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Catecholamine precursors and metabolites are emerging as a prominent biomarker for the prognosis and diagnosis of many pathological conditions. This article details the fabrication, features and efficacy of the voltammetric sensor based on copper nanoparticles (CuNP)-decorated poly-3-Amino-5-mercapto-1,2,4-triazole-modified glassy carbon electrode p(Cu-AMT/GCE) for the individual and simultaneous determination of L-Dopa and Vanillylmandelic acid (VMA). The modified electrode has been characterised via different analytical techniques. The CuNP-decorated polymeric film enabled the formation of well-defined and well-separated oxidation peaks for the analytes with a limit of detection 6.80 × 10–8 mol L−1 and 9.90 × 10–8 mol L−1, respectively, for L-Dopa and VMA. Scan rate studies reveal the involvement of a reversible two electron–two proton reaction for the electrooxidation of L-Dopa and an irreversible, one electron–one proton reaction for VMA on p(Cu-AMT/GCE). The credibility of the sensor was ascertained from reproducibility, repeatability and stability studies. The satisfactory results obtained from the interference studies and adequate recovery values achieved from spike recovery analysis in synthetic physiological fluids substantiate the practical applicability of the sensor. [ABSTRACT FROM AUTHOR]

A voltammetric sensor has been developed for dopamine and tyrosine based on the double modification of polycalconcarboxylic acid (pCCA) and electrochemically reduced graphene oxide (ERGO) on the glassy carbon electrode (GCE). The electrode was first modified with calconcarboxylic acid, followed by the modification with electrochemically reduced graphene oxide (ERGO/pCCA/GCE) over it. The extended п-electron system on pCCA helps to increase the conductivity of the material. The functional groups present on pCCA along with its extended conjugation increase the electrocatalytic effect of the modified electrode. ERGO has good electrochemical properties due to the reduction of oxygen-containing functional groups in their edge plane sites. Rapid electron transfer is possible in the case of ERGO-modified electrodes due to the high proportion of the edge plane defects. When pCCA and ERGO are clubbed together, there will be a synergistic effect of the properties of these two materials. Characterisation studies have been done, and different sensor parameters were optimised. Under optimal experimental conditions, a wide linear range was obtained for the determination of dopamine from 1.00 × 10−5 M to 5.00 × 10−7 M. The determination of tyrosine was possible in two linear ranges, from 7.00 × 10−5 M to 2.00 × 10−5 M and from 1.00 × 10−5 M to 3.00 × 10−6 M. The limit of detection values (LODs) obtained for dopamine and tyrosine were 1.00 × 10−7 M and 9.00 × 10−7 M. Application studies for the determination of the analytes were done in synthetic urine and blood serum using the spike recovery method. The electrochemical sensing of DA and Tyr using ERGO/pCCA/GCE [ABSTRACT FROM AUTHOR]

Monoamine neuromodulators norepinephrine (NE) and octopamine (OA) have been discovered to coexist and are associated with neurological and cardiovascular pathology. Here, we have developed a voltammetric sensor to determine NE and OA individually as well as simultaneously using an eco-friendly and cost-effective amino acid modifier, tyrosine (Tyr), which possesses favourable adsorption sites for the binding of these analytes. At poly-Tyr modified glassy carbon electrode (p-Tyr/GCE), the neuromodulators exhibited increased current response at lower overpotential than at the bare GCE. The submicromolar determination of these neuromodulators on p-Tyr/GCE was demonstrated in linear dynamic ranges (LDR) over 7.00 × 10−6–1.00 × 10−6 M and 9.00 × 10−7–1.00 × 10−7 M for NE and over the ranges 1.00 × 10−5–2.00 × 10−6 M and 1.00 × 10−6–2.00 × 10−7 M for OA with the detection limits of 1.37 × 10−8 M and 4.74 × 10−8 M for NE and OA, respectively. The mechanistic aspects were studied and the electro-oxidation of NE and OA on p-Tyr/GCE was found to be two electrons, two-proton transfer reaction. The utility of the proposed method was validated by the determination of NE in pharmaceutical formulations. [ABSTRACT FROM AUTHOR]

The present work describes development of a simple and selective voltammetric sensor for the simultaneous determination of three DNA bases guanine (Gua), adenine (Ade) and thymine (Thy). The proposed poly(L-arginine)-electrochemically reduced graphene oxide modified glassy carbon electrode [p(L-arg)-ERGO/GCE)] exhibited well-resolved and well-defined peaks for the electro-oxidation of these DNA bases with an enhancement in peak current and reduction in peak potential, compared to bare electrode. The electro-catalytic efficiency might be due to the synergistic electro-catalytic effect of L-arginine and reduced graphene oxide. For simultaneous determination, the peak currents of Gua, Ade and Thy showed linear variations in the concentration range 1.00 × 10–4 – 3.00 × 10–6 M, 1.00 × 10–4 – 3.00 × 10–6 M and 1.00 × 10–4 – 1.00 × 10–5 M, respectively. Mechanistic aspects of the electro-oxidation of Gua, Ade and Thy on the surface of p(L-arg)-ERGO/GCE have been explored. The proposed sensor also displayed good selectivity toward Gua, Ade and Thy without any considerable interferences from coexisting species. The applicability of the proposed sensor was demonstrated by simultaneously determining the concentration of Gua, Ade and Thy in the spiked urine and blood serum samples with satisfactory results. [ABSTRACT FROM AUTHOR]

