Oxidation Of Dopamine Research Articles

Palladium nanoparticles decorated Ni-MOF nanocomposite as an electrochemical platform for the selective detection of dopamine

In this study, we prepared an electrochemical sensor using palladium nanoparticles decorated nickel-based metal–organic framework (Pd@Ni-MOF) nanocomposite for the detection of dopamine. The cyclic voltammetry analysis proved that a glassy carbon electrode modified by the Pd@Ni-MOF nanocomposite showed good electrocatalytic activity toward dopamine oxidation. Differential pulse voltammetry showed that the peak current increased linearly with dopamine concentration in the range of 1 nM to 100 μM with a low detection limit of 0.01 μM. The nanocomposite sensor exhibited good selectivity, stability, and excellent reproducibility. The sensor is used to determine the dopamine level in urine samples with acceptable recovery, implying its feasibility for practical application.

Carbon fiber microelectrode array loaded with the diazonium salt-single-walled carbon nanotubes composites for the simultaneous monitoring of dopamine and serotonin in vivo

Carbon fiber microelectrode arrays based on diazonium salt and single-walled carbon nanotubes composites (DS-SWCNT/CFMEA) have been fabricated, and it developed for the simultaneous monitoring of dopamine (DA) and serotonin (5-HT) with differential pulse voltammary (DPV). The diazonium salt can improve the water-solubility of single-walled carbon nanotubes and show good selectivity to DA, thus DS-SWCNT/CFMEA exhibits enhanced electrocatalytic activity for the oxidation of DA and 5-HT, and well antifouling ability to the other biomolecules. Moreover, DS-SWCNT/CFMEA shows the wider liner range, and the good performance of precision, reproducibility and biocompatibility. The excellent characteristics of the prepared microsensor array make it to be used to monitor the release of DA and 5-HT in the mouse brain striatum of different group over time. Meanwhile, the results of in vivo on line assay further confirmed the pharmacological effects of Uncaria alkaloid extract solution on DA and 5-HT. This research may provide a new method for monitoring the release of neurobiomolecules, and the microsensor array are expected to be a tool for the study of pharmacological and physiological processes on line in vivo.

Rationally designed f-MWCNT-coated bismuth molybdate (f-MWCNT@BMO) nanocomposites for the voltammetric detection of biomolecule dopamine in biological samples.

Selective and sensitive dopamine (DPA) sensor was developed using hydrothermally prepared functionalized multi-walled carbon nanotube-coated bismuth molybdate (f-MWCNT@BMO). The f-MWCNT@BMO-reinforced electrode exhibited an outstanding electrocatalytic activity towards DPA oxidation. The nanocomposite-reinforced electrode displayed a rapid response towards DPA sensing and possessed the minimized potential of (Epa + 0.285V vs Ag/AgCl) in 0.1M phosphate buffer (PB). Theelectrochemical results of prepared sensors were analyzed using the differential pulse voltammetry method (DPV). As a result, the f-MWCNT@BMO-reinforced electrode exhibited a widelinear range of 10nM-814μM with a very low detection limit of 3.4nM towards DPA oxidation. The developed sensor shows excellent selectivity in presence of similar functional group biomolecules. Thedetection of DPA in real samples was evaluated in human serum, as the results of the proposed sensor possessed good recoveries.

Systematic Study on Morphological, Electrochemical Impedance, and Electrocatalytic Activity of Graphitic Carbon Nitride Modified on a Glassy Carbon Substrate from Sequential Exfoliation in Water.

