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1.
Talanta ; 231: 122334, 2021 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-33965015

RESUMO

A composite fluorescent nanoprobe based on metal enhanced fluorescence (MEF) effect of gelatin-coated silver nanoparticles (AgNPs@gel) was developed for selective and sensitive detection of dopamine (DA). The characteristic fluorescence of Tb(III) was using as the detection signal and AgNPs@gel served as substrates of the MEF. Gelatin with rich amine and carboxylic groups was used not only as a co-ligand of Tb(III) complex, but also as a bridging substance and a spacing material for improving the MEF of AgNPs@gel on the intrinsic luminescent intensity of Tb(III). Under the optimal conditions, the increment of the fluorescence intensity (measured at 307/544 nm as excitation/emission wavelength) of the system increased linearly with the concentration of DA in the range of 0.80-100 nM (R2 = 0.9937) and 100-1000 nM (R2 = 0.9978). The fluorescent probe greatly improved Tb(III) luminescence, which paved the way for sensitive detection with a low detection limit of 0.54 nM. It also showed good selectivity among other neurotransmitters. This work was successfully applied to the determination of DA in human serum samples with recoveries ranging from 99.8 to 102.2%. We believe that the Tb(III)-DA-AgNPs@gel composite fluorescent probe can be developed as a new approach for DA detection.


Assuntos
Dopamina/análise , Nanopartículas Metálicas , Prata , Térbio , Fluorescência , Gelatina , Humanos , Limite de Detecção , Espectrometria de Fluorescência
2.
Inorg Chem ; 60(3): 1893-1901, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33439641

RESUMO

Herein, a new series of magnetic Fe-doped CoO nanocomposites (Fe-CoO NCs) with dual enzyme-like activities (peroxidase and oxidase) were successfully synthesized. The molar ratio of Fe3+/Co2+ salts during the solvothermal process determined the morphology and catalytic activity of the NCs. Among them, the flower-like 0.15Fe-CoO NCs showed high peroxidase-mimicking activity over a wider pH range of 4-5 and a temperature range of 30-50 °C. Such nanozymes were applied for constructing a facile and sensitive colorimetric sensor to detect H2O2 and dopamine (DA) in the linear ranges of 6-20 and 2-10 µM with limits of detection (LODs) of 4.40 and 1.99 µM, respectively. The excellent magnetic separation performance and successful DA detection in human urine samples validated the promising application of CoO-based nanozymes in medical diagnosis. The superior catalytic behaviors of 0.15Fe-CoO NCs could be ascribed to the high surface area, open mesoporous structure, increased surface active species, and the facile redox of Fe3+/Fe2+ and Co3+/Co2+. Based on the results of the fluorescent probe and radical trapping tests, the possible mechanism that Fe doping promoted the decomposition of H2O2 to produce hydroxyl radical (•OH) and superoxide radical (•O2-) was proposed.


Assuntos
Cobalto/química , Dopamina/análise , Peróxido de Hidrogênio/análise , Ferro/química , Nanocompostos/química , Óxidos/química , Colorimetria , Fenômenos Magnéticos , Tamanho da Partícula , Propriedades de Superfície
3.
J Colloid Interface Sci ; 582(Pt B): 732-740, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-32916573

RESUMO

A novel nanosensor with peroxidase enzyme-mimetic activity, based on CuS-BSA-Cu3(PO4)2 nanoparticles, was developed. CuS-BSA nanoparticles were first synthesized using a facile bio-mineralization assay. Conjugation of Cu3(PO4)2 with CuS-BSA generates CuS-BSA-Cu3(PO4)2 nanoparticles (NPs) of 10 nm in size with high catalytic activity against a peroxidase substrate, 3,3',5,5'-tetramethylbenzidine (TMB). The catalytic action was based on a remarkable color change from colorless TMB into blue oxidized product (oxTMB) with absorption maximum at 654 nm. The enzyme-mimetic activity of CuS-BSA-Cu3(PO4)2 nanoparticles was believed to occur through hydroxyl radical (HO) generation in presence of H2O2, which was inhibited upon addition of dopamine. Increasing concentrations of dopamine induced a gradual decrease of the nanoparticles' catalytic activity. The developed colorimetric sensor displayed a limit of detection of 0.13 µM for dopamine over 0.05-100 µM linear range and high specificity. The performance of the nanosensor for sensing dopamine in beef meat and blood samples was evaluated and proved to be promising for diagnostic applications without the requirement of complex and expensive instrumentation.


