Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 4.557
Filtrar
1.
Pediatr Blood Cancer ; 67(2): e28081, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31724812

RESUMO

BACKGROUND: Neuroblastoma, the most common extracranial solid tumor of childhood, produces catecholamines that are metabolized within tumor cells. Homovanillic acid (HVA) and vanillylmandelic acid (VMA), the end products of catecholamine metabolism, have limited accuracy for testing of the tumors. This study assessed whether metabolites produced in earlier steps of catecholamine metabolism might offer improved diagnostic accuracy over urinary HVA and VMA. PROCEDURE: Plasma concentrations of 3-methoxytyramine, normetanephrine, and metanephrine were measured in two pediatric cohorts: (i) 96 children with confirmed neuroblastoma and (ii) 41 children with signs and symptoms of a catecholamine-producing tumor or other neoplasms and in whom neuroblastoma was excluded. Additional measurements of plasma 3-O-methyldopa and relationships of metabolites to MYCN amplification were examined in patient subgroups. RESULTS: Overall, 94 of the 96 patients with neuroblastoma had concentrations of 3-methoxytyramine or normetanephrine above age-specific upper limits of reference intervals, providing a diagnostic sensitivity of 97.9% that was higher (P < 0.0001) than that of 82.2% for HVA and VMA. One of the two patients with normal plasma results showed an elevation of plasma 3-O-methyldopa. Diagnostic specificities were, respectively, 95.1% and 84.8%. Areas under receiver-operating characteristic curves confirmed the superior diagnostic power of the plasma than the urinary test (0.994 vs 0.945; P = 0.0095). Ratios of plasma 3-methoxytyramine to normetanephrine were 7.2-fold higher (P < 0.0001) for patients who had neuroblastomas with MYCN amplification than without MYCN amplification. CONCLUSIONS: Measurements of plasma 3-methoxytyramine and normetanephrine provide a highly accurate diagnostic test for neuroblastoma and also offer potential for prognostic risk stratification.


Assuntos
Biomarcadores Tumorais/análise , Dopamina/análogos & derivados , Neuroblastoma/diagnóstico , Normetanefrina/análise , Tirosina/análogos & derivados , Adolescente , Estudos de Casos e Controles , Criança , Pré-Escolar , Dopamina/análise , Feminino , Seguimentos , Humanos , Lactente , Masculino , Neuroblastoma/sangue , Neuroblastoma/urina , Prognóstico , Estudos Retrospectivos , Tirosina/análise
2.
Arch Environ Contam Toxicol ; 78(2): 230-244, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31686138

RESUMO

In flowing environments, the degree of turbulent flow determines the movement and distribution of chemicals. Variation in flow alters the patchiness of toxicant plumes within a stream ecosystem. This patchiness translates into variability in exposure pulses for organisms encountering the toxic plume. Throughout a stream, the processes that give rise to chemical plume structure will vary as a function of local flow characteristics. This research examines the influence of toxicant mode of entry and stream flow velocity on the spatiotemporal patterning of exposure. Two introduction treatments were evaluated: one mimicking groundwater and the other mimicking runoff. The influence of flow regime was examined through the comparison of models constructed under two stream flow velocities. Concentrations of a tracer molecule were recorded using an electrochemical monitoring system. From these localized, direct measurements, geographic information systems (GIS) were used to model exposure throughout the stream. Conceptualizing exposure as a series of toxicant pulses, exposure can be defined using a variety of chemical peak characteristics. Three-dimensional, layered maps were constructed defining exposure as the integrated area of toxicant peaks, the magnitude of peaks, and peak frequency. Differences in the spatial and temporal patterning of exposure were apparent both within treatments and between treatments. No two definitions of exposure yielded the same exposure distributions for any treatment. These models demonstrate that distribution of chemical exposure throughout a stream ecosystem is linked to both toxicant mode of introduction and stream hydrodynamics. Furthermore, these results demonstrate that optimal exposure modeling relies on first defining exposure.


