ascorbic-acid and manganese-dioxide

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

The detection of enzyme activity can provide valuable insights into clinical diagnosis. Herein, we synthesize gold nanobipyramids@MnO2 nanoparticles (AMNS) as the surface-enhanced Raman spectroscopy (SERS) substrate for the first time and design a "turn-on" SERS strategy for the detection of enzyme activity without the need for a complicated SERS nanotag preparation process. In the presence of alkaline phosphatase (ALP), 2-phosphate-l-ascorbic acid trisodium salt (AAP) can be hydrolyzed to ascorbic acid (AA), which can etch the shell of AMNS by reducing MnO2 to Mn2+. The cracked MnO2 shell-caused electromagnetic field enhancement from AMNS can give rise to a significant increase in the Raman intensity of the adsorbed molecules (i.e., crystal violet, CV) on the surfaces of nanobipyramids. Thus, the ALP activity can be accurately quantified based on the MnO2 shell thickness dependent Raman signal output from CV. A linear dynamic range from 0.4 to 20 mU mL-1 with a detection limit of 0.04 mU mL-1 is achieved, which is more sensitive than other spectroscopic methods for ALP detection. Because of its advantages of sensitivity, convenience and versatility, this approach provides a new perspective to disease-related biomolecular detection in the future.

Topics: Alkaline Phosphatase; Ascorbic Acid; Gentian Violet; Gold; Humans; Manganese Compounds; Nanostructures; Oxides; Spectrum Analysis, Raman

In order to detect ascorbic acid (AA) sensitively, a dual-signal optical sensor of a nanosystem with carbon dots (CDs)/MnO

Topics: Ascorbic Acid; Carbon; Fluorescence; Fluorescent Dyes; Limit of Detection; Manganese Compounds; Oxidation-Reduction; Oxides; Quantum Dots; Spectrometry, Fluorescence; Tablets

Exosomes involved in tumor-specific processes display excellent potential in the early diagnosis of cancer. Herein, a highly sensitive plasmonic colorimetric biosensor was proposed for exosome quantification. The sensing strategy mainly includes two steps: exosome-triggered competitive reaction and etching of gold nanobipyramid@MnO

Topics: Alkaline Phosphatase; Ascorbic Acid; Biosensing Techniques; Exosomes; Gold; Humans; Hydrolysis; Manganese Compounds; Nanostructures; Oxides

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

In recent years, α-glucosidase (α-Glu) inhibitor has been widely used in clinic for diabetic and HIV therapy. Although different systems have been constructed for sensitive and selective detection of α-Glu and screening its inhibitor, the method based on ratiometric fluorescence for α-glucosidase inhibitor screening remains poorly investigated. Herein, we constructed a new MnO

Topics: Acarbose; alpha-Glucosidases; Ascorbic Acid; Biomimetic Materials; Enzyme Assays; Fluorescent Dyes; Glycoside Hydrolase Inhibitors; Limit of Detection; Manganese Compounds; Metal Nanoparticles; Oxides; Oxidoreductases; Phenazines; Phenylenediamines; Silver; Spectrometry, Fluorescence

Topics: Ascorbic Acid; Biosensing Techniques; Carbon; Humans; Immunoassay; Insulin; Limit of Detection; Luminescent Agents; Luminescent Measurements; Luminol; Manganese Compounds; Nanospheres; Oxides

In this paper, we report a colorimetric sensor for the rapid, selective detection of ascorbic acid (AA) in aqueous solutions. Single-layered MnO

Topics: Ascorbic Acid; Colorimetry; Food Contamination; Manganese Compounds; Molecular Structure; Nanostructures; Oxides; Solutions; Water

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

This work describes a "switch-on" fluorescence approach for sensing of ascorbic acid (AA) in food samples. In the present method, the fluorescence intensity (FL) of carbon quantum dots (CQDs) was first quenched by addition of MnO2 nanosheets through an inner filter effect to form a CQDs-MnO2 probe. When reductive AA was introduced into the quenched CQDs solution, the added MnO2 was destroyed due to the redox reaction between AA and MnO2 nanosheets, and the FL of the system was recovered. Under the optimal conditions, the limit of detection for AA was 42 nM, with a wide concentration linear range of 0.18-90 μM. Furthermore, the as-fabricated fluorescent sensing system was successfully applied to the analysis of AA in fresh fruits, vegetables, and commercial fruit juices samples with satisfactory results.