The present article reports the efficiency of L-cysteine modulated copper nanoclusters (L-cys-CuNCs) as a fluorescent probe for the selective determination of naturally occurring bile pigments biliverdin (BVD) and bilirubin (BLR). These pigments were found to quench the fluorescence of L-cys-CuNCs through static processes. Under optimized conditions, the proposed strategy permitted the quantification of BVD and BLR in the range 4.00 × 10−5 to 5.00 × 10−7M and 1.00×10−5 to 1.00×10−6 M respectively with limits of detection 2.33 × 10−7M and 2.29 × 10−7 M. The practical utility of the developed sensor have been investigated in spiked blood and urine samples. [ABSTRACT FROM AUTHOR]

Introduction: Litsea glutinosa (Lour.) C.B.Rob., is an aromatic medicinal tree belongs to the family Lauraceae and rarely distributed in the Western Ghats. Ethnomedicinally, the bark is used by the traditional practitioners as a demulcent, emollient and in the treatment of diarrhea and dysentery, and to facilitate wound healing process. The leaf paste is applied to relieve respiratory diseases; cough and also used as a demulcent and an emollient. Methods: The petroleum ether, chloroform and ethanol extracts of stem bark and leaf were screened for potential antibacterial activity using agar well diffusion method against 8 clinical strains isolated from infectious sources belonging to Gram-positive Staphylococcus aureus, Bacillus stubtilis and gram-negative Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella typhi, Salmonella paratyphi and Proteus sp. Minimum Inhibitory Concentration (MIC) of the three sequential extracts of the leaf and stem bark was carried out against clinical isolated strains using two fold agar dilution method. Results: Ethanol extract of stem bark exhibited significant antibacterial activity with 2.5mg/ml MIC against Bacillus subtilis (19.20 ± 1.52), Escherichia coli (16.40 ± 0.55) and Staphylococcus aureus (15.20 ± 0.84) indicating the potent drug for the treatment of diarrhea and dysentery. Among the tree sequential extracts of the leaf the ethanol extract showed potent antibacterial activity against Klebsiella pneumoniae (16.40 ± 0.80) and may acting as a suitable drug for respiratory disorders. Conclusion: The obtained results justify the ethnomedicinal claims of Litsea glutinosa. [ABSTRACT FROM AUTHOR]

The fabrication and electrochemical response characteristics of two novel potentiometric sensors for the selective determination of domperidone (DOM) are described. The two fabricated sensors incorporate DOM–PTA (phosphotungstic acid) ion pair as the electroactive material. The sensors include a PVC membrane sensor and a carbon paste sensor. The sensors showed a linear, stable, and near Nernstian slope of 56.5 and 57.8 mV/decade for PVC membrane and carbon paste sensors, respectively over a relatively wide range of DOM concentration (1.0 × 10−1–1.0 × 10−5 and 1.0 × 10−1–3.55 × 10−6 M). The response time of DOM–PTA membrane sensor was less than 25 s and that in the case of carbon paste sensor was less than 20 s. A useful pH range of 4–6 was obtained for both types of sensors. A detection limit of 7.36 × 10−5 M was obtained for PVC membrane sensor and 1.0 × 10−6 M was obtained for carbon paste sensor. The proposed sensors showed very good selectivity to DOM in the presence of a large number of other interfering ions. The analytical application of the developed sensors in the determination of the drug in pharmaceutical formulations such as tablets was investigated. The results obtained are in good agreement with the values obtained by the standard method. The sensors were also applied for the determination of DOM in real samples such as urine by the standard addition method. [ABSTRACT FROM AUTHOR]

A metalloporphyrin incorporated carbon paste sensor has been developed for the determination of metronidazole benzoate (MTZB). Zn(II) complex of 5,10,15,20-tetrakis (3-methoxy-4-hydroxy phenyl) porphyrin (TMHPP) was used as the active material. The MTZB gave a well-defined reduction peak at-0.713 V in 0.1 mol l-1 phosphate buffer solution of pH around 7. Compared with bare carbon paste electrode (CPE), the TMHPP Zn(II) modified electrode significantly enhanced the reduction peak current of MTZB as well as lowered its reduction potential. Under optimum conditions the reduction peak current was proportional to MTZB concentration over the range 1 × 10-3 mol l-1 to 1 × 10-5 mol l-1. The detection limit was found to be 4.36 × 10-6 mol l-1. This sensor has been successfully applied for the determination of MTZB in pharmaceutical formulations and urine samples. [ABSTRACT FROM AUTHOR]