Solar graphene modified glassy carbon electrode for the voltammetric resolution and detection of dopamine, ascorbic acid and uric acid

An Efficient Enzyme-Less Uric Acid Sensor Development Based on PbO-Doped NiO Nanocomposites

Here, the voltammetric electrochemical approach was applied to detect uric acid (UA) in a conductive sensing medium (phosphate buffer solution-PBS) by using PbO-doped NiO nanocomposites (NCs)-decorated glassy carbon electrode (GCE) performing as working electrode. The wet-chemically prepared PbO-doped NiO NCs were subjected to characterization by the implementation of XRD, FESEM, XPS, and EDS analysis. The modified GCE was used to detect uric acid (UA) in an enzyme-free conductive buffer (PBS) of pH = 7.0. As the outcomes of this study reveal, it exhibited good sensitivity of 0.2315 µAµM−1cm−2 and 0.2233 µAµM−1cm−2, corresponding to cyclic (CV) and differential pulse (DPV) voltammetric analysis of UA, respectively. Furthermore, the proposed UA sensor showed a wider detection (0.15~1.35 mM) range in both electrochemical analysis methods (CV & DPV). In addition, the investigated UA sensor displayed appreciable limit of detection (LOD) of 41.0 ± 2.05 µM by CV and 43.0 ± 2.14 µM by DPV. Good reproducibility performance, faster response time and long-time stability in detection of UA were perceived in both electrochemical analysis methods. Finally, successful analysis of the bio-samples was performed using the recovery method, and the results were found to be quite acceptable in terms of accuracy. Thus, the findings indicate a reliable approach for the development of 5th generation biosensors using metal-oxides as sensing substrate to fulfill the requirements of portable use for in situ detection.

Solar Exfoliated Graphene Oxide: A Platform for Electrochemical Sensing of Epinephrine

Introduction:

In this study, solar exfoliated graphite oxide modified glassy carbon electrode was used for the anodic oxidation of epinephrine in a phosphate buffer medium at pH7. The modified electrode showed fast response and sensitivity towards Epinephrine Molecule (EP). The electrode was characterized electrochemically through Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV). Area of the electrode enhanced three times during modification and studies reveal that the oxidation process of EP occurs by an adsorption controlled process involving two electrons. The results showed a detection limit of 0.50 ± 0.01μM with a linear range up to 100 μM. The rate constant calculated for the electron transfer reaction is 1.35 s-1. The electrode was effective for simultaneous detection of EP in the presence of Ascorbic Acid (AA) and Uric Acid (UA) with well-resolved signals. The sensitivity, selectivity and stability of the sensor were also confirmed.

Methods:

Glassy carbon electrode modified by reduced graphene oxide was used for the detection and quantification of epinephrine using cyclic voltammetry and differential pulse voltammetry.

Results:

The results showed an enhancement in the electrocatalytic oxidation of epinephrine due to the increase in the effective surface area of the modified electrode. The anodic transfer coefficient, detection limit and electron transfer rate constant of the reaction were also calculated.

Conclusion:

The paper reports the determination of epinephrine using reduced graphene oxide modified glassy carbon electrode through CV and DPV. The sensor exhibited excellent reproducibility and repeatability for the detection of epinephrine and also its simultaneous detection of ascorbic acid and uric acid, which coexist in the biological system.

Recent Advances in Electrochemical and Optical Sensing of Dopamine

Nowadays, several neurological disorders and neurocrine tumours are associated with dopamine (DA) concentrations in various biological fluids. Highly accurate and ultrasensitive detection of DA levels in different biological samples in real-time can change and improve the quality of a patient's life in addition to reducing the treatment cost. Therefore, the design and development of diagnostic tool for in vivo and in vitro monitoring of DA is of considerable clinical and pharmacological importance. In recent decades, a large number of techniques have been established for DA detection, including chromatography coupled to mass spectrometry, spectroscopic approaches, and electrochemical (EC) methods. These methods are effective, but most of them still have some drawbacks such as consuming time, effort, and money. Added to that, sometimes they need complex procedures to obtain good sensitivity and suffer from low selectivity due to interference from other biological species such as uric acid (UA) and ascorbic acid (AA). Advanced materials can offer remarkable opportunities to overcome drawbacks in conventional DA sensors. This review aims to explain challenges related to DA detection using different techniques, and to summarize and highlight recent advancements in materials used and approaches applied for several sensor surface modification for the monitoring of DA. Also, it focuses on the analytical features of the EC and optical-based sensing techniques available.

