Oxidation Of Epinephrine Research Articles

Влияние пирролидиновых производных 2,6-ди-трет-бутилфенола на супероксид- и пероксид водорода-утилизирующую активность спермы сибирского осетра

The effect of (3.5-di-tert-butyl-4-hydroxyphenyl)-pyrrolidine-2-carboxylic acid derivatives on the ability of Siberian sturgeon (Acipenser baerii, Brandt, 1869) sperm to utilize superoxide anion radical (O2–•) generated in a model system of adrenaline oxidation in an alkaline medium, as well as exogenous hydrogen peroxide (H2O2) before and after freezing at liquid nitrogen temperature for 3 days was studied. The study of this activity of phenolic derivatives was carried out in comparison with the reference antioxidant Trolox, a water-soluble analogue of vitamin E. When phenolic derivatives were added at a concentration of 0.1 mM to the basic Stein cryomedium containing 12.5% egg yolk, 12.5% DMSO, 5 mM KCl, 130 mM NaCl, 20 mM NaHCO3 and 5.5 mM glucose, a multidirectional effect of the compounds on the ability of Siberian sturgeon sperm to utilize superoxide anion radical and hydrogen peroxide before and after the freezing-defrosting process was established. The studied compounds increase the H2O2-utilizing activity of reproductive cells, while reducing their superoxide-utilizing activity. Pyrrolidine derivatives of phenol were found to be more effective in stimulating the H2O2-utilizing activity of defrosted sperm of the Siberian sturgeon than Trolox. A decrease in the rate of O2– • and H2O2 utilization by fish sperm was found after cryopreservation in the control and in the presence of (3.5-di-tert-butyl-4-hydroxyphenyl)-pyrrolidine-2-carboxylic acid derivatives. A protective effect of new phenolic derivatives on the enzymatic link of antioxidant protection of Siberian sturgeon sperm during cryopreservation was shown. The obtained results indicate the prospects for further studies of the protective activity of (3.5-di-tert-butyl-4-hydroxyphenyl)-pyrrolidine-2-carboxylic acid derivatives in the process of cryopreservation of reproductive cells of rare, endangered and commercially valuable fish species.

Non-pyrolytic synthesis of laccase-like iron based single-atom nanozymes for highly efficient dual-mode colorimetric and fluorescence detection of epinephrine

Single-atom nanozymes have garnered significant attention due to their exceptional atom utilization and ability to establish well-defined structure-activity relationships. However, conventional pyrolytic synthesis methods pose challenges such as high energy consumption and random local environments at the active sites, while achieving non-pyrolytic synthesis of single-atom nanozymes remains a formidable technical hurdle. The present study focuses on the synthesis of laccase-like iron-based single-atom nanozymes (Fe-SAzymes) using a non-pyrolysis method facilitated by microwave irradiation. Under low iron loading conditions, Fe-SAzymes exhibited significantly enhanced laccase activity (12.1 U/mg), surpassing that of laccase by 24-fold. Moreover, Fe-SAzymes demonstrated efficient catalytic oxidation of epinephrine (EP), enabling its colorimetric detection. Owing to the remarkable laccase activity of Fe-SAzymes, the conventional nanozymes EP detection time was reduced from 60 min to 20 min, with an impressive low detection limit as low as 2.95 μM. In addition, an ultra-sensitive fluorescence method for EP detection was developed using the internal filter effect of EP oxidation products and CDs combined with carbon dots probe. The detection limit of fluorescence method was only 0.39 μM. Therefore, an visual, fast, and highly sensitive dual-mode EP detection strategy has great potential in the clinical diagnostic industry.