Assuntos
Cobre , Nanopartículas , Animais , Bovinos , Colorimetria , Dopamina/análise , Peróxido de Hidrogênio , Carne , Fosfatos , Soroalbumina Bovina , Sulfetos
4.
Bioelectrochemistry ; 137: 107646, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32957020

RESUMO

Chemically inert and biocompatible boron-doped diamond (BDD) has been successfully used in neuroscience for sensitive neurochemicals sensing and/or as a growth substrate for neurons. In this study, several types of BDD differing in (i) fabrication route, i.e. conventional microwave plasma enhanced chemical vapour deposition (MW-PECVD) reactor vs. MW-PECVD with linear antenna delivery system, (ii) morphology, i.e. planar vs. porous BDD, and (iii) surface treatment, i.e. H-terminated (H-BDDs) vs. O-terminated (O-BDDs), were characterized from a morphological, structural, and electrochemical point of view. Further, planar and porous BDD-based electrodes were tested for sensing of dopamine in common biomimicking environments of pH 7.4, namely phosphate buffer (PB) and HEPES buffered saline (HBS). In HBS, potential windows are narrowed due to electrooxidation of its buffering component (i.e. HEPES), however, dopamine sensing in HBS is possible. H-BDDs (both planar and porous) outperformed O-BDDs as they provided clearer dopamine signals with higher peak currents. As expected, due to its enlarged surface area and increased sp2 content, the highest sensitivity and lowest detection limits of 8 × 10-8 mol L-1 and 6 × 10-8 mol L-1 in PB and HBS media, respectively, were achieved by square-wave voltammetry on porous H-BDD.


Assuntos
Boro/química , Meios de Cultura/química , Diamante/química , Dopamina/análise , Técnicas Eletroquímicas/métodos , Eletrodos , Biomimética , Limite de Detecção , Microscopia Eletrônica de Varredura , Reprodutibilidade dos Testes , Análise Espectral Raman/métodos
5.
Food Chem ; 335: 127646, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-32731123

RESUMO

Carbon/ZnO coaxial microfibers were synthesized with the hypha of Penicillium expansum as low-cost and green template. The SEM images, XRD and Raman spectra were used to characterize the morphology and chemical components of the prepared microfibers. The formation of the coaxial structure could be attributed to the attachment of Zn2+ onto the hypha surface through coordination and electrostatic interactions. Sensing performance of the carbon/ZnO microfibers toward Dopamine (DA) were evaluated by dropping method. Results showed that the proposed sensor exhibited good selectivity, reproducibility, and stability with a detection limit of 0.106 µM. Two linear ranges were obtained from 0 to 50 and 50 to 300 µM. The practicality of the carbon/ZnO microfibers was supported by the successful detection of DA in pork with recovery ranging from 96.85% to 104.51%. Based on the excellent electrochemical performance and easy preparation, the proposed sensor provides a promising method for determination of DA.


Assuntos
Técnicas Biossensoriais/métodos , Carbono/química , Carbono/metabolismo , Dopamina/análise , Hifas/metabolismo , Carne/análise , Penicillium/metabolismo , Óxido de Zinco/química , Óxido de Zinco/metabolismo , Animais , Técnicas Biossensoriais/instrumentação , Hifas/crescimento & desenvolvimento , Penicillium/crescimento & desenvolvimento , Suínos
6.
Gen Physiol Biophys ; 39(4): 393-398, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32902408

RESUMO

It is known that early-life stress events induce profound consequences on emotional brain regions including amygdala, involved in emotional processing and the ventral tegmental area (VTA), which contains neuron cell bodies of the mesolimbic dopaminergic system. The aim of this study is to test the hypothesis that stress induced by long-term social isolation from weaning in female rats is associated with alterations in amygdalar dopamine receptor gene expression and VTA dopamine concentrations. Rats were weaned on postnatal day 21 and then exposed to stress of chronic isolation for 9 weeks. Control animals were housed socially. Amygdalar dopamine D1 but not D2 receptor gene expression was decreased in isolated rats compared to controls. Dopamine concentrations in the VTA were enhanced following chronic isolation. A negative correlation was observed between amygdalar D1 gene expression and dopamine concentrations in the VTA. In conclusion, a reduction of dopamine D1 receptor gene expression in the amygdala in response to stress induced by chronic isolation in female rats was accompanied by an increase in dopamine concentration in the VTA. Further studies are needed to understand the physiological significance, if any, of negative association of amygdalar dopamine receptor D1 gene expression and dopamine concentrations in the VTA.


