A simple sensing approach for the determination of dopamine by poly (Yellow PX4R) pencil graphite electrode

Conductive PEDOT:PSS copolymer electrode coatings for selective detection of dopamine in ex vivo mouse brain slices

A novel voltammetric sensor was developed to selectively determine dopamine (DA) concentration in the presence of ascorbic acid (AA) and 3,4-dihydroxyphenylacetic acid (DOPAC). This sensor utilizes a modified pencil graphite electrode (PGE) coated with a newly synthesized poly (3,4-ethylene dioxythiophene) (PEDOT):poly (styrene sulfonate-co-2-(3-(6-Methyl-4-oxo-1,4-dihydropyrimidin-2-yl) ureido) ethyl methacrylate) (P(SS-co-UPyMA)) composite. The PEDOT:P(SS-co-UPyMA) (PPU) composite was characterized using nuclear magnetic resonance, X-ray photoelectron, and Raman spectroscopies. The PPU-coated PGE was characterized using electrochemical techniques, including cyclic and differential pulse voltammetry. Compared to uncoated, PPU-coated PGE demonstrated improved sensitivity and selectivity for DA. The sensor exhibited a dynamic linear range of 0.1-300 μM for DA, with a detection limit of 44.4 nM (S/N = 3). Additionally, the PPU-coated PGE showed high reproducibility and storage stability for four weeks. To demonstrate its practical applicability, the PPU-coated PGE sensor was used for ex vivo brain slice samples from control and Parkinson's disease model mice.

Edge and Basal Plane Anisotropy of a Preanodized Pencil Graphite Electrode Surface Revealed Using Scanning Electrochemical Microscopy and Electrocatalytic Dopamine Oxidation as a Molecular Probe

Pencil graphite (PGE), an ultralow-cost and ready-to-use disposable-type electrode, has been used for various electrochemical and electroanalytical applications after its surface anodization (PGE*, * means preanodized surface). Indeed, systematic studies on mechanistic and surface features of PGE* have not yet been explored. Herein, we report anodized pencil graphite as a model system to study molecular level insights into the surface using a scanning electrochemical microscopy (SECM) technique and dopamine (DA) electrocatalytic oxidation reaction as a molecular probe. The as-prepared PGE* showed an appreciable electronic conductivity similar to the edge-plane graphitic sites (EPPG) of the highly pyrolytic graphitic electrode (HOPG) but without any surface deterioration that occurs with HOPG due to the instability of the EPPG. Physicochemical characterizations by FESEM, FTIR, Raman, and XPS techniques revealed a flake-like exfoliated PGE* surface with higher contents of carbon-oxygen especially phenolic/alcoholic functional groups than the PGE surface. Based on the chronocoulometric experiment, the number of functional groups formed on the PGE* was calculated as 10.9 × 10-10 mol cm-2. An independent SECM technique using ferricyanide as a redox probe showed the existence of a heterogeneous surface and exhibited an improved electron transfer activity due to the flake-like graphitic island on the PGE* surface. Investigated DA electrochemical oxidation on PGE* yielded about three times enhancement in the peak current signal and about 200 mV reduction in the oxidation potential over the PGE without any serious surface fouling feature that is related to the intermediate polydopamine formation on the basal-plane graphitic surface of the underlying electrode. As an independent electroanalytical study, a prototype electrochemical sensor using PGE* as a working electrode for instant detection of DA-containing pharmaceutical samples in a 1 mL Eppendorf vial has been demonstrated.

Surface-Activated Pencil Graphite Electrode for Dopamine Sensor Applications: A Critical Review

Pencil graphite electrode (PGE) is an alternative, commercially available, ready-to-use, screen-printed electrode for a wide range of electroanalytical applications. Due to the complex-matrix composition and unpredictable electro-inactive nature of PGE in its native form, a surface pre-treatment/activation procedure is highly preferred for using it as an electroactive working electrode for electroanalytical applications. In this article, we review various surface pre-treatment and modification procedures adopted in the literature with respect to the sensitive and selective detection of dopamine as a model system. Specific generation of the carbon-oxygen functional group, along with partial surface exfoliation of PGE, has been referred to as a key step for the activation. Based on the Scopus^® index, the literature collection was searched with the keywords "pencil and dopamine". The obtained data were segregated into three main headings as: (i) electrochemically pre-treated PGE; (ii) polymer-modified PGEs; and (iii) metal and metal nanocomposite-modified PGE. This critical review covers various surface activation procedures adopted for the activation for PGE suitable for dopamine electroanalytical application.

Poly (red DSBR)/Al-ZnO modified carbon paste electrode sensor for dopamine: a voltammetric study

In the present work, the ZnO and Al-ZnO nanoflakes (NFs) were synthesized by the co-precipitation process. The synthesized NFs were characterized by X-ray diffraction and field emission scanning electron microscopy. Energy dispersive X-ray spectrometer was explored for the elemental chemical compositions. The prepared NFs were taken for the modification of the electrode and developed the modified electrode for the electrochemical analysis of the dopamine (DOA) at pH 7.4. The Al-ZnO modified carbon paste electrode (MCPE) was electropolymerised by using textile dye red DSBR. The Po-RD/Al-ZnO MCPE exhibited good electrochemical sensor properties towards the electrochemical detection of DOA. Several factors such as the impact of speed rate (υ), pH and concentration of the DOA were analyzed at the modified electrode. The great sensitivity was established to the fast electron-transfer kinetics and surface coverage of the DOA on the electrode. The prepared electrode exhibits satisfactory stability at the ambient conditions. The detection limit of 0.58 μM was achieved for the DOA. The decorated sensor was stable, sensitive, selective, and reproducible and used in the analytical applications.

Murexide-derived in vitro electrochemical sensor for the simultaneous determination of neurochemicals

This work highlights the protocol employed for the simultaneous electroanalysis of tryptamine, serotonin and dopamine using a conducting poly-murexide-based electrode. To date, this is the first-of-its-kind report of simultaneous electrochemical determination of these three targets. Features of the developed electrode were identified by employing FE-SEM analysis. Under optimized conditions, the analytes underwent an irreversible electro-oxidation at the modified electrode surface, with a linear range of 0.5-40 μΜ, 0.4-40.4 μΜ and 0.5-40 μΜ for dopamine, serotonin and tryptamine, respectively. The electrolytic medium employed for the sensing was a phosphate-buffered solution with pH 7. The specificity of the developed electrode was also satisfactory in the presence of other biomolecules including L-phenylalanine, L-serine, glucose and ascorbic acid. Thus, the developed murexide-derived conducting-polymer-based electrode was used for the simultaneous sensing of the neurochemicals dopamine, serotonin and tryptamine. Electroanalysis was also demonstrated for these targets in human serum.