A novel copper ion enhanced electrochemical DNA biosensor for the determination of epinephrine

A novel electrochemical biosensor was developed for the detection of epinephrine (EP) by immobilizing double-strand DNA (dsDNA) bound with copper ions on a gold electrode (Cu2+/dsDNA/MCH/AuE). The electrochemical behavior of EP at Cu2+/dsDNA/MCH/AuE was examined, and the results demonstrated a significant enhancement in the electrocatalytic oxidation peak current of EP due to the formation of a stable G-Cu(II)-G sandwich structure between Cu2+ and guanine at the modified electrode. The modification process of the electrode was characterized by scanning electron microscopy, infrared spectroscopy, electrochemical impedance spectroscopy, and differential pulse voltammetry. A study on the effect of pH in phosphate buffer solution on the electrochemical oxidation of EP indicated that the catalytic oxidation process was pH-dependent. A plot of catalytic current versus EP concentration exhibited a dual-linear relationship within two ranges: 1.0–12.5 μM and 12.5–1000.0 μM, with correlation coefficients of 0.995 and 0.997, respectively. The limit of detection was determined to be 47 nM (S/N = 3). According to the calculated Hill coefficient (0.99), it can be concluded that the electrocatalytic process followed the Michaelis-Menten kinetic mechanism. The maximum catalytic current Im was 25 μA, while the apparent Michaelis-Menten constant Km was 1.425 mM. These findings indicated excellent electrocatalytic activity of the modified electrode towards oxidation of EP. The developed biosensor successfully detected EP in spiked mouse serum as well as epinephrine hydrochloride injection with high selectivity, sensitivity, stability, and accuracy.

Development of PEG-coated iron oxide nanoparticles for the oxidation of adrenaline

Development of PEG-coated iron oxide nanoparticles for the oxidation of adrenaline

Patterned Au@Ag nanoarrays with electrically stimulated laccase-mimicking activity for dual-mode detection of epinephrine

Epinephrine (EP) is a crucial neurotransmitter in the central nervous system. However, an abnormal level of EP in biological fluids can lead to various diseases. Therefore, it is essential to rapidly and accurately detect EP content. Herein, electrically stimulated patterned Au@Ag nanoarrays with laccase-mimicking activity were designed for the dual-mode detection of EP concentration. The patterned Au@Ag nanoarrays exhibit excellent electrochemical properties and electrically stimulated laccase-mimicking activity. They provide sensitive electrochemical responses for detecting EP content. Simultaneously, the Au@Ag nanoarrays can catalyze the oxidation of EP, enabling its detection through a colorimetric process. This dual-mode approach achieves the detection of EP content over a wide linear range of 0.5–200 μM, with a low detection limit of 0.152 μM. Furthermore, the utility of these nanoarrays for sensing EP in human serum was evaluated. This work provides a convenient method using patterned nanozyme array for the visible, rapid and accurate detection of EP content. It provides the important implication for the development of portable and reliable on-site analytical instruments.

Ultrasound and defect engineering-enhanced nanozyme with high laccase-like activity for oxidation and detection of phenolic compounds and adrenaline

Perusing metal-based redox nanozyme offers new opportunity for pollutant removal and biosensor, but ultrasound (US)-driven laccase-like nanozyme remains a significant challenge, especially in combination with defect engineering strategy. Herein, the Cu2Ov@Ce-TCPP was synthesized by doping Ce3+ on the surface of Cu2O nanocube and then coating with the porphyrin sonosensitizer. The Ce-doped porphyrin metal-structure in nanozyme was demonstrated to generate oxygen vacancy defects, which could obviously promote the laccase-like activity of Cu2Ov@Ce-TCPP nanozyme under US. XPS characterization and density functional theory (DFT) theoretical calculation revealed that the ultrasonic stimulation is beneficial to accelerate the electron transfer rate and O2 adsorption to improve catalytic activity, and Cu2Ov@Ce-TCPP nanozyme exhibits low adsorption energy and activation energy due to the presence of oxygen defect site, resulting in high laccase-like activity. The interaction between Ce atom and porphyrin structure also improved the sonocatalytic ability of the nanozyme. Meanwhile, Cu2Ov@Ce-TCPP nanozyme has been used for detecting and degrading a series of phenolic compounds. The detection adrenaline method has a linear range of 3.3–1000 μM and a detection limit as low as 0.96 μM with good reproducibility. The developed US-enhancing and recyclable laccase-like nanozyme system provides a promising strategy for the oxidation and detection of phenolic compounds.