Assuntos
Dopamina/análise , Receptores de Dopamina D2 , Isolamento Social , Estresse Psicológico , Área Tegmentar Ventral , Desmame , Animais , Emoções , Feminino , Ratos , Receptores de Dopamina D2/genética , Receptores de Dopamina D2/metabolismo , Área Tegmentar Ventral/metabolismo
7.
J Chromatogr A ; 1627: 461403, 2020 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-32823108

RESUMO

Dopamine is a catecholamine neurotransmitter that degrades rapidly in aqueous solutions; hence, its analysis following brain microdialysis is challenging. The aim of the current study was to develop and validate a new microdialysis coupled LC-MS/MS system with improved accuracy, precision, simplicity and turnaround time for dopamine, serotonin, methamphetamine, amphetamine, 4-hydroxymethamphetamine and 4-hydroxyamphetamine analysis in the brain. Dopamine degradation was studied with different stabilizing agents under different storage conditions. The modified microdialysis system was tested in vitro, and was optimized for best probe recovery, assessed by %gain. LC-MS/MS assay was developed and validated for the targeted compounds. Stabilizing agents (ascorbic acid, EDTA and acetic acid) as well as internal and cold standards were added on-line to the dialysate flow. Assay linearity range was 0.01-100 ng/mL, precision and accuracy passed criteria, and LOQ and LLOQ were 0.2 and 1.0 pg, respectively. The new microdialysis coupled LC-MS/MS system was used in Wistar rats striatum after 4 mg/kg subcutaneous methamphetamine. Methamphetamine rapidly distributed to rat striatum reaching an average ~200 ng/mL maximum, ~82.5 min post-dose. Amphetamine, followed by 4-hydroxymethamphetamine, was the most abundant metabolite. Dopamine was released following methamphetamine injection, while serotonin was not altered. In conclusion, we proposed and tested an innovative and simplified solution to improve stability, accuracy and turnover time to monitor unstable molecules, such as dopamine, by microdialysis.


Assuntos
Encéfalo/metabolismo , Dopamina/análise , Metanfetamina/análise , Serotonina/análise , Espectrometria de Massas em Tandem/métodos , Animais , Cromatografia Líquida de Alta Pressão , Dopamina/isolamento & purificação , Dopamina/metabolismo , Meia-Vida , Masculino , Metanfetamina/isolamento & purificação , Metanfetamina/metabolismo , Microdiálise , Ratos , Ratos Wistar , Serotonina/isolamento & purificação , Serotonina/metabolismo
8.
Yakugaku Zasshi ; 140(8): 979-983, 2020.
Artigo em Japonês | MEDLINE | ID: mdl-32741871

RESUMO

Monoamine neurotransmitters are released by specialized neurons that regulate behavioral and cognitive functions. Although localization of monoaminergic neurons in the brain is well known, the distribution, concentration, and kinetics of monoamines remain unclear. We used mass spectrometry imaging (MSI) for simultaneous and quantitative imaging of endogenous monoamines to generate a murine brain atlas of serotonin (5-HT), dopamine (DA), and norepinephrine (NE) levels. We observed several nuclei rich in both 5-HT and a catecholamine (DA or NE). Additionally, we analyzed de novo monoamine synthesis or fluctuations in those nuclei. We propose that MSI is a useful tool to gain deeper understanding of associations among the localization, levels, and turnover of monoamines in different brain areas and their role in inducing behavioral changes.