Several researchers have synthesized graphitic carbon nitride (GCN) from various precursors and attached it to electrode substrates after exfoliation under different conditions and have reported inconsistent data on electrochemical impedance, electroactive surface areas, and electrocatalytic activity. Thus, the present study aims to study the same systematically in addition to morphology after modifying GCN on the GC substrate from different exfoliation times in water assisted by sonication. The GCN was prepared from urea by bulk condensation pyrolysis and then attached to the GC substrate by drop casting to study its morphology, electrochemical impedance, and electrocatalytic activity with respect to exfoliation. The SEM image of a GCN-modified GC plate after 15 and 30 min of exfoliation shows bulky structure whereas thin sheets of GCN were noticed after 120 min of exfoliation. On the other hand, broken sheets were observed when GCN was coated from beyond 120 min of exfoliation. The electrochemical impedance studies show that the charge transfer resistance (RCT) of GCN modified from 15 and 30 min of exfoliation was higher than that for the bare GC electrode. However, it started to decrease while increasing the exfoliation time, and 1.8 kΩ was obtained after 120 min of exfoliation. The RCT value was again increased to 3.2 and 5.0 kΩ for GCN coated after 150 and 180 min of exfoliation, respectively. The electroactive surface area (EASA) of GCN modified by 15 and 30 min of exfoliation was less than that of the bare GC electrode, whereas it was 3.8-fold higher for GCN coated from 120 min of exfoliation. The electrocatalytic activity of the GC electrodes modified with GCN was then tested by studying ascorbic acid (AA) and dopamine (DA) oxidation and reduction of hydrogen peroxide (HP). Among the different exfoliation times, GCN modified from 120 min of exfoliation displayed the highest electrocatalytic activity toward AA, DA, and HP. This was attributed to its higher EASA and lower charge-transfer resistance.

Carbon nanospheres modified with WO2-NaxWO3 nanoparticles for highly sensitive electrochemical detection of dopamine

WO2-NaxWO3 nanoparticles modified carbon spheres (WO2-NaxWO3/CSs) composite has been successfully synthesized by simple hydrothermal synthesis and high temperature calcination, and highly selective detection of dopamine (DA) was performed. The existence of WO2-NaxWO3 was confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectrum. Meanwhile, it can be seen from transmission electron microscopy (TEM) images that WO2-NaxWO3 was modified on the surface of carbon spheres in the form of nanometer-scaled particles. Cyclic voltammetry (CV) showed that the glassy carbon electrode modified by WO2-NaxWO3/CSs composite had strong electrocatalytic activity for DA oxidation, and a non-enzyme DA electrochemical sensor based on this material was constructed. Under the best conditions, the differential pulse voltammetry (DPV) signals of proposed sensor linearly increased with the increase of DA concentration in the range of 0.004 ~ 15.4 μM and 15.4 ~ 106.4 μM, with high sensitivity of 19.335 μA·μM−1·cm−2 and 3.151 μA·μM−1·cm−2, respectively, and a low limit of detection (LOD) of 1.3 nM (S/N = 3) and a limit of quantification (LOQ) of 4.3 nM were obtained. Furthermore, the sensor had good selectivity and satisfactory reproducibility and good stability for DA detection (RSD = 2.50%). It was successfully used to detect DA in animal serums, its recovery rate was between 1.10% and 2.91%, showing potential practical application value.

On the learning of addictive behavior: Sensation-seeking propensity predicts dopamine turnover in dorsal striatum

We asked if sensation-seeking is linked to premorbid personality characteristics in patients with addictive disorders, or the characteristics follow the sensation-seeking activity. We interpreted the former as a state associated with normal rates of dopamine synthesis, and the latter as a trait of individuals with abnormally high rates of synthesis. We previously determined dopaminergic receptor density in striatum, and we now tested the hypothesis that an elevated dopaminergic condition with increased extracellular dopamine and receptor density follows increased dopamine synthesis capacity in highly sensation-seeking individuals, as measured by positron emission tomography of 18 men with tracer fluorodopa (FDOPA). We detected a site in left caudate nucleus where the volume of distribution of FDOPA-derived metabolites correlated negatively with FDOPA metabolite turnover, consistent with decreased metabolite breakdown in highly sensation-seeking subjects. High rates of sensation-seeking attenuated the dopamine turnover in association with a low rate of dopamine recycling, low dopamine oxidation, and elevated extracellular dopamine and receptors in caudate nucleus. In contrast, low rates of sensation-seeking were associated with rapid dopamine recycling, rapid dopamine oxidation, low extracellular dopamine, and low receptor density. We conclude that the modulation of dopaminergic neurotransmission associated with sensation-seeking is a state of sensation-seeking, rather than a trait of personality following abnormal regulation of dopaminergic neurotransmission.

Stretchable and Bioadhesive Gelatin Methacryloyl-Based Hydrogels Enabled by in Situ Dopamine Polymerization.