Zeolite Imidazolate Framework-Based Platform for the Electrochemical Detection of Epinephrine

In this study, we employed a zeolite imidazolate framework (ZIF-67) modified glassy carbon electrode (GCE) as a platform for the electrochemical detection of epinephrine. The ZIF-67 modified glassy carbon electrode (GCE) exhibited excellent electrocatalytic activity towards the detection of epinephrine in phosphate buffer (PBS, pH 7.0). The proposed ZIF-67 displayed superior electrocatalytic activity towards the oxidation of epinephrine in the 0.5−50 μM linear range with a limit of detection (LOD) of 2.1 μM, and a sensitivity of 0.06 μA μM−1 cm−2. The efficacy of the proposed biosensor was demonstrated for the direct determination of epinephrine from serum and urine samples. All these results confirmed the usefulness of ZIF-67 modified electrodes for clinical analysis.

Bioinspired CuZn-N/C Single-Atom Nanozyme with High Substrate Specificity for Selective Online Monitoring of Epinephrine in Living Brain.

Though many elegant laccase mimics have emerged, these mimics generally have no substrate selectivity as well as low activity, making it difficult to fulfill the demand for monitoring in physiological conditions. Herein, inspired by the Cu-N ligand structure in the active site of natural laccase, we revealed that a carbon nanomaterial with atomically dispersed Cu and Zn atoms (CuZn-N/C) and a well-defined ligand structure could function as an effective laccase mimic for selectively catalyzing epinephrine (EP) oxidation. Catalytic activity of the CuZn-N/C nanozyme was superior to those of Cu-N/C and Zn-N/C and featured a Km value nearly 3-fold lower than that of natural laccase, which indicated that CuZn-N/C has a better affinity for EP. Density functional theory (DFT) revealed the mechanism of the superior catalytic ability of dual-metal CuZn-N/C as follows: (1) the exact distance of the two metal atoms in the CuZn-N/C catalyst makes it suitable for adsorption of the EP molecule, and the CuZn-N/C catalyst can offer the second hydrogen bond that stabilizes the adsorption; (2) molecular orbitals and density of states indicate that the strong interaction between the EP molecule and CuZn-N/C is important for EP catalytic oxidization. Furthermore, a sensitive and selective online optical detection platform (OODP) is constructed for determining EP with a low limit of detection (LOD) of 0.235 μM and a linear range of 0.2-20 μM. The system allows real-time measurement of EP release in the rat brain in vivo following ischemia with dexmedetomidine administration. This work not only provides an idea of designing efficient laccase mimics but also builds a promising chemical platform for better understanding EP-related drug action for ischemic cerebrovascular illnesses and opens up possibilities to explore brain function.

Kinetics and Mechanism of Epinephrine Autoxidation in the Presence of Plant Superoxide Inhibitors: A New Look at the Methodology of Using a Model System in Biological and Chemical Research.

Superoxide is the primary active oxygen form produced in living organisms. Because of superoxide anion radical formation during epinephrine oxidation in alkaline medium, this system is offered in some works for antioxidant activity analysis, however, without enough physicochemical justification. Therefore, the task of developing reliable methods for analyzing the superoxide inhibition activity of various objects is very urgent. In this work, a kinetic model of epinephrine autoxidation in an alkaline medium in the presence of antioxidants of plant origin is proposed. The participation of chain reactions with long oxidation chains in this process is revealed. The limiting stage of the process is a one-electron reduction of oxygen by the anionic forms of the phenolic hydroxyls of epinephrine. The appearance of the absorption maximum at a wavelength of 347 nm during epinephrine autoxidation is associated with adrenolutin formation, which is confirmed by HPLC/UV/MS. No adduct formation between phenolic antioxidants and epinephrine oxidation products was found. The complex U-shaped character of epinephrine autoxidation rate dependence on the content of antioxidants in the reaction system was shown. The study of the kinetics of epinephrine autoxidation in the presence of an individual phenolic plant superoxide inhibitor, chlorogenic acid, was carried out for the first time. The inhibitory effect of yarrow, chamomile, and bur beggar-ticks plant extracts in the adrenaline system was examined.