Topics: Ascorbic Acid; Fluorescence; Fruit; Limit of Detection; Manganese Compounds; Oxides; Quantum Dots; Spectrometry, Fluorescence; Vegetables

The inhibitory effect of commonly known oxidants and their quenching agents was investigated by employing a battery of toxicity tests. Hydrogen peroxide toxicity could be effectively eliminated by the enzyme catalase, whereas sodium thiosulfate and ascorbic acid were recommended as suitable quenching agents for the removal of the oxidants persulfate and peroxymonosulfate in the Vibrio fischeri bioassays. None of the studied quenching agents was found to be suitable for persulfate and peroxymonosulfate in the Daphnia magna bioassays since high inhibitory effects were obtained for both oxidants. In the case of Pseudokirchneriella subcapitata, manganese dioxide powder should be used as an alternative quenching agent to catalase, since this enzyme exhibited a highly toxic effect towards these microalgae. Sodium sulfite, which is extensively used as a quenching agent, was not appropriate for quenching peroxymonosulfate in all studied bioassays.

Topics: Aliivibrio fischeri; Animals; Antioxidants; Ascorbic Acid; Biological Assay; Catalase; Chlorophyta; Daphnia; Hydrogen Peroxide; Luminescence; Manganese Compounds; Oxidants; Oxidation-Reduction; Oxides; Peroxides; Potassium Compounds; Sulfates; Sulfites; Thiosulfates; Waste Disposal, Fluid; Water Purification

The modification of carbon powder with manganese dioxide using a wet impregnation procedure with electrochemical characterisation of the modified powder is described. The process involves saturation of the carbon powder with manganese(II) nitrate followed by thermal treatment at ca. 773 K leading to formation of manganese(IV) oxide on the surface of the carbon powder. The construction of composite electrodes based on manganese dioxide modified carbon powder and epoxy resin is also described, including optimisation of the percentage of the modified carbon powder. Composite electrodes showed attractive performances for electroanalytical applications, proving to be suitable for the electrochemical detection of hydrogen peroxide, ascorbic acid and nitrite ions with limits of detection comparable to the detection limits achieved by other analytical techniques. The results obtained for detection of these analytes, together with composite electrodes flexible design and low cost offers potential application of composite electrodes in biosensors.

Topics: Ascorbic Acid; Biosensing Techniques; Electrochemistry; Electrodes; Graphite; Hydrogen Peroxide; Manganese Compounds; Nitrites; Oxides; Reproducibility of Results; Sensitivity and Specificity; Temperature

A new and simple flow injection method followed by atomic absorption spectrometry has been developed for the indirect determination of ascorbic acid. The proposed method is based on oxidation of ascorbic acid to dehydroascorbic acid using a solid-phase manganese dioxide (30% m/m suspended on silica gel beads) reactor. The flow of the sample through the column reduces the MnO2 to Mn(II) in an acidic carrier stream of 6.3 mM HNO3 (pH 2.2) with flow rate of 4.0 ml/min at room temperature; Mn(II) is measured by atomic absorption spectrometry. The absorbance of Mn(II) is proportional to the concentration of ascorbic acid in the sample. The calibration curve was linear up to 30 mg/L, with a detection limit of 0.2 mg/L for a 220 microL injected sample volume. The developed procedure was found to be suitable for the determination of AsA in pharmaceuticals and foods with a relative standard deviation better than 1.09% and a sampling rate of about 95 h(-1). The results exhibit no interference from the presence of large amounts of organic compounds. The reliability of the method was established by parallel determination against the 2,6-dichlorophenol-indophenol methods.

Topics: Ascorbic Acid; Beverages; Food Analysis; Fruit; Manganese Compounds; Oxidation-Reduction; Oxides; Reference Standards; Solutions; Spectrophotometry, Atomic; Tablets; Vegetables

We have investigated the activation of p-cresol to form DNA adducts using horseradish peroxidase, rat liver microsomes and MnO(2). In vitro activation of p-cresol with horseradish peroxidase produced six DNA adducts with a relative adduct level of 8.03+/-0.43 x 10(-7). The formation of DNA adducts by oxidation of p-cresol with horseradish peroxidase was inhibited 65 and 95% by the addition of either 250 or 500 microM ascorbic acid to the incubation. Activation of p-cresol with phenobarbital-induced rat liver microsomes with NADPH as the cofactor; resulted in the formation of a single DNA adduct with a relative adduct level of 0.28+/-0.08 x 10(-7). Similar incubations of p-cresol with microsomes and cumene hydroperoxide yielded three DNA adducts with a relative adduct level of 0.35+/-0.03 x 10(-7). p-Cresol was oxidized with MnO(2) to a quinone methide. Reaction of p-cresol (QM) with DNA produced five major adducts and a relative adduct level of 20.38+/-1.16 x 10(-7). DNA adducts 1,2 and 3 formed by activation of p-cresol with either horseradish peroxidase or microsomes, are the same as that produced by p-cresol (QM). This observation suggests that p-cresol is activated to a quinone methide intermediate by these activation systems. Incubation of deoxyguanosine-3'-phosphate with p-cresol (QM) resulted in a adduct pattern similar to that observed with DNA; suggesting that guanine is the principal site for modification. Taken together these results demonstrate that oxidation of p-cresol to the quinone methide intermediate results in the formation of DNA adducts. We propose that the DNA adducts formed by p-cresol may be used as molecular biomarkers of occupational exposure to toluene.