Hydrogel patches with high toughness, stretchability, and adhesive properties are critical to healthcare applications including wound dressings and wearable devices. Gelatin methacryloyl (GelMA) provides a highly biocompatible and accessible hydrogel platform. However, low tissue adhesion and poor mechanical properties of cross-linked GelMA patches (i.e., brittleness and low stretchability) have been major obstacles to their application for sealing and repair of wounds. Here, we show that adding dopamine (DA) moieties in larger quantities than those of conjugated counterparts to the GelMA prepolymer solution followed by alkaline DA oxidation could result in robust mechanical and adhesive properties in GelMA-based hydrogels. In this way, cross-linked patches with ∼140% stretchability and ∼19 000 J/m3 toughness, which correspond to ∼5.7 and ∼3.3× improvement, respectively, compared to that of GelMA controls, were obtained. The DA oxidization in the prepolymer solution was found to play an important role in activating adhesive properties of cross-linked GelMA patches (∼4.0 and ∼6.9× increase in adhesion force under tensile and shear modes, respectively) due to the presence of reactive oxidized quinone species. We further conducted a parametric study on the factors such as UV light parameters, the photoinitiator type (i.e., lithium phenyl-2,4,6-trimethylbenzoylphosphinate, LAP, versus 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, Irgacure 2959), and alkaline DA oxidation to tune the cross-linking density and thereby hydrogel compliance for better adhesive properties. The superior adhesion performance of the resulting hydrogel along with in vitro cytocompatibility demonstrated its potential for use in skin-attachable substrates.

β-Amyloid fibrils catalyze neurotransmitter degradation

Amyloid fibrils are one of the hallmarks of Alzheimer's disease (AD), although a causative link between plaque-forming amyloid fibrils and AD pathology remains to be clarified. This study demonstrates, for the first time for a naturally occurring amyloid, that fibrils comprising the 42-residue amyloid-β peptide (Aβ42) exhibit significant catalytic properties. Aβ42 fibrils catalyzed the hydrolysis of the model ester para-nitrophenyl acetate (pNPA) and of acetylthiocholine, a surrogate for the neurotransmitter acetylcholine. Aβ42 fibrils also catalyzed oxidation of the prominent neurotransmitters dopamine and adrenaline. Importantly, the catalytic activity was specifically manifested by mature Aβ42 fibrils and not the peptide monomers or oligomeric Aβ42, the putative neurotoxic species. Furthermore, maximal catalytic activity was recorded by the full-length Aβ42 fibrils, whereas fibrillar assemblies comprising Aβ42 subdomains were significantly less catalytic. The catalytic activity of Aβ fibrils could exhibit insidious roles in AD pathophysiology.

Exploring a molecular switch for dopamine oxidation induced by charge reversal using scanning electrochemical microscopy

Oxidation of dopamine inside synaptic vesicles has been considered as one of inducements for Parkinson's disease. Dopamine molecules are often oxidized to quinones, making damages to neurotransmission process. Thus, exploring a controllable molecular switch for dopamine oxidation would make great significance in physiology. In this work, a binary homocysteine-dodecanethiol self-assembled monolayers was constructed on gold surface as a specific molecular switch. Scanning electrochemical microscopy was adopted to investigate the switch behavior for dopamine oxidation. The results showed that the molecular switch was at the ON state in a weak alkaline solution and dopamine oxidation would occur. While, the molecular switch was at the OFF state in a weak acidic solution and dopamine oxidation would be cut off. This controllable ON-OFF phenomenon was attributed to charge reversal on the surface of self-assembled monolayer. Then, Density Functional Theory calculation was adopted to calculate the HOMO-LUMO band gap of dopamine-homocysteine cluster. The theoretical calculation exhibited that charge reversal of homocysteine could adjust the energy barrier of dopamine oxidation. This work would offer some contributions to studies of dopamine oxidation in cellular physiology.