Superoxide dismutase activity levels in parturients on intermittent preventive treatment with sulphadoxine pyrimethamine and their controls at current confinements

Malaria prevention in pregnancy especially in endemic areas has been greatly emphasized. This is especially so during the antenatal periods. Malaria prevention is important for reducing the problems of malaria in pregnancy. Early trimester miscarriages, preterm labours, anaemia in pregnancy, small for date babies and increased admissions into special care baby units are some of the problems encountered that are traceable to malaria infection. It is also noteworthy that some favourable antioxidants have been noted to help pregnant women enjoy and cope with their pregnancies. In that same way, it has also been noted that optimal levels of superoxide dismutase is equally necessary to help pregnant women enjoy uneventful pregnancies as well as stay free from some problems associated with malaria in pregnancy. Objectives: We have comparatively and objectively assessed the plasma Levels of superoxide dismutase in Parturients on Intermittent Preventive Treatment with Sulphadoxine Pyrimethamine and their Controls at Current Confinements. Method: This comparative study was conducted at the Obstetrics and Gynaecology Department of the Federal Medical Centre (FMC) Owerri, South East Nigeria. Owerri is widely known for its heavy malaria endemicity. Prior to participant recruitment, appropriate ethical clearance was applied for and obtained from the ethics committee of FMC Owerri. This enabled the commencement of the longitudinal recruitment of participants after due counseling and adequate informed consent involving both study groups. This bench-based research and cross-sectional descriptive study involved two hundred and ninety-six (296) consented participants. The participants were made to understand clearly the study protocol as well as satisfy the inclusion criteria for either the study (case) or control groups. Upon recruitment, participants were then followed up all throughout their entire antenatal course culminating in the delivery. The follow up enabled the collection of blood samples for the estimation of Superoxide Dimutase (SOD) plasma levels at delivery. The SOD levels were estimated using the Misra and Fridovich method, 1972. The ability of superoxide dismutase to inhibit the auto oxidation of adrenaline at pH 10.2 makes this reaction a basis for the SOD assay. Superoxide anion (O2) generated by the xanthine oxidase reaction is known to cause the oxidation of adrenaline to adrenochrome. The yield of adrenochrome produced per superoxide anion introduced increased with increasing pH and also with increasing concentration of adrenaline. These led to the proposal that auto oxidation of adrenaline proceeds by at least two distinct pathways, one of which is a free radical chain reaction involving superoxide radical and hence could be inhibited by SOD. Data analysis: Data computation and analysis were done using the computer Software Package for Social Science (SPSS) version 20.0 (SPSS, Inc, 2007, Chicago). Important descriptive statistics (mean, standard deviation, range, percentages etc) were determined for continuous variables. P-value less than (<0.05) at 95% confidence interval was considered statistically significant. Result: The mean serum level of superoxide dismutase (SOD) in the study group was 12.61 U/ml ± 3.105 while the minimum and maximum serum superoxide dismutase were 7 and 20 U/ml respectively. For their controls, the mean serum level of superoxide dismutase was 11.69 U/ml ± 2. 969. However, the minimum and maximum serum superoxide dismutase were 7 and 20 U/ml respectively. The difference was found to be statistically significant (p= 0.011) with odds ratio 1.12 (CI of 95% 1.024-1.193).

