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Peteu S.F.,Cleveland State University | Peteu S.F.,National Institute for R and D in Chemistry and Petrochemistry ICECHIM | Bose T.,Cleveland State University | Bayachou M.,Cleveland State University | Bayachou M.,Cleveland Clinic
Analytica Chimica Acta | Year: 2013

Peroxynitrite (ONOO-) constitutes a major cytotoxic agent, implicated in a host of pathophysiological conditions, thereby stimulating a tremendous interest in evaluating its role as an oxidant in vivo. Some of the detection methods for peroxynitrite include oxidation of fluorescent probes, EPR spectroscopy, chemiluminescence, immunohistochemistry, and probe nitration; however, these are more difficult to apply for real-time quantification due to their inherent complexity. The electrochemical detection of peroxynitrite is a simpler and more convenient technique, but the best of our knowledge there are only few papers to date studying its electrochemical signature, or reporting amperometric microsensors for peroxynitrite. Recently, we have reported the use of layered composite films of poly(3,4-ethylenedioxythiophene) (PEDOT) and hemin (iron protoporphyrin IX) as a platform for amperometric measurement of peroxynitrite. The main goal herein is to investigate the intrinsic catalytic role of hemin electropolymerized thin films on carbon electrodes in oxidative detection of peroxynitrite. The electrocatalytic oxidation of peroxynitrite is characterized by cyclic voltammetry. The catalytic current increased as a function of peroxynitrite's concentration, with a peak potential shifting positively with peroxynitrite's concentration. The catalytic efficiency decreased as the scan rate increased, and the peak potential of the catalytic oxidation was found to depend on pH. We show that optimized hemin-functionalized carbon electrodes can be used as simple platforms for peroxinitrite detection and quantification. We report dose-response amperometry as an electroanalytical determination of this analyte on hemin films and we contrast the intrinsic hemin catalytic role with its performance in the case of the PEDOT-hemin as a composite matrix. Finally, we include some work extending the use of simple hemin films for peroxynitrite determination on carbon microfiber electrodes in a flow system. © 2013 Elsevier B.V. Source


Panaitescu D.M.,National Institute for R and D in Chemistry and Petrochemistry ICECHIM | Frone A.N.,National Institute for R and D in Chemistry and Petrochemistry ICECHIM | Ghiurea M.,National Institute for R and D in Chemistry and Petrochemistry ICECHIM | Chiulan I.,National Institute for R and D in Chemistry and Petrochemistry ICECHIM
Industrial Crops and Products | Year: 2015

Cellulose nanofibers (CN) with high aspect ratio were obtained and their transverse modulus (Et) was determined for the first time by peak force (PF) QNM (quantitative nanomechanical mapping). The PF QNM value of Et (18.8. GPa) was comparable with that of cellulose determined by other methods. CN were used as reinforcements in starch/poly(vinyl alcohol) (S/PVA) cross-linked films and the influence of storage conditions on the properties of these films was investigated in this paper. It was found that over 4. wt%, CN form a real network and hinder starch recrystallization. CN determined a significant increase of strength and stiffness of S/PVA depending on storage conditions. Two fold increase of modulus was observed in thermal treated samples compared to fresh ones and the increase of both strength and modulus in samples exposed to humid atmosphere. PF QNM successfully explains the influence of moisture on the properties of the films exposed to humid atmosphere, emphasizing new well organized sub-micron amorphous formations on their surface. Starch films with 7. wt% CN showed strength and stiffness close to that of polyolefines (19.5. MPa and 1199. MPa, respectively), and can be seen as a low cost "green" substitute for application in food packaging and conservation. © 2015 Elsevier B.V. Source

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