A novel graphene quantum dots/choline chloride/gold nanoparticles-modified carbon fiber microelectrode for sensitive and selective determination of dopamine in the presence of a high concentration of ascorbic acid

We prepared a three-layer composite of gold nanoparticles (AuNPs), choline (Ch) and graphene quantum dots (GQDs), and applied it to modify a carbon fiber microelectrode (CFME) by potentiostatic deposition to obtain a GQDs/Ch/AuNPs/CFME for high-sensitivity determination of dopamine (DA) without inference from ascorbic acid (AA). The surface morphology of electrodes was investigated by scanning electron microscopy. The electrochemical behavior of DA and AA at different modified electrodes was investigated by cyclic voltammetry and differential pulse voltammetry in Tris-HCl buffer (pH = 9.0). Owing to a synergistic effect, the GQDs/Ch/AuNPs/CFME exhibited an obvious electrocatalytic effect on positively charged DA and a significant shielding effect on negatively charged AA. The influence of experimental variables (duration of modification, pH of the working solution, scan rate) was studied. Under optimum conditions, in the presence of AA (1.0 × 10−3 mol/L), the GQDs/Ch/AuNPs/CFME described a fine linear enhancement for DA oxidation in the concentration range 0.01–10.0 μM with an estimated lower limit of detection of 1.616 nM and limit of quantification of 5.389 nM. The modified electrochemical sensor was applied for DA determination in the presence of high concentration of AA in mouse serum without separation steps and with good recovery.

Fabrication of bulk, nanosheets and quantum dots of graphitic carbon nitride on electrodes: Morphology dependent electrocatalytic activity

The present work aims to find a suitable morphology of graphitic carbon nitride (g-CN) for electrocatalytic applications which includes bulk g-CN (g-CNB), g-CN nanosheets (g-CNNS) and g-CN quantum dots (g-CND). The different morphologies of g-CN were synthesized by solid-phase thermal method using urea, citric acid and trisodium citrate as precursors. The X-ray diffraction (XRD) pattern of g-CNs showed characteristic 2θ values due to (0 0 2) interlayer diffraction and (1 0 0) in-plane structural packing. The g-CN with the morphology of bulk, sheets and dots were then attached directly on GC electrode by immersing it into the respective g-CN solution. The scanning electron microscopy (SEM) images showed that the g-CNB coated on GC plate displays layer like structure whereas g-CNNS exhibits crumpled and enfolded thin sheets like graphene. The SEM image of g-CND coated GC plate shows that they were uniformly covered the whole area as dots with the size of 30 nm. Under optimized conditions, the electrochemical impedance studies showed that the order of the charge transfer resistance was as follows: g-CNNS < g-CND < g-CNB < GC. The impact of g-CN morphology on the oxidation of ascorbic acid (AA) and dopamine (DA) and the reduction of hydrogen peroxide (HP) was studied at pH 7.2 phosphate buffer (PB) solution. The g-CNs modified electrodes irrespective of the morphology enhanced the electrocatalytic activity in contrast to bare GC electrode. Among the three g-CNs, GC/g-CNNS electrode exhibited higher electrocatalytic activity towards all the three analytes. The cause for the higher electrocatalytic activity was attributed to its higher electroactive surface area and faster electron transfer rate in contrast to GC/g-CNB and GC/g-CND electrodes. Further, GC/g-CNNS electrode was effectively used for the sensitive determination of HP. While increasing its concentration from 100 nM to 1 mM, HP reduction current increases linearly with R2 value of 0.9905 and LOD was 11 nM (S/N = 3). Finally, GC/g-CNNS electrode was successfully used to quantify HP in blood serum samples.

A simple and efficient voltammetric sensor for dopamine determination based on ZnO nanorods/electro-reduced graphene oxide composite