A novel, extreme low-cost poly (Erythrosine) modified pencil graphite electrode for determination of Adrenaline

A simple, novel, and less cost yellow (Erythrosine) modified pencil graphite electrode (Po-ERY/MGPE) was successfully fabricated via electropolymerization method using cyclic voltammetric techniques. The fabricated Po-ERY/MGPE opted as a sensor for the detection of Adrenaline (ADR) in 0.2 M PBS (7.4 pH). This reported senor displayed excellent electrocatalytic activity, increased sensitivity, high stability, superior electron transfer kinetics in the oxidation of ADR once relative to BGPE. The significance of pH, scan rate, and impact of concentration was assessed at the sensor. As per the pH and scan rate study, redox routes carry the same number of electrons and protons, and electro-oxidation of ADR was adsorption controlled respectively. The LOD of ADR was found to be 0.499 µM. The DPV data indicate that there is a significant peak divergence among ADR and uric acid (UA) which could make it easier to determine them alone and simultaneously on the sensor. The described method has been employed for the determination of ADR in injection sample. Good recovery values indicate the efficacy and applicability of the sensor in detecting ADR.

SYNTHESIS AND PRECLINICAL STUDY OF ANTIOXIDANT ACTIVITY OF [1,2,4]TRIAZOLO[1,5-A]PYRIDINE DERIVATIVES

Purpose. Synthesis and study of antioxidant properties of [1,2,4]triazolo[1,5-a]pyridine derivatives and their potential toxicity using preclinical diagnostic methods. Methodology. Derivatives of [1,2,4]triazolo[1,5-a]pyridine were synthesized on the basis of 2-aminopyridines and ethyl isothiacyanatocarbonate, with subsequent cyclization of intermediate adducts. The resulting 2-amino[1,2,4]triazolo[1,5-a]pyridines were reacted with isoamyl nitrite in the presence of CuHal2, which led to the synthesis of volatile 2-halogeno[1,2,4]triazolo[1,5- a]pyridine. The toxicity of the obtained compounds was studied by the degree of hemolysis of erythrocytes in a hypotonic NaCl solution. The intensity of free-radical oxidation of lipids was assessed spectrophotometrically by the formation of TBА-active products. The antioxidant activity of the substances was determined by inhibiting the oxidation of adrenaline under conditions of artificial oxidative stress. Scientific novelty. For the first time, the antioxidant activity of the [1,2,4]triazolo[1,5-a]pyridine derivatives described in the paper was investigated and their toxicity was studied according to the degree of hemolysis of erythrocytes in a hypotonic NaCl solution. Conclusions. The in vitro cytotoxicity study model showed that compounds 5a and 5b, which contain bromine atoms in the 2, 5, and 7 positions of the pyridinotriazole heterosystem, exert the greatest influence on the stability of erythrocyte membranes. The study of antioxidant activity showed that the highest values of antioxidant activity are characteristic of compounds of the 4a-d series, namely compounds 4b and 4c, which are characterized by the presence of an amino group in the 2nd position and the presence of a bromine atom as a substitute in the 1st and 5th positions of the pyridine fragment of the heterosystem. The dynamics of antioxidant activity on the model of inhibition of adrenaline oxidation confirms the opinion about the lowest toxicity and the highest ability to inhibit the formation of reactive oxygen species of compounds 4b and 4c (40.16 and 38.82% relative to ionol). So, with the use of preclinical diagnostic methods, we proved the presence of physicochemical activity in a number of investigated compounds. 2-amino-[1,2,4]triazolo[1,5a]pyridine derivatives with a bromine atom as a substitute in the pyridine fragment of the molecule should be considered as potential antioxidants in the future, and the studied condensed system can be considered a promising heterocyclic framework for creating potential antioxidant agents.