Assuntos
Ecotoxicologia/métodos , Sistemas de Informação Geográfica , Rios/química , Poluentes Químicos da Água/análise , Dopamina/análise , Ecossistema , Água Subterrânea/análise , Água Subterrânea/química , Análise Espaço-Temporal , Poluentes Químicos da Água/toxicidade
3.
Talanta ; 207: 120296, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31594571

RESUMO

Carbon materials and the metal nanocrystals enclosed by high-index facets have aroused considerable attention due to their large specific surface area, excellent electrical properties and catalysis activity, and easy accessibility for target molecules. In this study, the Pt concave nanocube (CNC) with high-index {410} and {510} facets was successfully prepared via a simple hydrothermal method. The multiwalled carbon nanotubes (MWCNT) and graphene oxide (GO) were chosen as the supporting materials to further improve the dispersion of Pt CNC and the electrical conductivity of nanocomposite. The nanocomposite was used to modify electrode for sensitive simultaneous detection dopamine and uric acid. The cyclic voltammetry and differential pulse voltammetry were applied to confirm the catalytic activity of proposed sensor. By using the as-synthesized nanomaterial as nonenzymatic sensing material, dopamine and uric acid can be detected with high sensitivity and selectivity. The linear range towards dopamine sensing is from 0.8 to 300 µM, and the limit of detection is 0.27 µM. For uric acid sensing, the sensor exhibited over two wide linear ranges (from 1 µM to 0.3 mM and from 0.3 mM to 1 mM) with a detection limit of 0.35 µM. The sensor also possessed a long-term stability, good reproducibility and a promising application for electrochemical detection of both dopamine and uric acid in real samples.


Assuntos
Dopamina/análise , Eletroquímica/instrumentação , Grafite/química , Limite de Detecção , Nanotubos de Carbono/química , Platina/química , Ácido Úrico/análise , Dopamina/química , Eletrodos , Modelos Moleculares , Conformação Molecular , Nanocompostos/química , Fatores de Tempo , Ácido Úrico/química
4.
Talanta ; 207: 120318, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31594597

RESUMO

This study designed a simplistic, efficient, and greener procedure to synthesize CeO2-CNTs. The analysis of structural and morphological characteristics of nano-composites has been done with regard to different procedures (e.g., EDX, XRD, & FESEM). In addition, simultaneous detection of ascorbic acid (AA), dopamine (DA), uric acid (UA) and acetaminophen (AC) has been examined at the modified glassy carbon electrode with CeO2-CNTs nano-composites. The surface area and electron transfer speed of the interplay between neuro-transmitters and electrode may be efficiently enhanced due to the existence of CeO2 nano-particles on CNTs surfaces. Moreover, electro-chemical behavior of electrodes has been dealt with by differential pulse voltammetry (DPV), impedance analysis (EIS), and cyclic voltammetry (CV). Acceptable linear response of AA, DA, UA and AC respectively have been ranged 0.01-900.0 µM, 0.01-700.0 µM, 0.01-900.0 µM, and 0.01-900.0 µM with determination limits (S/N = 3) of 3.1 nM, 2.6 nM, 2.4 nM and 4.4 nM. Ultimately, this procedure was used with successful results for determining AA, DA, UA and AC in real specimens, which suggested probable uses in other sensing studies.


Assuntos
Acetaminofen/análise , Ácido Ascórbico/análise , Cério/química , Dopamina/análise , Micro-Ondas , Nanotubos de Carbono/química , Ácido Úrico/análise , Acetaminofen/química , Ácido Ascórbico/química , Dopamina/química , Eletroquímica , Eletrodos , Química Verde , Concentração de Íons de Hidrogênio , Limite de Detecção , Nanopartículas/química , Nanotecnologia , Propriedades de Superfície , Fatores de Tempo , Ácido Úrico/química
5.
Anal Chim Acta ; 1096: 26-33, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31883588

RESUMO

Accurate and sensitive detection of dopamine (DA) is fundamental to monitor and diagnose certain neurological diseases. Herein, highly ordered mesoporous ZnFe2O4 (OM-ZnFe2O4) is prepared via a facile nanocasting method and shows the highly sensitive in the electrochemical detection of DA. The optimized OM-ZnFe2O4-40 shows the most excellent activity for DA oxidation in a wide linear range from 2 to 600 nM with a quick response time of 5 s, high sensitivity of 0.094 nA nM-1 and a lower detection limit of 0.4 nM (S/N = 3). The electrode modified with OM-ZnFe2O4 is further successfully used to monitor the increase of DA concentration induced by K+-stimulation of living PC12 cells in a neurological environment. This work offers a simple and powerful strategy for designing electrodes for detecting DA in biological systems.