A nanocomposite of ZnO nanorods and electro-reduced graphene oxide (ZnONRs/ERGO) was prepared as cost-effective and efficient electrocatalyst for voltammetric detection of dopamine via a facile hydrothermal treatment followed by an electrochemical reduction. The ZnONRs were uniformly supported on the surface of conductive ERGO nanosheets, which enlarged the electroactive surface area and lowered the electron transfer resistant significantly. As a result, ZnONRs/ERGO modified glass carbon electrode (ZnONRs/ERGO/GCE) showed much more remarkable electrocatalytic activity toward dopamine oxidation than the controlled electrodes, with amplified response current and decreased over-potential. The extraordinary electrocatalytic activity is mainly attributed to the synergistic catalytic effects from ZnONRs and ERGO nanosheets. Using second derivative linear voltammetry (SDLSV), two wide dynamic response ranges (0.01 to 6.0 μM and 6.0 to 80 μM) were achieved at the ZnONRs/ERGO/GCE with an extremely low limit of detection (LOD) of 3.6 nM. The ZnONRs/ERGO/GCE also demonstrates excellent anti-interference ability and good repeatability, reproducibility as well as stability. Moreover, the ZnONRs/ERGO/GCE realized the accurate detection of dopamine concentration in human serum with good recoveries. Considering the outstanding advantages including low cost, simple manufacture, high efficiency, and superior sensing properties, ZnONRs/ERGO shows tremendous application prospects on real detection of catecholamine neurotransmitters.

An antifouling impedimetric sensor based on zinc oxide embedded polyvinyl alcohol nanoplatelets for wide range dopamine determination in the presence of high concentration ascorbic acid

Dopamine determination is of great importance for the early diagnosis of neurological diseases. However, dopamine sensors mostly encounter important challenges such as surface fouling and interference of co-existing biochemicals. Here, nanoplatelets of zinc oxide embedded polyvinyl alcohol (NP-ZnO/PVA) were utilized for providing an efficient fouling-free surface for selective dopamine determination in concentrations as high as 3 mM of dopamine in the presence of ascorbic acid interference. The fouling-free properties was provided mainly by pH-inducibility of the NP-ZnO/PVA nanocomposite at the rationally adjusted sensing conditions. ZnO plays a vital role in the electrocatalytic oxidation of dopamine, and PVA provides surface functional groups that minimize the surface interactions with interferences or fouling agents. The NP-ZnO/PVA nanocomposite fabrication process was performed by PVA assisted ZnO electro-synthesis onto the surface of fluorine-doped tin oxide (FTO) conducting glass. The fabricated FTO/NP-ZnO/PVA sensor was characterized utilizing FE-SEM, EDX, XRD, TGA-DTG, BET-BJH and FTIR techniques. Impedimetric determination of dopamine was performed in the wide linear range from 20.0 nM to 3.0 mM with a low detection limit of 5.0 nM. The applicability of FTO/NP-ZnO/PVA for dopamine determination was successfully tested in real samples. The NP-ZnO/PVA provides a great prospective to be an efficacious material for the construction of dopamine electrochemical sensing platforms.

Aptamer-Modified Cu2+-Functionalized C-Dots: Versatile Means to Improve Nanozyme Activities-"Aptananozymes".

The covalent linkage of aptamer binding sites to nanoparticle nanozymes is introduced as a versatile method to improve the catalytic activity of nanozymes by concentrating the reaction substrates at the catalytic nanozyme core, thereby emulating the binding and catalytic active-site functions of native enzymes. The concept is exemplified with the synthesis of Cu2+ ion-functionalized carbon dots (C-dots), modified with the dopamine binding aptamer (DBA) or the tyrosinamide binding aptamer (TBA), for the catalyzed oxidation of dopamine to aminochrome by H2O2 or the oxygenation of l-tyrosinamide to the catechol product, which is subsequently oxidized to amidodopachrome, in the presence of H2O2/ascorbate mixture. Sets of structurally functionalized DBA-modified Cu2+ ion-functionalized C-dots or sets of structurally functionalized TBA-modified Cu2+ ion-functionalized C-dots are introduced as nanozymes of superior catalytic activities (aptananozymes) toward the oxidation of dopamine or the oxygenation of l-tyrosinamide, respectively. The aptananozymes reveal enhanced catalytic activities as compared to the separated catalyst and respective aptamer constituents. The catalytic functions of the aptananozymes are controlled by the structure of the aptamer units linked to the Cu2+ ion-functionalized C-dots. In addition, the aptananozyme shows chiroselective catalytic functions demonstrated by the chiroselective-catalyzed oxidation of l/d-DOPA to l/d-dopachrome. Binding studies of the substrates to the different aptananozymes and mechanistic studies associated with the catalytic transformations are discussed.

