Overoxidized polyimidazole/graphene oxide copolymer modified electrode for the simultaneous determination of ascorbic acid, dopamine, uric acid, guanine and adenine

Flexible and conductive titanium carbide-carbon nanofibers for the simultaneous determination of ascorbic acid, dopamine and uric acid

The development of novel materials for facile, cost-effective and quick practical application is a demanding research interest in electroanalytical chemistry. Titanium carbide (TiC), as one of the most important transition metal carbides, exhibits good chemical stability and electrical conductivity, and its electrocatalytic activity resembles that of metals, but is much cheaper. In this work, TiC nanoparticle (NP) loaded carbon nanofiber (CNF) films (TCNFs) are synthesized using an electrospinning and carbothermal technique, which facilely maintains their structural integrity with robust adhesion. Uniform TiC NPs are firmly embedded in the surface of CNFs, which integrates the large surface area and unique 3D, porous network structure of CNFs with the good conductivity and excellent electrocatalytic activity of TiC NPs. Simultaneous electrochemical sensing of ascorbic acid (AA), dopamine (DA) and uric acid (UA) at TCNFs displays excellent peak current signals with well-defined peak potentials. The linear ranges are 0.001-1.5 mM, 0.05-160 μM and 0.001-0.875 mM for AA, DA and UA, and the corresponding detection limits are 0.3 μM, 20 nM and 0.3 μM, respectively. In addition, TCNFs show long-term sensing stability and potential applications in real samples, and behave as good anti-interference agents towards KNO₃, ZnSO₄, glucose, etc. Most importantly, unlike some common carbon-based electrochemical sensor systems, an adsorption-less response is observed for the test analytes at the TCNF electrode. TCNFs show interesting potential as candidates for the construction of electrochemical sensors.

Poly(glycine)/graphene oxide modified glassy carbon electrode: Preparation, characterization and simultaneous electrochemical determination of dopamine, uric acid, guanine and adenine

A novel poly(glycine) (p-GLY)/graphene oxide (GO) composite based sensor (p-GLY/GO) was successfully prepared on glassy carbon electrode by simple electropolymerization. Electrochemical responses of analytes on p-GLY/GO modified electrode were studied by cyclic voltammetry and differential pulse voltammetry. The results demonstrated that p-GLY/GO modified electrode showed a favorable application for the simultaneous determination of dopamine (DA), uric acid (UA), guanine (GU) and adenine (AD). Owing to the synergistic effect of p-GLY and GO, the oxidation peaks of four analytes separated well from each other, and the potential separations of oxidation peaks of DA-UA, UA-GU and GU-AD were large up to 170, 350 and 300 mV, respectively. As-prepared p-GLY/GO modified electrode offered wide linear responses for DA, UA, GU and AD over the ranges of 0.20-62, 0.10-105, 0.15-48 and 0.090-103 μM with detection limits of 0.011, 0.061, 0.026 and 0.030 μM (S/N = 3), respectively. Moreover, p-GLY/GO modified electrode presented favorable selectivity, stability and reproducibility, which was a promising candidate as an electrochemical sensor for the simultaneous determination of DA, UA, GU and AD.

Simultaneous voltammetric determination of guanine and adenine by using a glassy carbon electrode modified with a composite consisting of carbon quantum dots and overoxidized poly(2-aminopyridine)

A composite consisting of carbon quantum dots (CQDs) and overoxidized poly(2-aminopyridine) (PAPox) was deposited on a glassy carbon electrode (GCE) through electrochemical polymerization and electrochemical oxidation. The modified GCE was used for the simultaneous determination of guanine and adenine. Electrochemical responses to guanine and adenine were investigated by cyclic voltammetry and differential pulse voltammetry. Owing to the synergistic effect of CQDs and PAPox, two oxidation peaks can be observed, with peaks at 0.81 and 1.13 V (vs. SCE) for guanine and adenine, respectively. The current at the respective peaks has a linear dependence on the concentrations of guanine in the range from 1.0 to 65 μM, and of adenine in the range from 2.0 to 70 μM. The respective detection limits are 0.51 and 0.39 μM (at an S/N ratio of 3). The modified GCE is selective, reproducible and stable. Graphical abstract Schematic of the preparation of a glassy carbon electrode modified with carbon quantum dots and overoxidized poly(2-aminopyridine (CQD/PAPox/GCE), and its application for the simultaneous determination of guanine and adenine.

An efficient electrode for simultaneous determination of guanine and adenine using nano-sized lead telluride with graphene

Herein, lead telluride (PbTe) nanocrystals were chemically synthesized at room temperature via reduction of homogeneous mixtures of tartrate complexes of Pb²⁺ and Te⁴⁺ with sodium borohydride.

Small biomolecule sensors based on an innovative MoS2–rGO heterostructure modified electrode platform: a binder-free approach

Hydrothermally synthesized MoS₂–rGO nanoflowers can simultaneously sense ascorbic acid (AA), dopamine (DA) and uric acid (UA) with good separating peak-to-peak potentials.