A Layered Electrochemical Sensor for Epinephrine Based on a Nitrogen‐Doped Reduced Graphene Oxide‐ZnFe2O4/β‐Cyclodextrin‐Modified Platinum Electrode

AbstractA novel nanocomposite of nitrogen‐doped reduced graphene oxide‐ZnFe2O4/β‐cyclodextrin (NRGO‐ZnFe2O4/β‐CD) was synthesised for electrocatalytic applications on platinum electrode. The structural and morphological characterisation of the synthesised nanocomposite was carried out using FTIR, XRD, EDAX, FESEM, HRTEM etc. The electrochemical characterisation was performed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). NRGO‐ZnFe2O4/β‐CD proved to be an excellent electrocatalyst for the electrochemical detection of epinephrine on platinum electrode and the optimum pH for the response was found to be 7. The electrochemical characteristics of the oxidation of epinephrine was found to be quasi reversible and diffusion controlled with charge transfer coefficient and diffusion coefficient of 0.55 and 1.03×10−5 cm2/s respectively. Detection limit in the micromolar range of epinephrine was achieved with specific recognition in presence of other structurally similar catecholamines like norepinephrine and dopamine even in their ten‐fold excess concentration at β‐CD/NRGO‐ZnFe2O4/Pt electrode and the electrode exhibited good repeatability, excellent reproducibility and stability for the oxidation of epinephrine. Recognition of epinephrine with high selectivity could be attained in presence of other common substances present in biological fluids.

Thermostable Superoxide-Producing Complex Between NADPH-Containing Lipoprotein (NCL) And Fe (III) From Boiled Cow Milk: Activation Of Immune Cells NADPH Oxidase By NCL In Vitro

О2−-producing complexes or associates have recently been isolated from blood serum, goat milk, erythrocyte, leukocyte membranes, and medicinal plant membranes. Fe(III) ions in these complexes act as bridges for electron transfer from NADPH-containing lipoprotein (NCL) to molecular oxygen, reducing it up to О2−. On the other hand, NADPH oxidase (Nox) of erythrocytes and leukocytosis are activated by NCL in vitro. In fact, both serum and milk contain NCL. The main systems for the production of О2− in mammalian milk and blood, as previously stated, are polymorphonuclear leukocytes, as well as О2−-producing complex between NCL and Fe (III). At the same time, Fe(III) ions can be found in milk, and anemia can result from a Fe(III) deficiency in milk. The superoxide (О2−) - producing thermostable complex between NCL and Fe(III): NCL-Fe(III) was isolated and purified from raw and boiled cow milk, for the first time. The specific О2−-producing activity of NCL-Fe(III) complex from milk, before and after boiling, practically does not change as a result of milk boiling (this activity decreases by only 7-8%). After incubating an aqueous mixture of NCL (5 mg/ml) with an aqueous solution of Nox1 + Nox2 (erythrocytes or leukocytes membranes) isoforms, 5 mg/ml, at 37°C for 40 minutes, an ion exchange chromatography was performed on the column of DE cellulose, equilibrated by water at pH9.5. The hNCL-Nox associate eluates from this column with water at pH9.5 The specific О2−-producing activity of hNCL-Nox isoforms of EM and LM basically does not decrease when compared to the NCL-Fe(III) complex. This is a promising finding, suggesting that milk NCL has stimulating the Nox from erythrocytes or leukocyte membranes in vitro does not decrease even after boiling. In contrast to these О2−-producing associates or complexes, NCL isolated from them, suppresses the oxidation of adrenaline to adrenochrome, exerting a reducing-antioxidant effect due to NADPH electrons in its composition (the Cu, Zn-SOD does not inhibit this process). The NCL isolated from this complex, at the expense of NADPH, has a reductive (antioxidant) influence and forms a hybrid О2−-producing associate with isoforms of the NADPH oxidase from erythrocytes and leukocytes membranes. Thus the properties of the thermostable complex NCL-Fe(III): О2−-producing activity, as well as the reductive (antioxidant) activity of NCL, are practically preserved after milk boiling during 10-12 min.

