypochlorite (ClO

Topics: Ascorbic Acid; Benzidines; Biosensing Techniques; Colorimetry; Humans; Hypochlorous Acid; Limit of Detection; Linear Models; Reproducibility of Results

Natural enzyme mimetics with high catalytic activity at nearly neutral pH values are highly desired for their applications in biological systems. Herein for the first time a stable MOF, namely MOF-808, has been shown to possess high intrinsic peroxidase-like catalytic activity under acidic, neutral, and alkaline conditions. As a novel peroxidase mimetic, MOF-808 can effectively catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine when H

Topics: Ascorbic Acid; Benzidines; Biomimetic Materials; Biosensing Techniques; Catalysis; Colorimetry; Glucose; Hydrogen Peroxide; Hydrogen-Ion Concentration; Kinetics; Limit of Detection; Metal-Organic Frameworks; Oxidation-Reduction; Peroxidases

Here we report a unique visual colorimetric sensor array for discrimination of antioxidants in serum based on MnO

Topics: Animals; Antioxidants; Ascorbic Acid; Benzidines; Biosensing Techniques; Cattle; Chromogenic Compounds; Colorimetry; Cysteine; Glutathione; Manganese Compounds; Melatonin; Nanostructures; Oxides; Serum; Uric Acid

An ultrasensitive non-enzymatic electrochemical carcinoembryonic antigen (CEA) immunosensor was fabricated by the immobilization of a monoclonal CEA antibody (anti-CEA) on a protein A (PA) attached-gold nanoparticles (AuNPs)-deposited electrochemically prepared polydopamine film (e-PD/AuNPs). Magnetic beads (MB)-supported and CEA-conjugated multiple 3,3',5,5'-tetramethylbenzidine (TMB) was used as electrochemical labels. The detection was based on the measurements of the electrocatalyzed oxidation of ascorbic acid (AA) by the multiple TMB labels after competitive binding between MB/TMB-conjugated-CEA and free-CEA. The electrocatalyzed oxidation current of AA by TMB decreased with increasing concentration of the free-CEA as the amount of CEA/MB/TMB labels decreased at the immunosensor probe. The immunosensor surface was characterized using electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy, quartz crystal microbalance, and scanning electron microscopy techniques. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques were used to monitor the electrocatalyzed response. The proposed immunosensor exhibited a wide linear dynamic range (1.0 pg/mL to 10.0 ng/mL), low detection limit (1.0±0.04 pg/mL), good selectivity, and long-time stability. It was successfully applied to various CEA spiked human serum samples for the detection of CEA.

Topics: Antibodies, Immobilized; Ascorbic Acid; Benzidines; Biosensing Techniques; Carcinoembryonic Antigen; Electrochemical Techniques; Gold; Humans; Immunoassay; Indoles; Limit of Detection; Magnets; Metal Nanoparticles; Oxidation-Reduction; Polymers

The application of a novel assay for the direct measurement of prooxidant-antioxidant balance (PAB) in type II diabetes and the evaluation of antioxidant therapy.. The assay is based on 3,3',5,5'-tetramethylbenzidine and its cation, used as a redox indicator participating in two simultaneous reactions. PAB was determined in the sera of healthy volunteers and type II diabetes patients. The results were compared with clinical and biological parameters, protein oxidation markers, as well as the results of antioxidant and prooxidant assays. PAB, after administration of vitamins C and E for 1 day, 1 month and 2 months was also determined.. Increased PAB was found in the patients' group and correlated with parameters involved in diabetic complications, protein oxidation markers, antioxidant and prooxidant assays. One day after vitamin administration, a significant shift of PAB towards antioxidants was observed. PAB remained unchanged after 1 month and changed marginally in favor of prooxidants in the second month of the therapy.. These results indicate that the measurement of PAB may be useful to identify and follow-up patients who need antioxidant therapy.

Topics: Adult; Aged; Antioxidants; Ascorbic Acid; Benzidines; Chromogenic Compounds; Clinical Laboratory Techniques; Diabetes Mellitus, Type 2; Female; Humans; Male; Middle Aged; Oxidants; Sensitivity and Specificity; Vitamin A

Human thyroid peroxidase (hTPO) catalyzes a one-electron oxidation of benzidine derivatives by hydrogen peroxide through classical Chance mechanism. The complete reduction of peroxidase oxidation products by ascorbic acid with the regeneration of primary aminobiphenyls was observed only in the case of 3,3',5,5'-tetramethylbenzidine (TMB). The kinetic characteristics (k(cat) and K(m)) of benzidine (BD), 3,3'-dimethylbenzidine (o-tolidine), 3,3'-dimethoxybenzidine (o-dianisidine), and TMB oxidation at 25 degrees C in 0.05 M phosphate-citrate buffer, pH 5.5, catalyzed by hTPO and horseradish peroxidase (HPR) were determined. The effective K(m) values for aminobiphenyls oxidation by both peroxidases raise with the increase of number of methyl and methoxy substituents in the benzidine molecule. Efficiency of aminobiphenyls oxidation catalyzed by either hTPO or HRP increases with the number of substituents in 3, 3', 5, and 5' positions of the benzidine molecule, which is in accordance with redox potential values for the substrates studied. The efficiency of HRP in the oxidation of benzidine derivatives expressed as k(cat)/K(m) was about two orders of magnitude higher as compared with hTPO. Straight correlation between the carcinogenicity of aminobiphenyls and genotoxicity of their peroxidation products was shown by the electrophoresis detecting the formation of covalent DNA cross-linking.

Topics: Aminobiphenyl Compounds; Ascorbic Acid; Benzidines; Dianisidine; DNA; DNA Damage; Humans; Hydrogen-Ion Concentration; Iodide Peroxidase; Kinetics; Oxidation-Reduction

An extraction test for stool occult blood was developed using 3,3', 5,5' tetramethylbenzidine (TMB), which gave reliable results in the presence of interfering substances, such as vitamin C, meat fibers, and vegetable enzymes. The new test was applied to 1,320 fecal specimens from hospitalized patients not on dietary restrictions. Of 189 specimens unequivocally positive by slide tests, 48 were negative by the extraction test, 42 were trace reactions, and 99 were 2+ to 4+. Extraction testing was performed on 351 of the 1,082 specimens negative by slide tests. Four of these were from patients taking supplemental vitamin C. Two of these specimens were extraction test positive ( ) and two were extraction test negative. One other specimen, from a patient not on supplemental vitamin C, was extraction test positive. Forty-nine specimens gave equivocal results, with two commercial slide tests for occult blood. By the extraction test, 26 of these were negative, 13 had trace amounts of blood, and 10 were 2+ or 4+.

Topics: Ascorbic Acid; Benzidines; Chromogenic Compounds; Diet Therapy; Humans; Occult Blood; Reference Standards