Assuntos
Monoaminas Biogênicas/análise , Monoaminas Biogênicas/metabolismo , Mapeamento Encefálico/métodos , Encéfalo/metabolismo , Espectrometria de Massas/métodos , Imagem Molecular/métodos , Neurotransmissores/metabolismo , Animais , Dopamina/análise , Dopamina/metabolismo , Camundongos , Neurônios/metabolismo , Neurotransmissores/fisiologia , Norepinefrina/análise , Norepinefrina/metabolismo , Serotonina/análise , Serotonina/metabolismo
9.
Ecotoxicol Environ Saf ; 201: 110872, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32559693

RESUMO

Based on a hybrid carbon nanotube composite, a novel electrochemical sensor with high sensitivity and selectivity was designed for the simultaneous determination of dopamine (DA) and uric acid (UA). The hybrid carbon nanotube composite was prepared by ultrasonic assembly of carboxylated multi-walled carbon nanotube (MWCNT-COOH) and hydroxylated single-walled carbon nanotube (SWCNT-OH). And the hybrid (MWCNT-COOH/SWCNT-OH) composite was characterized by field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared (FT-IR) spectroscopy. The electrochemical performances of MWCNT-COOH/SWCNT-OH composite modified glassy carbon electrode (MWCNT-COOH/SWCNT-OH/GCE) were analyzed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). Under the optimum experimental conditions, the as-prepared sensor showed high sensitivity and selectivity for DA and UA. The calibration curves obtained were linear for the currents versus DA and UA concentrations in the range 2-150 µM, and limits of detection (LODs) were calculated to be 0.37 µM and 0.61 µM (signal-to-noise ratio of 3, S/N = 3), respectively. The recoveries of DA and UA in bovine serum samples at MWCNT-COOH/SWCNT-OH/GCE were in the range 96.18-105.02%, and relative standard deviations (RSDs) were 3.34-7.27%. The proposed electrochemical sensor showed good anti-interference ability, excellent reproducibility and stability, as well as high selectivity, which might provide a promising platform for determination of DA and UA.


Assuntos
Dopamina/análise , Técnicas Eletroquímicas/métodos , Nanotubos de Carbono/química , Ácido Úrico/análise , Animais , Carbono , Bovinos , Dopamina/sangue , Eletrodos , Limite de Detecção , Nanotubos de Carbono/ultraestrutura , Reprodutibilidade dos Testes , Ácido Úrico/sangue
10.
Sci Rep ; 10(1): 3772, 2020 02 28.
Artigo em Inglês | MEDLINE | ID: mdl-32111933

RESUMO

In this study, ultrasensitive and precise detection of a representative brain hormone, dopamine (DA), was demonstrated using functional conducting polymer nanotubes modified with aptamers. A high-performance aptasensor was composed of interdigitated microelectrodes (IMEs), carboxylated polypyrrole nanotubes (CPNTs) and DA-specific aptamers. The biosensors were constructed by sequential conjugation of CPNTs and aptamer molecules on the IMEs, and the substrate was integrated into a liquid-ion gating system surrounded by pH 7.4 buffer as an electrolyte. To confirm DA exocytosis based on aptasensors, DA sensitivity and selectivity were monitored using liquid-ion gated field-effect transistors (FETs). The minimum detection level (MDL; 100 pM) of the aptasensors was determined, and their MDL was optimized by controlling the diameter of the CPNTs owing to their different capacities for aptamer introduction. The MDL of CPNT aptasensors is sufficient for discriminating between healthy and unhealthy individuals because the total DA concentration in the blood of normal person is generally determined to be ca. 0.5 to 6.2 ng/mL (3.9 to 40.5 nM) by high-performance liquid chromatography (HPLC) (this information was obtained from a guidebook "Evidence-Based Medicine 2018 SCL " which was published by Seoul Clinical Laboratory). The CPNTs with the smaller diameters (CPNT2: ca. 120 nm) showed 100 times higher sensitivity and selectivity than the wider CPNTs (CPNT1: ca. 200 nm). Moreover, the aptasensors based on CPNTs had excellent DA discrimination in the presence of various neurotransmitters. Based on the excellent sensing properties of these aptasensors, the DA levels of exogeneous DA samples that were prepared from PC12 cells by a DA release assay were successfully measured by DA kits, and the aptasensor sensing properties were compared to those of standard DA reagents. Finally, the real-time response values to the various exogeneous DA release levels were similar to those of a standard DA aptasensor. Therefore, CPNT-based aptasensors provide efficient and rapid DA screening for neuron-mediated genetic diseases such as Parkinson's disease.


