A voltammetric biosensor based on poly(o-methoxyaniline)-gold nanocomposite modified electrode for the simultaneous determination of dopamine and folic acid.

Dopamine (DA) and Folic acid (FA) are co-existing compounds in biological fluids that plays a vital role in central nervous system and human metabolism. DA is an important neurotransmitter in the brain's neural circuits and its diminution often results in Parkinson's disease. Folate is another form of folic acid, which is known as one of the B vitamins. It is utilized as an additive by women during pregnancy in order to prevent the neural tube defects. The present study reports on the fabrication of electrochemical sensor for the simultaneous determination of DA and FA using poly(o-methoxyaniline)-gold (POMA-Au) nanocomposite. The POMA-Au nanocomposite was prepared via insitu chemical oxidative polymerization method and characterized using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The suitability of POMA-Au nanocomposite as a modifier for the electrocatalytic detection of DA and FA in aqueous solution was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA) techniques. The fabricated POMA-Au/GCE sensor exhibited sharp and intense peaks towards the electro-oxidation of DA and FA as compared to bare electrode. The sensor exhibited the promising electron mediating behavior with well separated oxidation peaks with a potential difference of about 350.0 mV. The linear calibration plots of DA and FA were obtained from 10.0 to 300.0 µM and 0.5 to 900.0 µM with the detection limits of 0.062 µM and 0.090 µM, respectively. The reliability of this sensor was verified to be precise as well as sensitive for the determination of DA and FA in pharmaceutical samples and human urine samples.

A strategy to promote the electroactive platform adopting poly(o-anisidine)-silver nanocomposites probed for the voltammetric detection of NADH and dopamine.

A study on the voltammetric detection of NADH (ß-nicotinamide adenine dinucleotide), Dopamine (DA) and their simultaneous determination is presented in this work. The electrochemical sensor was fabricated with the hybrid nanocomposites of poly(o-anisidine) and silver nanoparticles prepared by simple and cost-effective insitu chemical oxidative polymerization technique. The nanocomposites were synthesized with different (w/w) ratios of o-anisidine and silver by increasing the amount of o-anisidine in each, by keeping silver at a fixed quantity. The XRD patterns revealed the semi-crystalline nature of poly(o-anisidine) and the face centered cubic structure of silver. The presence of silver in its metallic state and the formation of nanocomposite were established by XPS analysis. Raman studies suggested the presence of site-selective interaction between poly(o-anisidine) and silver. HRTEM studies revealed the formation of polymer matrix type nanocomposite with the embedment of silver nanoparticles. The sensing performance of the materials were studied via cyclic voltammetry, differential pulse voltammetry and chronoamperometry techniques. Fabricated sensor with 3:1 (w/w) ratio of poly(o-anisidine) and silver exhibited good catalytic activity towards the detection of NADH and DA in terms of potential and current response, when compared to others. Several important electrochemical parameters regulating the performance of the sensor have been evaluated. Under the optimum condition, differential pulse voltammetry method exhibited the linear response in the range of 0.03 to 900µM and 5 to 270µM with a low detection limit of 0.006µM and 0.052µM for NADH and DA, respectively. The modified electrodes exhibited good sensitivity, stability, reproducibility and selectivity with well-separated oxidation peaks for NADH and DA in the simultaneous determination of their binary mixture. The analytical performance of the nanocomposite as an electrochemical sensor was also established for the determination of NADH in human urine and water samples and DA in pharmaceutical dopamine injections with satisfactory coverage.

Investigations on the performance of poly(o-anisidine)/graphene nanocomposites for the electrochemical detection of NADH.

The electrocatalytic oxidation of dihydronicotinamide adenine dinucleotide (NADH) based on poly(o-anisidine)/graphene (POA/GR) nanocomposites modified glassy carbon electrode (GCE) was explored for the first time. POA/GR nanocomposites were synthesized via chemical oxidative polymerization method. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and UV-Vis spectroscopy results demonstrate that nanocomposites are successfully synthesized. An intriguing composite structure was observed using different ratios of o-anisidine monomer and graphene. The electrical properties and electrochemical properties of these nanocomposites are investigated by impedance spectroscopy technique and cyclic voltammetric (CV) method, respectively. The synthesized nanocomposites were used to modify glassy carbon electrode (GCE), and the modified electrodes were found to exhibit electrocatalytic activity for oxidation of NADH at low potential range of +0.045 V in a neutral environment. The fabricated sensor based on POA/GR31-modified GCE exhibited enhanced current response with very high sensitivity of 47.1 µA µM(-1) for the detection of NADH. The developed POA/GR-modified GCE exhibited excellent reproducibility, stability, and selectivity for the determination of NADH. The practical analytical utility of the proposed method was demonstrated by NADH spiked ascorbic acid (AA) and the results confirmed that the proposed method is suitable for the determination of NADH in the presence of AA. This can open up new opportunities for simple and selective detection of NADH and provide a promising platform for biosensor designs.