STUDY OF ADRENALIN AUTOOXIDATION WITH UV-VIS SPECTROSCOPY METHODS

The process of adrenaline autoxidation in an alkaline medium (pH=10.65) in the presence of sulfite was experimentally studied by UV-Vis spectroscopy. The absorption spectra of the final product of autoxidation (λm = 290—300 nm, εm = 8400 М–1 · cm–1 ), the intermediate adduct of adrenochrome with sulfite (λm = 343 nm, εm= 68000 М–1 · cm–1), and the reactive an intermediate product, presumably adrenolutin (λm = 311, εm = 140000 М–1 · cm–1 and λm = 373 nm, εm = 129000 М–1 · cm–1) were determined with experimental data processing. The estimated equilibrium constant for the formation of adrenochrome adduct with sulfite 5000 M-1
 agrees with the literature data for carbonyl compounds. The results obtained explain the contradictions in the results of various authors concerning the oxidation and autoxidation of adrenaline in an alkaline medium.

Novel Amperometric Biosensor Based on Tyrosinase/Chitosan Nanoparticles for Sensitive and Interference-Free Detection of Total Catecholamine.

The regulation of nervous and cardiovascular systems and some brain-related behaviors, such as stress, panic, anxiety, and depression, are strictly dependent on the levels of the main catecholamines of clinical interest, dopamine (DA), epinephrine (EP), and norepinephrine (NEP). Therefore, there is an urgent need for a reliable sensing device able to accurately monitor them in biological fluids for early diagnosis of the diseases related to their abnormal levels. In this paper, we present the first tyrosinase (Tyr)-based biosensor based on chitosan nanoparticles (ChitNPs) for total catecholamine (CA) detection in human urine samples. ChitNPs were synthetized according to an ionic gelation process and successively characterized by SEM and EDX techniques. The screen-printed graphene electrode was prepared by a two-step drop-casting method of: (i) ChitNPS; and (ii) Tyr enzyme. Optimization of the electrochemical platform was performed in terms of the loading method of Tyr on ChitNPs (nanoprecipitation and layer-by-layer), enzyme concentration, and enzyme immobilization with and without 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS) as cross-linking agents. The Tyr/EDC-NHS/ChitNPs nanocomposite showed good conductivity and biocompatibility with Tyr enzyme, as evidenced by its high biocatalytic activity toward the oxidation of DA, EP, and NEP to the relative o-quinone derivatives electrochemically reduced at the modified electrode. The resulting Tyr/EDC-NHS/ChitNPs-based biosensor performs interference-free total catecholamine detection, expressed as a DA concentration, with a very low LOD of 0.17 μM, an excellent sensitivity of 0.583 μA μM−1 cm−2, good stability, and a fast response time (3 s). The performance of the biosensor was successively assessed in human urine samples, showing satisfactory results and, thus, demonstrating the feasibility of the proposed biosensor for analyzing total CA in physiological samples.

Influence of a Constant Magnetic Field on the Mechanism of Adrenaline Oxidation

In order to establish the role of the magnetic effect in the key stages of the autoxidation and initiated oxidation radical-chain reactions, the experimental data and kinetic analysis of the influence of a magnetic field on the oxidative transformations of adrenaline are presented in this work. In the case of autoxidation, the process is being controlled by the rate of adrenaline consumption in the gross process of quinoid oxidation. The analysis of the obtained results is estimative and is based on the assumption of the leading role of superoxide radical during the autoxidation. Superoxide radical concentration increases with the increase in the applied magnetic field strength, which leads to the decrease in the rate of initiation of the quinoid process. In the case of initiated oxidation, the results obtained are based on the known radical-chain mechanism, and they were interpreted using the theory of radical pairs. The observed magnetic effect is explained by the influence of a constant magnetic field on the mechanism of chain termination of radical-chain oxidation and/or initiation of the autoxidation process.