Assuntos
Aptâmeros de Nucleotídeos/química , Técnicas Biossensoriais , Dopamina , Exocitose , Nanotubos/química , Animais , Dopamina/análise , Dopamina/metabolismo , Células PC12 , Pirróis/química , Ratos , Transistores Eletrônicos
11.
Biosensors (Basel) ; 10(3)2020 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-32204548

RESUMO

We demonstrate a facile methodology for the mass production of graphene oxide (GO) bulk-modified screen-printed electrodes (GO-SPEs) that are economical, highly reproducible and provide analytically useful outputs. Through fabricating GO-SPEs with varying percentage mass incorporations (2.5%, 5%, 7.5% and 10%) of GO, an electrocatalytic effect towards the chosen electroanalytical probes is observed, which increases with greater GO incorporated compared to bare/graphite SPEs. The optimum mass ratio of 10% GO to 90% carbon ink produces an electroanalytical signal towards dopamine (DA) and uric acid (UA) which is ca. ×10 greater in magnitude than that achievable at a bare/unmodified graphite SPE. Furthermore, 10% GO-SPEs exhibit a competitively low limit of detection (3σ) towards DA at ca. 81 nM, which is superior to that of a bare/unmodified graphite SPE at ca. 780 nM. The improved analytical response is attributed to the large number of oxygenated species inhabiting the edge and defect sites of the GO nanosheets, which are able to exhibit electrocatalytic responses towards inner-sphere electrochemical analytes. Our reported methodology is simple, scalable, and cost effective for the fabrication of GO-SPEs that display highly competitive LODs and are of significant interest for use in commercial and medicinal applications.


Assuntos
Dopamina/análise , Grafite/química , Ácido Úrico/análise , Técnicas Biossensoriais , Técnicas Eletroquímicas , Eletrodos , Desenho de Equipamento , Limite de Detecção
12.
Sensors (Basel) ; 20(4)2020 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-32075167

RESUMO

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.


Assuntos
Técnicas Biossensoriais , Dopamina/análise , Técnicas Eletroquímicas/métodos , Técnicas Eletroquímicas/tendências , Óptica e Fotônica , Humanos , Polímeros/química , Transmissão Sináptica
13.
Anal Chim Acta ; 1102: 46-52, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-32043995

RESUMO

The electrochemical flow cell containing track-etched microporous membrane electrodes was applied to a dual-electrode coulometric detector for microbore/capillary HPLC with a small injection volume and low eluent flow rate. The proposed flow cell with a 0.1-mm diameter inlet channel gave a detection volume of 0.08 nL per electrode, which was determined by the eluent flow through the electrode. For the dual-electrode detector, the calculated volume was 0.24 nL. The efficiency of electrooxidation of l-ascorbic acid increased as the flow rate decreased and was close to 100% when the flow rate was below 50 µL min-1, which is a common flow rate in microbore or capillary liquid chromatography. Catecholamines, such as noradrenaline, adrenaline, and dopamine, were detected by total conversion with two-electron oxidation in the potential range from 0.8 to 1.0 V vs. Ag/AgCl after separation with a microbore column. These peaks were accompanied by corresponding cathodic peaks derived from quasi-stable electrooxidation products of the catecholamines. The detection limits of noradrenaline, adrenaline, and dopamine were 0.1, 0.1, and 0.2 µM, respectively. The RSD values for five replicate measurements of 5.0 µM of these compounds were 0.9%, 0.7%, and 1.5%, respectively. Coulometric detection was also demonstrated by determination of catecholamines in pharmaceuticals.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Técnicas Eletroquímicas/métodos , Eletrodos , Membranas Artificiais , Ácido Ascórbico/química , Cromatografia Líquida de Alta Pressão/instrumentação , Dopamina/análise , Dopamina/química , Técnicas Eletroquímicas/instrumentação , Epinefrina/análise , Epinefrina/química , Limite de Detecção , Norepinefrina/análise , Norepinefrina/química , Oxirredução
14.
Mikrochim Acta ; 187(1): 94, 2020 01 04.
Artigo em Inglês | MEDLINE | ID: mdl-31902014