Pico Molar Sensing of Dopamine in Presence of Serotonin Using BaMnO3/Carbon Nanostructures

A novel electrochemical sensor for dopamine (DA) in the presence of serotonin (ST) was fabricated by modifying a glassy carbon electrode with BaMnO3 and super P carbon black. The modifier, BaMnO3 was synthesized by a co-precipitation method and subsequent calcination. The formation of a pure crystalline form of BaMnO3 was ensured during synthesis and verified by characterization techniques such as powder X-ray diffraction, infrared spectroscopy, Raman, thermogravimetry, Ultraviolet–visible spectroscopy, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray analysis. 5 mg of BaMnO3 was sufficient to allow sensor development. The sensor was characterized by electrochemical impedance spectra and cyclic voltammetry studies. The mechanism of oxidation of DA and ST at the sensor is proposed based on experimental findings. Trace level determination of DA and ST was successfully carried out using the sensor. The electrochemical oxidation of DA and ST are completely independent. The limit of detection of DA and ST are 50 pM and 5 nM respectively. The DA has a linear dynamic range (LDR) of 0.1 to 300 nM and ST has a LDR of 10 to 2300 nM. The practical utility of the sensor was demonstrated by calculating the recovery of DA in human blood serum and urine.

Nanotube‐Boramidic Acid Derivative for Dopamine Sensing

AbstractA new sensor, based on boramidic acid‐bounded MWCNTs (Multi‐walled carbon nanotubes), was synthesized in three simple steps. Modification of the sensor surface was accomplished using boric acid in which the boron atom is adjacent to the NH group. Characterization, electrochemical behaviors, and stability of newly modified nanosensor were completed using SEM (scanning electron microscope), TEM (Transmission electron microscope), CV (cyclic voltammetry), EIS (electron impedance), DTA (Differential thermal analysis), and XPS (X‐ray photoelectron spectroscopy). SEM and TEM analysis were confirmed the modified surface of the nanosensor. The stability of the newly synthesized sensor was also designated that the initial weight loss occurred between 50–145 °C was corresponded to the degradation of both ethylene diamine and boric acid. According to the EIS study, the Nyquist plot of the MWCNTs‐NH‐B (OH)2/GC electrode displayed a 0.435 kΩ Rct with a smaller semicircle than the bare GC (6.57 kΩ). The electrochemical behavior of dopamine was investigated using cyclic and square wave voltammetry (0.1 M phosphate buffer solution‐pH 7.4). The diffusion‐controlled process was determined when the oxidation of dopamine was studied. The detection limit of dopamine was found to be 5.1 nM. An actual sample study was done using the developed analytical method, and the detection of dopamine in urine was successfully performed. This study is the first example of boramidic acid‐modified multi‐walled carbon nanotubes

Adsorption of aflatoxins and ochratoxins in edible vegetable oils with dopamine-coated magnetic multi-walled carbon nanotubes

A new, green, and cost-effective magnetic solid-phase extraction of aflatoxins and ochratoxins from edible vegetable oils samples was developed using polydopamine-coated magnetic multi-walled carbon nanotubes (PDA@Fe3O4-MWCNTs) as the absorbent. PDA@Fe3O4-MWCNTs nanomaterials were prepared by chemical co-precipitation and in situ oxidation and self-polymerization of dopamine and was characterized. Factors affecting MSPE and the adsorption behavior of the adsorbent to mycotoxins were studied, and the optimal extraction conditions of MSPE and the complexity of the adsorption process were determined. Based on this, the magnetic solid-phase extraction-high-performance liquid chromatography-fluorescence detection method (MSPE-HPLC-FLD) was established for determining six mycotoxins [aflatoxin B1 (AFB1), AFB2, AFG1, and AFG2, and ochratoxin A (OTA) and OTB)] in vegetable oils. The recovery was 70.15%~89.25%, and RSD was ≤6.4%. PDA@Fe3O4-MWCNTs showed a high affinity toward aflatoxins and ochratoxins, allowing selective extraction and quantification of aflatoxins and ochratoxins from complex sample matrices.

Perylene diimide/MXene-modified graphitic pencil electrode-based electrochemical sensor for dopamine detection.