Electrochemical determination of paracetamol at Cu doped ZnO/Nanoparticle with TX-100-surfactant MCPE: A cyclic voltammetric technique

Zinc oxide nanoparticles (ZnO/NPs) and Copper doped ZnO nanoparticles (Cu-ZnO/NPs) were prepared using the co-precipitation method and their characterizations were done with X-ray diffraction (XRD), Scanning electron microscope (SEM) and Energy dispersive spectroscopy (EDS) techniques. The prepared Cu-ZnO/NPs were used for the modification of the carbon paste electrode (CPE), the Cetyl Trimethyl Ammonium Bromide (CTAB) and Triton-X 100 (TX-100) surfactants were immobilization on the surface of Cu-ZnO/MCPE, the TX-100 modified electrode improved the more redox property with increasing the peak current for Paracetamol (PA) compare to Cu-ZnO/CTAB/MCPE. From the pH study confirms that the equal number of electrons and protons transfer mechanism involved at the MCPE. The cyclic voltammetry (CV) technique demonstrated the oxidation of both PA and Adrenaline (AD) was found to be adsorption controlled. The electrochemical response of PA and AD was linear in the µM concentration range and the limit of detection and limit of quantification was found to be 4.6 µM and 16.2 µM for PA and 3.9 µM and 13.2 µM for AD respectively, the effect of interference study was examined by using the differential pulse voltammetric technique (DPV), the Cu-ZnO/TX-100/MCPE shows an excellent selectivity towards PA in presence of different AD concentration. In present study commercial PA tablet also studied.

Synthesis of a sulfonated methylene blue-backboned polymer for biodetections

Poly (methylene blue) prepared by the widely used electrochemical polymerization method suffers from the undefined chemical structure and difficulty in modification with functional groups. The chemical polymerization of methylene blue is a challenging but attractive subject. We designed and prepared a methylene blue-backboned polymer (MBP-SO3) with the side chain modified with sulfonic acid groups. The polymer retains the redox activity of methylene blue and has a good mass transfer effect in electro-catalyzing the oxidation of dopamine, epinephrine, and uric acid. The negative charges carried by MBP-SO3 under physiological conditions are beneficial to attract cationic biomolecules, and its nanosheet-like morphology is conducive to charge transfer, which amplifies electrochemical signals in detection of target biomolecules. Using the Nafion film coating the electrode surface to block ascorbic acid and nicotinamide adenine dinucleotide (NADH), the MBP-SO3 modified electrode can selectively detect dopamine (0.02–25 mM), epinephrine (0.1–30 mM) and uric acid (0.03–3 mM) without interference from high-concentration of ascorbic acid and NADH solutions. The detections are also effective in serum samples. This work paves a way for methylene blue-backbone polymers in electrochemical sensing.

The effect of different GO reduction strategies on the lower level electrochemical determination of Epinephrine and Serotonin in quaternary mixtures

The effect of different reduction techniques on the structure and electrochemical sensing properties of reduced graphene oxide (RGO) was systematically studied. The comparison of the electrochemical properties of three RGOs formed by chemical reduction using sodium borohydride, hydrazine monohydrate and hydrothermal reduction was investigated. The electrodes modified with RGOs showed an excellent electrocatalytic effect by enhancing the anodic current and decreasing the electrode potential on the oxidation of epinephrine (EPN), and serotonin (SER). The effect of scan rate, pH, stability and reproducibility of the sensor was thoroughly investigated. Although all the RGOs obtained from different reduction strategies had very similar characteristics, NaBH4 reduced sample had better current response. The anodic peak current showed a linear relation with the EPN and SER concentration in a wide range of 70 nM-0.5 mM, 100 nM-2 mM respectively. The detection limit (LOD) of 0.33 nM and 3.99 nM were obtained for EPN and SER respectively. The modified electrode sensor was very effective for simultaneous determination of EPN, SER, Uric acid (UA) and Acetaminophen (AC) with well separated peaks at −0.069, 0.091, 0.269 and 0.395 V. The peak to peak separation values (ΔEpa) of EPN-AA, SER-EPN, AC-SER and AA-AC were 0.16, 0.178, 0.126, and 0.464 V. This work demonstrates the practical utility of the single component modified electrodes for measurements of EPN, SER in human blood serum and urine.