RESUMO

Poly(3,4-ethylenedioxythiophene) (PEDOT) films were electrodeposited by cyclic voltammetry on a glassy carbon electrode (GCE) in aqueous solution. Three kinds of supporting electrolytes were used, viz. graphene oxide (GO), phosphate buffered saline (PBS), and GO in PBS, respectively. The surface morphology of the modified electrodes was characterized by scanning electron microscopy. The electrochemical performance of the modified electrodes was investigated by cyclic voltammetry and electrochemical impedance spectroscopy by using the hexacyanoferrate redox system. The results demonstrate that the PEDOT-GO/GCE, which was electropolymerized in aqueous solutions containing EDOT and GO, shows the best electrochemical activities compared with other modified electrodes. The electrochemical behaviors of ascorbic acid (AA), dopamine (DA) and uric acid (UA) were investigated by cyclic voltammetry. The PEDOT-GO/GCE exhibits enhanced electrocatalytic activities towards these important biomolecules. Under physiological pH conditions and in the mixed system of AA, DA and UA, the modified GCE exhibits the following figures of merit: (a) a linear voltammetric response in the concentration ranges of 100-1000 µM for AA, 6.0-200 µM for DA, and 40-240 µM for UA; (b) well separated oxidation peaks near 31, 213 and 342 mV (vs. saturated Ag/AgCl) for AA, DA and UA, respectively; and (c) detection of limits (at S/N = 3) of 20, 2.0 and 10 µM. The results demonstrate that GO, based on its relatively large number of anionic sites, can be used as the sole weak electrolyte and charge balance dopant for the preparation of functionally doped conducting polymers by electrodeposition. Graphical abstractSchematic representation of a nanostructure composed of hybrid conducting polymer PEDOT-GO nanocomposites, and its application to simultaneous determination of ascorbic acid, dopamine and uric acid.


Assuntos
Ácido Ascórbico/análise , Dopamina/análise , Técnicas Eletroquímicas/métodos , Ácido Úrico/análise , Compostos Bicíclicos Heterocíclicos com Pontes , Técnicas Eletroquímicas/normas , Eletrodos , Galvanoplastia/métodos , Ferrocianetos/química , Grafite , Oxirredução , Polímeros
15.
Mikrochim Acta ; 187(1): 82, 2020 01 02.
Artigo em Inglês | MEDLINE | ID: mdl-31897862

RESUMO

An electrochemical sensor is described for the simultaneous voltammetric determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA). An indium-tin oxide (ITO) electrode was modified with a hierarchical core-shell metal-organic framework and Ag-doped mesoporous metal-oxide based hybrid nanocomposites on g-C3N4 nanosheets. The morphology, structural and chemical composition of the hybrid nanocomposite was characterized using different analytical methods. The modified ITO showed superior electrocatalytic performance towards the oxidation of AA, DA and UA due to the enhanced surface area, synergistic effects and well-organized porous assembly. Figures of merit, include (a) linear responses from 0.1 to 200 µM, 2.5 to 100 µM and 2.5 to 625 µM; (b) detection limits (at S/N = 3) of 0.02, 0.01 and 0.06 µM, and (c) well separated oxidation peaks near -50, 186 and 390 mV (vs. Ag/AgCl) for simultaneous sensing AA, DA and UA, respectively. The sensor was evaluated by analysing spiked serum samples and gave data with precision, with recoveries of >98%. Graphical abstractSchematic Representation of a Mesoporous Silver-doped TiO2-SnO2 Nanocomposite (h-ATS) on g-C3N4 Nanosheets and Decorated with a Hierarchical Core-Shell Metal-Organic Framework (NC@GC) Based Electrochemical Sensor for Simultaneous Voltammetric Detection of Ascorbic acid, Dopamine and Uric acid.