Topics: Animals; Ascorbic Acid; Autoradiography; Biomarkers; Cattle; Chromatography, Affinity; Cresols; DNA; DNA Adducts; DNA Damage; Environmental Exposure; Enzyme Induction; Horseradish Peroxidase; In Vitro Techniques; Indolequinones; Indoles; Manganese Compounds; Microsomes, Liver; Oxidation-Reduction; Oxides; Phenobarbital; Phosphorus Radioisotopes; Quinones

A simple biosensor constructed by bulk-modification of carbon ink with manganese dioxide as a mediator was investigated for its ability to serve as amperometric detector for L-ascorbic acid in hydrodynamic mode. The sensor could be operated at pH 5.0 (0.05 M phosphate buffer) and exhibited excellent reproducibility and stability. Optimization of measurement parameters such as applied working potential and pH value were studied in detail. The screen printed electrode exhibited a linear amperometric increase with the concentration of L-ascorbic acid from 50 mg L(-1) to 250 mg L(-1) and gave a (LOD = 3sigma) detection limit of 0.2 mg L(-1) (1.172 micromol L(-1)). The manganese dioxide modified screen printed electrode shows long term stability.

Topics: Ascorbic Acid; Biosensing Techniques; Calibration; Carbon; Electrochemistry; Electrodes; Manganese Compounds; Oxidation-Reduction; Oxides; Sensitivity and Specificity

This study presents an e.s.r. assay for superoxide dismutase (SOD). Enzymic reactions were studied in which Cu,Zn-SOD, Mn-SOD and Fe-SOD each competed with the spin trap 5,5-dimethyl-1-pyrroline 1-oxide (DMPO) for superoxide anion (O2-) at pH 7.8 O2- from dissolved KO2 (potassium superoxide) in dimethyl sulphoxide was added directly to the enzyme solutions containing DMPO. The results show that, in this competition reaction system, the kinetics of the reactions between the enzymes and O2- follow a function y = f[( SOD]0.5). The rate constant, kSOD = 6.4 x 10(9) M-1. S-1, determined for Cu,Zn-SOD is approximately an order of magnitude larger than those for Mn-SOD and Fe-SOD. A comparative study of reported SOD mimics, including Mn2+, MnO2-desferrioxamine mesylate (Desferal) and MnO2-Desferal-ascorbate, was done. The results show that solutions of these complexes are approximately three orders of magnitude less active than Cu,Zn-SOD and approximately two orders of magnitude less active than Mn-SOD or Fe-SOD. The results also suggest that the reactivity toward O2- in solutions of these complexes originates from the Mn2+ present and not from the MnO2-Desferal complexes.

Topics: Ascorbic Acid; Cyclic N-Oxides; Deferoxamine; Electron Spin Resonance Spectroscopy; Free Radical Scavengers; Hydrogen-Ion Concentration; Iron; Kinetics; Manganese; Manganese Compounds; Oxides; Spin Labels; Superoxide Dismutase; Superoxides

The physicochemical properties of a soluble green complex obtained from the reaction of MnO2 and desferrioxamine have been investigated. The superoxide dismutase mimetic activity of this complex has been previously reported [D. Darr et al. (1987) Arch. Biochem. Biophys. 258, 351-355]. Optical spectra, titration experiments, and metal analyses are consistent with the presence of one gram-atom Mn3+ per mole of desferrioxamine. At least one of the hydroxamate groups is oxidized in the green complex. Reaction of Desferal with MnO2 in the presence of ascorbate yields a more active, pink complex. This pink complex is more stable toward EDTA, suggesting that in it all three hydroxamate groups are intact and ligated to the manganese. The physicochemical properties of these complexes were examined and structures are suggested.

Topics: Ascorbic Acid; Cations; Chelating Agents; Chemical Phenomena; Chemistry; Deferoxamine; Edetic Acid; Manganese; Manganese Compounds; Oxidation-Reduction; Oxides; Spectrophotometry, Infrared; Spectrum Analysis; Superoxide Dismutase

The reactivity between various MnO2+/Mn3+ complexes and ascorbic acid/ascorbate were studied using pulse radiolysis. Experimental results indicate that Mn3+-sulfate reacts with both AH2/AH- via metal-ascorbate complexes. MnO2+-formate and Mn3+-pyrophosphate both appear to react by electron transfer with no evidence of complex formation. All of these metal complexes, with the exception of Mn3+-pyrophosphate, react as fast or faster with ascorbate than free O2-. The significance of this observation in light of metal-induced oxygen toxicity will be discussed.

Topics: Ascorbic Acid; Cations; Formates; Hydrogen-Ion Concentration; Kinetics; Manganese; Manganese Compounds; Oxidation-Reduction; Oxides; Phosphates; Pulse Radiolysis; Solutions; Spectrophotometry; Spectrum Analysis; Sulfates