Determination of Quercetin by a Siloxane-Polyester/Poly-L-Lysine Nanocomposite Modified Glassy Carbon Electrode

Abstract

The aim of this study was to evaluate the oxidant profile and iron metabolism in serum of dogs infected by Ehrlichia canis. Banked sera samples of dogs were divided into two groups: negative control (n ¼ 17) and infected by E. canis on acute (n ¼ 24), and subclinical (n ¼ 18) phases of the disease. The eritrogram, leucogram, and platelet counts were evaluate as well as iron, ferritin, and transferrin levels, latent iron binding capacity (LIBC), and transferrin saturation index (TSI) concentration. In addition, the advanced oxidation protein products (AOPP) and ferric reducing ability of plasma (FRAP) in sera were also analyzed. Blood samples were examined for the presence of E. canis by PCR techniques. History and clinical signals were recorded for each dog. During the acute phase of the disease, infected animals showed thrombocytopenia and anemia when compared to healthy animals (P < 0.05) as a consequence of lower iron levels. Ferritin and transferrin levels were higher in both phases (acute and subclinical) of the disease. The AOPP and FRAP levels increased in infected animals on the acute phase; however, the opposite occurred in the subclinical phase. We concluded that dogs naturally infected by E. canis showed changes in the iron metabolism and developed an oxidant status in consequence of disease pathophysiology.

Signal-Enhanced Electrochemical Determination of Quercetin with Poly(chromotrope fb)-Modified Pencil Graphite Electrode in Vegetables and Fruits

“…The ratio of proton to electron was calculated as 1 from the E p –pH curve having a slope of −68.6 mV/pH (Figure S9). This coincides with the oxidation of Qn including the 2-electron and 2-proton process reported in the literature (Figure A). , …”

“…This coincides with the oxidation of Qn including the 2-electron and 2-proton process reported in the literature ( Figure 1 A). 9 , 23 …”

“…This coincides with the oxidation of Qn including the 2electron and 2-proton process reported in the literature (Figure 1A). 9,23 In addition, cyclic voltammograms were recorded with bare PGE, aPGE, and pCFB/aPGE in solution containing Qn to indicate the electrocatalytic effect as shown in Figure 4. The peak currents of Qn oxidation were found as 9.77, 19.92, and 43.02 μA for bare PGE, aPGE, and pCFB/aPGE, respectively.…”

“…Although these methods yield in terms of sensitivity and selectivity, they employ labor-intensive pretreatment steps, difficult separation procedures, and sophisticated and expensive instruments. , In recent years, electrochemical sensors have come to the forefront for determining some electroactive food and biologically essential substances. − Due to some distinct features of electrochemical methods such as being simple, quick, portable, cost-effective, sensitive, and selective, they have become one of the most encouraging methods for determining Qn. , A wide variety of modified electrodes including single- or multipolymer film-modified electrodes with or without metal nanoparticles, − carbon nanotube-based electrodes with or without polymer films, , molecularly imprinted polymer (MIP)-based electrodes, , and the other ones , have been reported for the determination of Qn, and they are summarized in Table S1. The electrodes composed of a single polymer , have high limit of detection (LOD) values (i.e., 0.17 and 20 μM); the other electrodes have complex and time-consuming preparation steps, ,,− and the supporting surfaces in these studies, i.e., glassy carbon electrodes (GCEs), carbon paste electrodes (CPEs), and paraffin-impregnated graphite disk electrode, have advantages such as being prone to electrocatalysis, resistant to surface contamination, and undesired electrode reactions. − However, they have disadvantages due to being expensive, nondisposable, and requiring pretreatment. On the other hand, pencil graphite electrodes (PGEs) have some benefits involving cheapness, common technology, good electrochemical reactivity and mechanical endurance, and being disposable, commercially available, renewable, and suitable for modification. ,,, It has been reported that the polymer formed as a result of the uniform arrangement of azo dyes containing a hydroxyl group in the ortho position to the azoic group forms a stable redox-active layer, increases the electrode active surface area, and has an electrocatalytic effect toward the oxidation of small organic molecules with adjacent hydroxyl grou...…”

“… 19 , 20 A wide variety of modified electrodes including single- or multipolymer film-modified electrodes with or without metal nanoparticles, 21 − 25 carbon nanotube-based electrodes with 26 or without polymer films, 27 , 28 molecularly imprinted polymer (MIP)-based electrodes, 29 , 30 and the other ones 31 , 32 have been reported for the determination of Qn, and they are summarized in Table S1 . The electrodes composed of a single polymer 21 , 24 have high limit of detection (LOD) values (i.e., 0.17 21 and 20 μM 24 ); the other electrodes have complex and time-consuming preparation steps, 22 , 23 , 25 − 32 and the supporting surfaces in these studies, i.e., glassy carbon electrodes (GCEs), carbon paste electrodes (CPEs), and paraffin-impregnated graphite disk electrode, have advantages such as being prone to electrocatalysis, resistant to surface contamination, and undesired electrode reactions. 33 − 38 However, they have disadvantages due to being expensive, nondisposable, and requiring pretreatment.…”