ascorbic-acid and 4-phenylenediamine

Ascorbic acid (AA) is an important diet-derived antioxidant to human body. Thus, efficient and accurate detection of AA is of considerable significance in food analysis. Herein, smartphone assisted colorimetric and fluorescent triple-channel signal sensor has been developed for AA monitoring based on oxidase-like CoOOH nanoflakes. CoOOH nanoflakes can efficiently catalyze the oxidation of p-phenylenediamine (p-PD) into reddish brown p-PDox. The carbon dots (C-dots) are further introduced, of which the fluorescence can be quenched by p-PDox. However, in the presence of AA, the CoOOH nanoflakes is reduced and thus collapsed. As a result, the oxidation of p-PD is restrained, and thus the fluorescence of C-dots keeps strong. Based on AA induced light color, low absorbance, and strong fluorescence, triple-channel signal sensor has been proposed for AA determination. The AA assay shows a dynamic response range from 0.5 to 10 μM with a detection limit of 0.09 μM. The method assay allows detection of AA in real samples such as fruit juices. Combination with portable smartphone, the developed sensor is potential for AA determination in resource-poor settings.

Topics: Ascorbic Acid; Cobalt; Colorimetry; Food Analysis; Fruit and Vegetable Juices; Nanostructures; Oxidation-Reduction; Oxides; Oxidoreductases; Phenylenediamines; Smartphone

In this work, a label-free electrochemical immunosensor was constructed on the base of poly p-phenylenediamine (PPD) and GR nanocomposite (PPD-GR). Screen-printed electrodes modified with PPD-GR nanocomposite and applied to advance enzyme-free and label free electrochemical immunosensor for detection of protein biomarker neuron-specific enolase (NSE). It was found that the PPD-GR nanocomposite exhibits excellent electrocatalytic activity towards ascorbic acid (AA) oxidation as analytical signal based on EC' mechanism. Due to the excellent electrocatalytic activity of PPD-GR nanocomposite, determination of NSE antigen was based on its obstruction to the electrocatalytic oxidation of AA after binding to the surface of electrode through interaction with the anti-NSE. The proposed immunosensor exhibited a wide linear range of 1.0-1000 ng mL

Topics: Ascorbic Acid; Electrochemical Techniques; Graphite; Humans; Immunoassay; Nanocomposites; Oxidation-Reduction; Phenylenediamines; Phosphopyruvate Hydratase

An allergic contact reaction is accompanied by high oxidative stress in the skin. Pretreatment of the skin with antioxidative substances could reduce the elicitation reaction.. To investigate, in a proof-of-principle study, whether pretreatment of the skin with the antioxidant ascorbic acid reduces the elicitation reaction to a p-phenylenediamine (PPD)-containing hair dye in sensitized subjects.. Twelve subjects with contact allergy to PPD, a documented skin reaction to a hair dye simulation exposure model and a history of hair dye-related skin complaints were included in this study. Skin areas on the forearms were, in a left versus right design, exposed to an emulsion with ascorbic acid and an emulsion without ascorbic acid, and then to a 2% PPD-containing hair dye testing formulation. In addition, control areas were exposed to the emulsions and to the PPD-containing hair dye formulation without pretreatment. Skin reactions were graded on day (D)2 and D3.. Pretreatment with ascorbic acid emulsion resulted in a reduction in the elicitation reaction in 7 of 12 subjects at D3 (p = 0.046). No statistically significant difference was observed at D2.. Pretreatment of the skin with the antioxidant ascorbic acid had an attenuating effect on the elicitation reaction to PPD in sensitized individuals.

Topics: Adolescent; Adult; Aged; Antioxidants; Ascorbic Acid; Coloring Agents; Dermatitis, Allergic Contact; Female; Humans; Male; Middle Aged; Oxidative Stress; Patch Tests; Phenylenediamines; Premedication; Skin; Young Adult

Hair dyes represent one of the most important causes of allergic contact dermatitis resulting from the use of cosmetic products. The principal causative chemistry is associated with oxidation products of p-phenylenediamine (PPD) and closely related substances.. To examine whether prior application of the antioxidant vitamin C to the skin was able to reduce the cutaneous allergic response to PPD.. Twenty eight volunteers with a proven history of contact allergy to PPD were recruited. Each was tested with a range of PPD doses and PPD-containing hair dye on untreated skin and skin pretreated for 10 min with a vitamin C formulation.. Pretreatment of skin sites with vitamin C led to a reduction in the intensity, or even ablation, of the cutaneous allergic reaction to PPD in ∼75% of cases as compared with untreated skin.. The results suggest that treatment of the skin adjacent to the hair-bearing area with antioxidant could form part of a strategy to reduce the burden of cosmetic allergic contact dermatitis caused by hair dyeing.

Topics: Antioxidants; Ascorbic Acid; Coloring Agents; Dermatitis, Allergic Contact; Hair Dyes; Humans; Patch Tests; Phenylenediamines; Premedication; Severity of Illness Index

Topics: Ascorbic Acid; Biphenyl Compounds; Coloring Agents; Hemoglobins; Humans; Iron; Phenylenediamines; Vitamin E; Vitamins