Assuntos
Ácido Ascórbico/análise , Dopamina/análise , Eletroquímica/métodos , Estruturas Metalorgânicas/química , Nanocompostos/química , Nanoestruturas/química , Ácido Úrico/análise , Ácido Ascórbico/sangue , Dopamina/sangue , Eletroquímica/normas , Eletrodos , Grafite/química , Compostos de Nitrogênio/química , Prata , Compostos de Estanho , Titânio , Ácido Úrico/sangue
16.
Analyst ; 145(5): 1768-1776, 2020 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-31915763

RESUMO

The development of a separation-based sensor for catecholamines based on microdialysis (MD) coupled to microchip electrophoresis (ME) with electrochemical (EC) detection is described. The device consists of a pyrolyzed photoresist film working electrode and a poly(dimethylsiloxane) microchip with a flow-gated sample injection interface. The chip was partially reversibly sealed to the glass substrate by selectively exposing only the top section of the chip to plasma. This partially reversible chip/electrode integration process not only allows the reuse of the working electrode but also greatly enhanced the reproducibility of electrode alignment with the separation channel. The developed MD-ME-EC system was then tested using l-DOPA, 3-O-MD, HVA, DOPAC, and dopamine standards, which were separated in less than 100 seconds using a background electrolyte consisting of 15 mM sodium phosphate (pH 7.4), 15 mM sodium dodecyl sulfate, and 2.5 mM boric acid. A potential of +1.0 V vs. Ag/AgCl was used for amperometric detection of the analytes. The device was evaluated for on-line monitoring of the conversion of l-DOPA to dopamine in vitro and for monitoring dopamine release in an anesthetized rat in vivo following high K+ stimulation. The system was able to detect stimulated dopamine release in vivo but not endogenous levels of dopamine.


Assuntos
Encéfalo/metabolismo , Catecolaminas/análise , Dopamina/análise , Eletroquímica/métodos , Eletrodos , Eletroforese em Microchip/métodos , Levodopa/análise , Animais , Catecolaminas/isolamento & purificação , Dopamina/isolamento & purificação , Levodopa/isolamento & purificação , Masculino , Ratos , Ratos Sprague-Dawley
17.
Mikrochim Acta ; 187(2): 143, 2020 01 21.
Artigo em Inglês | MEDLINE | ID: mdl-31965337

RESUMO

Four CeO2 nanomaterials with the morphologies of a nanoplate (CeO2-p), a nanocube (CeO2-c), a porous triangular microplate (CeO2-t), and of a porous hierarchical rod-stacked nanobundle (CeO2-b) were synthesized using a hydrothermal method. They were characterized by scanning and transmission electron microscopies, X-ray diffraction and X-ray photoelectron spectroscopy. Electrochemical characterizations reveal the tuning of their morphology and the presence of exposed crystal planes of CeO2 that can be realized by changing the alkali sources. Among these materials, the CeO2-b features the largest specific surface and lowest electron transfer resistance towards the redox probe Fe(CN)63-/4-. The best voltammetric response to dopamine and epinephrine is thus achieved by using the Nafion-CeO2-b coated electrode. A sensitive and selective method was developed that can voltammetrically detect dopamine (with a peak near 0.13 V vs. SCE), and epinephrine (with a peak near 0.25 V vs. SCE). The detection limits are 2.9 and 0.67 nM, respectively. Graphical abstractSchematic representation of morphology tailoring of CeO2 and electrochemical sensing of dopamine and epinephrine on these CeO2 samples with different morphologies.


Assuntos
Cério/química , Dopamina/análise , Técnicas Eletroquímicas/métodos , Epinefrina/análise , Eletrodos , Humanos , Limite de Detecção , Nanoestruturas/química , Oxirredução
18.
Talanta ; 210: 120626, 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-31987198

RESUMO

In this work, poly(sodium 4-styrenesulfonate)-functionalized three-dimensional graphene (PFSG) composites were realized via a facile and green strategy. The nanocomposite was characterized by scanning electron microscopy, ultraviolet and visible spectroscopy, X-ray photoelectron spectroscopy, and electrochemical method. An electroanalytical sensor of dopamine (DA) with high sensitivity and selectivity was fabricated based on PFSG modified glassy carbon electrode (GCE). Under the optimum conditions, the negatively charged PFSG composites exhibit strong electrostatic attraction for DA and electrostatic repulsion to the negatively charged ascorbic acid (AA) and uric acid (UA) molecules. Such electrostatic interaction hindered the enrichment of AA and UA on the surface of PSFG/GCE, which make a higher selectivity for the DA even in the presence of 120-fold AA and UA. Owing to the enhanced electron transfer rate and the stronger surface attraction, the current signal of DA on PFSG/GCE was about 160 times enhanced compared with the bare electrode. There was a good linear relationship between the reduction peak current of DA and concentration across the range of 0.002-2.0 µmol L-1 and 2.0-10.0 µmol L-1 with the limit of 0.8 nmol L-1. Further, the PFSG/GCE was applied to the detection of DA in human serum samples. This biosensor is simple, sensitive, selective and highly stable, which provided a new design strategy and a valuable tool to detect DA in complex samples.


