ABSTRACT
A sensitive and selective colorimetric method based on the incorporation of zinc oxide nanoparticles (ZnO NPs) on the surface of carbon nanotubes (CNTs) was shown to posses synergistic peroxidase like activity for the detection of cholesterol. The proposed nanocomposite catalyzed the oxidation of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) in the presence of hydrogen peroxide (H2O2) to produce a green colored product which can be monitored at 405 nm. H2O2 is the oxidative product of cholesterol in the presence of cholesterol oxidase. Therefore, the oxidation of cholesterol can be quantitatively related to the colorimetric response by combining these two reactions. Under the optimal experimental conditions, the colorimetric response was proportional to the concentration of cholesterol in the range of 0.5-500 nmol/L, with a detection limit of 0.2 nmol/L. The applicability of the proposed assays was demonstrated for the determination of cholesterol in milk powder samples with good recovery results.
Subject(s)
Biomimetic Materials/chemistry , Biosensing Techniques/methods , Cholesterol/analysis , Colorimetry/methods , Nanotubes, Carbon/chemistry , Peroxidases/metabolism , Zinc Oxide/chemistry , Animals , Benzothiazoles/chemistry , Cholesterol Oxidase/chemistry , Cholesterol Oxidase/metabolism , Color , Hydrogen Peroxide/chemistry , Milk/chemistry , Models, Molecular , Nanoparticles/chemistry , Oxidation-Reduction , Protein Conformation , Sulfonic Acids/chemistryABSTRACT
A novel strategy based on direct electrochemistry of amino group on screen printed carbon electrode surface (SPCE) was purposed. The purposed method was employed for the label free detection of ochratoxin A (OTA). A long spacer arm of hexamethyldiamine was immobilized on SPCE via electrochemical oxidation of its terminal amino-group. The activated carboxy-aptamer was covalently linked to other amino terminal group of immobilized hexamethyldiamine. The designed immobilized macromolecules resulted in the formation of long clusters on SPCE surface, while aptamer acted as gate to block the entrance of these clusters. The aptamer gates were closed due to change in conformation of aptamer upon target analyte binding, decreasing the electrochemical signal. The decrease in electrochemical signal was used for the detection of target molecule.
Subject(s)
Carbon/chemistry , Diamines/chemistry , Electrochemical Techniques , Ochratoxins/chemistry , Electrodes , Surface PropertiesABSTRACT
Lymphocyte-dominant pleural inflammation is seen in tuberculous, malignant and immune-mediated pleural disease. We describe two male patients who presented with chest pain and dyspnoea, in whom radiological and histological investigations showed idiopathic lymphocytic pleuritis that responded to immunosuppressive therapy with corticosteroids and/or azathioprine. Corticosteroid-responsive pleuritis has been described in association with many conditions, but little is known of idiopathic lymphocytic pleuritis. The authors suggest that patients with idiopathic pleural thickening undergo early thoracoscopic pleural biopsy, and that immunosuppressant therapy be considered for patients with idiopathic lymphocytic pleuritis.