Comparison of activation processes for 3D printed PLA-graphene electrodes: electrochemical properties and application for sensing of dopamine

This paper reports the comparison of the electrochemical properties of 3D PLA-graphene electrodes (PLA-G) under different activation conditions and through different processes.

Engineered Carbon-Nanomaterial-Based Electrochemical Sensors for Biomolecules

The study of electrochemical behavior of bioactive molecules has become one of the most rapidly developing scientific fields. Biotechnology and biomedical engineering fields have a vested interest in constructing more precise and accurate voltammetric/amperometric biosensors. One rapidly growing area of biosensor design involves incorporation of carbon-based nanomaterials in working electrodes, such as one-dimensional carbon nanotubes, two-dimensional graphene, and graphene oxide. In this review article, we give a brief overview describing the voltammetric techniques and how these techniques are applied in biosensing, as well as the details surrounding important biosensing concepts of sensitivity and limits of detection. Building on these important concepts, we show how the sensitivity and limit of detection can be tuned by including carbon-based nanomaterials in the fabrication of biosensors. The sensing of biomolecules including glucose, dopamine, proteins, enzymes, uric acid, DNA, RNA, and H2O2 traditionally employs enzymes in detection; however, these enzymes denature easily, and as such, enzymeless methods are highly desired. Here we draw an important distinction between enzymeless and enzyme-containing carbon-nanomaterial-based biosensors. The review ends with an outlook of future concepts that can be employed in biosensor fabrication, as well as limitations of already proposed materials and how such sensing can be enhanced. As such, this review can act as a roadmap to guide researchers toward concepts that can be employed in the design of next generation biosensors, while also highlighting the current advancements in the field.

Simultaneous determination of iron (II) and ascorbic acid in pharmaceuticas based on flow sandwich technique

The simple and easy performed flow system based on sandwich technique has been developed for the simultaneous separate determination of iron (II) and ascorbic acid in pharmaceuticals. The implementation of sandwich technique assumed the injection of sample solution between two selective reagents and allowed the carrying out in reaction coil two chemical reactions simultaneously: iron (II) with 1,10-phenanthroline and ascorbic acid with sodium 2,6-dichlorophenolindophenol. For achieving of excellent repeatability and considerable reagent saving the various parameters such as flow rate, sample and reagent volumes, reaction coil length were also optimized. The limits of detection (LODs) obtained by using the developed flow sandwich-type approach were 0.2 mg L(-1) for iron (II) and 0.7 mg L(-1) for ascorbic acid. The suggested approach was validated according to the following parameters: linearity and sensitivity, precision, recoveries and accuracy. The sampling frequency was 41 h(-1).

Nanomaterial-based electrochemical sensing of neurological drugs and neurotransmitters

Nanomaterial-modified detection systems represent a chief driver towards the adoption of electrochemical methods, since nanomaterials enable functional tunability, ability to self-assemble, and novel electrical, optical and catalytic properties that emerge at this scale. This results in tremendous gains in terms of sensitivity, selectivity and versatility. We review the electrochemical methods and mechanisms that may be applied to the detection of neurological drugs. We focus on understanding how specific nano-sized modifiers may be applied to influence the electron transfer event to result in gains in sensitivity, selectivity and versatility of the detection system. This critical review is structured on the basis of the Anatomical Therapeutic Chemical (ATC) Classification System, specifically ATC Code N (neurotransmitters). Specific sections are dedicated to the widely used electrodes based on the carbon materials, supporting electrolytes, and on electrochemical detection paradigms for neurological drugs and neurotransmitters within the groups referred to as ATC codes N01 to N07. We finally discuss emerging trends and future challenges such as the development of strategies for simultaneous detection of multiple targets with high spatial and temporal resolutions, the integration of microfluidic strategies for selective and localized analyte pre-concentration, the real-time monitoring of neurotransmitter secretions from active cell cultures under electro- and chemotactic cues, aptamer-based biosensors, and the miniaturization of the sensing system for detection in small sample volumes and for enabling cost savings due to manufacturing scale-up. The Electronic Supporting Material (ESM) includes review articles dealing with the review topic in last 40 years, as well as key properties of the analytes, viz., pKa values, half-life of drugs and their electrochemical mechanisms. The ESM also defines analytical figures of merit of the drugs and neurotransmitters. The article contains 198 references in the main manuscript and 207 references in the Electronic Supporting Material. Figureᅟ

Graphene and its nanocomposite material based electrochemical sensor platform for dopamine

In this review, the recent progress in the electrochemical sensing of dopamine with various graphene and their nanocomposite materials modified electrodes are presented.