Assuntos
Ácido Ascórbico/química , Dopamina/análise , Ácido Úrico/química , Eletrodos , Grafite/química , Concentração de Íons de Hidrogênio , Tamanho da Partícula , Poliestirenos/química , Eletricidade Estática , Propriedades de Superfície
19.
Anal Chim Acta ; 1098: 102-109, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31948572

RESUMO

Ratiometric analysis of dopamine (DA) in complex biological system is urgently desired. In this work, a novel dual-emission fluorescence probe was fabricated by embedding both gold nanoclusters (AuNCs) and poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) dots into zeolitic imidazolate framework-8 (ZIF-8) (abbreviated as ZIF-8@AuNCs-PFO) and applied to ratiometric analysis of DA. Remarkably, encapsulating AuNCs and PFO dots into ZIF-8 not only achieved an excellent aggregation induced emission (AIE) enhancement effect on AuNCs (5 times increase), but also brought about an unique DA-triggered asynchronous fluorescence changes of AuNCs and PFO dots. The as-prepared probe exhibited excellent performance toward DA in the concentrations range from 0.01 to 10000 µmol L-1 and good selectivity over interfering substances. The detection limit of DA was as low as 4.8 nmol L-1. Furthermore, good stability and practicability of the probe in human serum samples suggesting its great potential for diagnostic purposes. Moreover, the quenching mechanism of AuNCs was intensively studied and summarized as three synergistic processes: (i) electron transfer between AuNCs and DA; (ii) DA-triggered architecture change of ZIF-8; (iii) fluorescence resonance energy transfer (FRET) between AuNCs and polydopamine (PDA), which offered an important theory for ZIF-based fluorescent probes.


Assuntos
Dopamina/análise , Fluorenos/química , Corantes Fluorescentes/química , Ouro/química , Nanopartículas Metálicas/química , Pontos Quânticos/química , Zeolitas/química , Humanos , Estrutura Molecular , Tamanho da Partícula , Propriedades de Superfície
20.
Analyst ; 145(4): 1158-1168, 2020 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-31922176

RESUMO

Fast-scan cyclic voltammetry (FSCV) is used with carbon-fiber microelectrodes for the real-time detection of neurotransmitters on the subsecond time scale. With FSCV, the potential is ramped up from a holding potential to a switching potential and back, usually at a 400 V s-1 scan rate and a frequency of 10 Hz. The plot of current vs. applied potential, the cyclic voltammogram (CV), has a very different shape for FSCV than for traditional cyclic voltammetry collected at scan rates which are 1000-fold slower. Here, we explore the theory of FSCV, with a focus on dopamine detection. First, we examine the shape of the CVs. Background currents, which are 100-fold higher than faradaic currents, are subtracted out. Peak separation is primarily due to slow electron transfer kinetics, while the symmetrical peak shape is due to exhaustive electrolysis of all the adsorbed neurotransmitters. Second, we explain the origins of the dopamine waveform, and the factors that limit the holding potential (oxygen reduction), switching potential (water oxidation), scan rate (electrode instability), and repetition rate (adsorption). Third, we discuss data analysis, from data visualization with color plots, to the automated algorithms like principal components regression that distinguish dopamine from pH changes. Finally, newer applications are discussed, including optimization of waveforms for analyte selectivity, carbon nanomaterial electrodes that trap dopamine, and basal level measurements that facilitate neurotransmitter measurements on a longer time scale. FSCV theory is complex, but understanding it enables better development of new techniques to monitor neurotransmitters in vivo.


Assuntos
Dopamina/análise , Eletroquímica/métodos , Animais , Análise de Dados , Dopamina/química , Humanos , Fatores de Tempo
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