Functional Properties of Lupinus angustifolius Seed Protein Isolates

Protein isolates prepared by alkaline solubilization followed by isoelectric precipitation and freeze-drying from six varieties of Lupinus angustifolius (Haags Blaue, Sonate, Probor, Borlu, Boregine, and Boruta) grown in Mexico were evaluated for functional properties: nitrogen solubility, water-holding capacity (WHC), oil holding capacity (OHC), emulsion activity index (EAI), emulsion stability index (ESI), foaming capacity (FC), foam stability (FS), and gelling minimum concentration (GMC). The nitrogen solubility values, WHC, OHC, and FC did not show significant differences between the protein isolates. The solubility of the isolates was minimal at pH of 4.0 and 5.0 while the regions of maximum solubility were found at pH of 2.0 and 10.0. There were significant differences in EAI and ESI depending on the varieties used. The isolates of the Boregine and Borlu varieties showed the highest EAI with 29.3 and 28.3 m2 g−1, respectively, while the lowest index was recorded in the isolate obtained from the Sonate variety (24.6 m2 g−1). Like solubility, these indices also increased at both extremes of pH evaluated; both properties were minimal in the isoelectric pH range (4.0 to 5.0).

Surfactant-free synthesis of three-dimensional nitrogen-doped hierarchically porous carbon and its application as an electrode modification material for simultaneous sensing of ascorbic acid, dopamine and uric acid

A 3D N-doped hierarchically porous carbon modified electrode enables simultaneous sensitive detection of ascorbic acid, dopamine and uric acid.

Constructing a novel 8-hydroxy-2'-deoxyguanosine electrochemical sensor and application in evaluating the oxidative damages of DNA and guanine

8-Hydroxy-2'-deoxyguanosine (8-OHdG) is commonly identified as a biomarker of oxidative DNA damage. In this work, a novel and facile 8-OHdG sensor was developed based on the multi-walled carbon nanotubes (MWCNTs) modified glassy carbon electrode (GCE). It exhibited good electrochemical responses toward the oxidation of 8-OHdG, and the linear ranges were 5.63×10(-8)-6.08×10(-6)M and 6.08×10(-6)-1.64×10(-5)M, with the detection limit of 1.88×10(-8)M (S/N=3). Moreover, the fabricated sensor was applied for the determination of 8-OHdG generated from damaged DNA and guanine, respectively, and the oxidation currents of 8-OHdG increased along with the damaged DNA and guanine within certain concentrations. These results could be used to evaluate the DNA damage, and provide useful information on diagnosing diseases caused by mutation and deficiency of the immunity system.

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.

Selective electrochemical detection of dopamine in the presence of uric acid and ascorbic acid based on a composite film modified electrode

An electrochemical dopamine sensor based on vanadium-substituted polyoxometalates, copper oxide and chitosan–palladium was fabricated by the LBL technique.

Simultaneous determination of guanine and adenine in the presence of uric acid by a poly(para toluene sulfonic acid) mediated electrochemical sensor in alkaline medium

Simultaneous sensing of guanine and adenine in presence of uric acid in alkaline medium by polymer modified electrode.

Facile synthesis of 3D porous nitrogen-doped graphene as an efficient electrocatalyst for adenine sensing

We demonstrate a simple, low-cost and eco-friendly strategy for the convenient preparation of three-dimensional porous nitrogen-doped graphene (3D-N-GN) for the highly sensitive detection of adenine.

Electrochemical sensing of guanine, adenine and 8-hydroxy-2′-deoxyguanosine at glassy carbon modified with single-walled carbon nanotubes covalently functionalized with lysine

Synthesis and characterization of l-lysine covalently functionalized SWCNT and analytical application for the highly sensitive quantification of guanine, adenine and 8-hydroxy-2′-deoxyguanosine.

Simultaneous Determination of Dopamine, Uric Acid and Guanine at Polyadenine Film Modified Electrode

A polyadenine film (PAE) modified glassy carbon electrode (GCE) was employed for the simultaneous determination of dopamine (DA), uric acid (UA) and guanine (GA). Experimental results showed that this modified electrode had good electrocatalytic properties for the oxidation of DA, UA and GA. Under optimal conditions, DA, UA and GA reflected their electrochemical response into three separated and well-defined oxidation peaks, whose currents increased 47-, 12-, and 7-fold, respectively, compared with those at bare electrode. Moreover, their oxidation peak currents were linear proportional to their concentrations within the ranges of 2.5 - 75, 10 - 750, and 7.5 - 75 μmol L(-1), respectively, and the limits of detection (LOD) (S/N = 3) were 0.075, 0.35, and 0.025 μmol L(-1), respectively. Compared with a variety of modified electrodes, this designed sensor had a wider linear range and lower LOD. Furthermore, the sensor exhibited good stability and reproducibility.