The synthesis of novel architecture comprising perylene diimide (PDI)-MXene (Ti3C2TX)-integrated graphitic pencil electrode for electrochemical detection of dopamine (DA)is reported. The good electron passage between PDI-MXene resulted in an unprecedented nano-adduct bearing enhanced electrocatalytic activity with low-energy electronic transitions. The anionic groups of PDI corroborated enhanced active surface area for selective binding and robust oxidation of DA, thereby decreasing the applied potential. Meanwhile, the MXene layers acted as functional conducive support for PDI absorption via strong H-bonding. The considerable conductivity of MXene enhanced electron transportation thus increasing the sensitivity of sensing interface. Theinclusively engineered nano-adduct resulted in robust DA oxidation with ultra-sensitivity (38.1 μAμM-1cm-2), andlow detection limit (240 nM) at very low oxidation potential (-0.135 V). Moreover, it selectively signaled DA in the presence of physiological interferents with wide linearity (100-1000 μM). The developed transducing interface performed well in human serum samples with RSD (0.1 to 0.4%) and recovery (98.6 to 100.2%) corroborating the viability of the practical implementation of this integrated system. Graphical abstract Schematic illustration of the oxidative process involved on constructed sensing interface for the development of a non-enzymatic dopamine sensor.

Construction of a highly sensitive signal electrochemical sensor based on self-assembled cobalt oxide-hydroxylated single-walled carbon nanotubes composite for detection of dopamine in bovine serum samples

A novel electrochemical sensor based cobalt oxide nanoparticles and hydroxylated single-walled carbon nanotubes composite (Co3O4/SWCNTs-OH) for the highly sensitive detection of dopamine (DA) was successfully developed in present work. Spinel Co3O4 crystals were synthesized by a facile hydrothermal process without high-temperature calcination procedure, and then self-assembled with SWCNTs-OH. The obtained Co3O4/SWCNTs-OH composite possesses large surface area and cross-linked structure. The morphology, compositions, surface functional groups, and crystal structure of Co3O4/SWCNTs-OH composite were characterized by Field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The electrochemical properties and catalytic performance of prepared sensor (Co3O4/SWCNTs-OH/GCE) were studied by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). These results showed that Co3O4/SWCNTs-OH/GCE exhibited excellent electrocatalytic performance in terms of DA oxidation peak potential and current density in comparison with bare GCE, Co3O4/GCE and SWCNTs-OH/GCE. Under optimum conditions, Co3O4/SWCNTs-OH/GCE exhibited a good linear relationship between DA concentrations and current responses in the range 1–100 μM. Low detection limit of 0.08 μM (signal-to-noise ratio of 3, S/N = 3) and high sensitivity of 1.427 μA μM−1 could be observed at Co3O4/SWCNTs-OH/GCE. In addition, the quantitative detection of DA in bovine serum samples at Co3O4/SWCNTs-OH/GCE showed satisfactory recoveries (93.68–105.47%) and low relative standard deviation (RSD) (3.02–5.83%). The outstanding sensitivity, good selectivity and reproducibility of Co3O4/SWCNTs-OH/GCE might be attributed to the synergistic effects between Co3O4 and SWCNTs-OH. The fabricated Co3O4/SWCNTs-OH composite might be used as a promising catalyst for the practical electrochemical detection of DA.

Polyoxometalate-based catenane as sensing material for electrochemical detection of dopamine

Polyoxometalate-based crystalline materials as electro-active medium have exhibited excellent performances as bio/chemical sensors, particularly when synergy is reached upon combining with conductive materials. In this study, a catenane Keggin-type phosphomolybdic acid-based Ag-triazole framework and reduced graphene oxide (PMo12[6]catenane/rGO) was synthesized and employed to fabricate a modified electrode to detect the neurotransmitter dopamine (DA). Results show that PMo12[6]catenane and rGO composite modified electrode had strong catalytic activity for oxidation of DA and exhibited wide linear detection range from 1 to 90 μM with the limit of detection (LOD) of 0.890 μM and 1–44 μM with LOD 0.065 μM (S/N = 3). No interference from uric acid (UA) and ascorbic acid (AA) demonstrates that PMo12[6]catenane and rGO composite modified electrode possesses good selectivity to DA detection. The work can promote the further development of POMOFs with different structures in sensing applications.