Assuntos
Dopamina/análise , Técnicas Eletroquímicas/instrumentação , Compostos Férricos/química , Compostos de Zinco/química , Animais , Técnicas Eletroquímicas/métodos , Desenho de Equipamento , Limite de Detecção , Células PC12 , Porosidade , Ratos
6.
Mikrochim Acta ; 186(12): 762, 2019 11 11.
Artigo em Inglês | MEDLINE | ID: mdl-31712906

RESUMO

The metal-organic frameworks MIL-101 and sulfo-MIL-101 were used to modify graphite paste electrodes (GPEs) to obtain sensors for determination of dopamine (DA). Taking advantage of the catalytic activity of metal-organic frameworks (MOFs) and of the electrical conductivity of graphite, the modified GPEs show enhanced voltammetric responses, and the GPE modified with the sulfo-MOF displays superior sensitivity when operated at a working potential of -0.4 to 0.8 V (vs. Ag/AgCl). The sensor works in the 0.07 to100 µM DA concentration range and has a 43 nM detection limit. It is concluded that the sulfo group provides open sites for efficient electrostatic and hydrogen bonding interactions, which facilitates electron transfer. Graphical abstractSchematic representation of the structure of the sulfo-functionalized MOF (sulfo-MIL-101) and the different voltammetric signals of dopamine at the graphite paste electrodes (GPEs) modified with sulfo-MIL-101 and the parent MOF (MIL-101).


Assuntos
Dopamina/análise , Técnicas Eletroquímicas/instrumentação , Grafite/química , Estruturas Metalorgânicas/química , Dopamina/química , Técnicas Eletroquímicas/métodos , Eletrodos , Limite de Detecção , Oxirredução
7.
Anal Chim Acta ; 1091: 40-49, 2019 Dec 24.
Artigo em Inglês | MEDLINE | ID: mdl-31679573

RESUMO

We report here simple synthetic method for preparing polymer dots (Pdots) via hydrothermal treatment of organic dye (neutral red), urea and trisodium citrate. The prepared Pdots with enhanced quantum yield (quantum yield: 30.2%) was used as a selective and sensitive probe for fluorescent sensing of dopamine (DA) with high selectivity and sensitivity. The as-synthesized Pdots exhibited strong fluorescence intensity at 435 nm, which DA can trigger remarkable fluorescence quenching of such luminescent Pdots on the basis of inner filter effect (IFE) and static quenching effect (SQE). A wide linearity range (0.001 µM-900 µM) for DA detection was obtained with lower DL (3 S/N) of 0.28 nM, and no interference from other molecules such as ascorbic acid, urine acid, glutathione, glucose, epinephrine, arginine, cysteine, proline, creatinine, serine; alanine, L-therionine, Hg2+, Mg2+, K+, Ca2+ and Na+. The designed sensor was successfully applied in the imaging of DA in single living PC12 cells using droplet microfluidic approach, indicating its acceptable practicability of the proposed assay for DA detection with ultrahigh sensitivity in biological samples.


Assuntos
Dopamina/análise , Neurônios Dopaminérgicos/química , Corantes Fluorescentes/química , Polímeros/química , Pontos Quânticos/química , Animais , Corantes Fluorescentes/toxicidade , Dispositivos Lab-On-A-Chip , Limite de Detecção , Técnicas Analíticas Microfluídicas/instrumentação , Técnicas Analíticas Microfluídicas/métodos , Microscopia de Fluorescência/métodos , Células PC12 , Polímeros/toxicidade , Pontos Quânticos/toxicidade , Ratos , Análise de Célula Única/instrumentação , Análise de Célula Única/métodos
8.
ACS Appl Mater Interfaces ; 11(40): 36469-36475, 2019 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-31544453

RESUMO

The development of low cost, portable, and disposable biosensors for equipment-free and naked-eye biosensing is in eager demand for their widespread application in biomedical field, but it is still a challenge. Herein, we propose a novel paper analytical device (PAD) for truly equipment-free and naked-eye biosensing using dopamine as the chromogenic agent based on target-initiated catalyzed oxidation reaction. The dopamine-functionalized PAD (DPAD) possesses a significant three-dimensional net structure, excellent hydrophilicity, and unique response toward G-quadruplex DNAs against other DNAs, benefiting the bio/chemo reaction occurrence to assay target biomolecules. In light of the exceptional properties, the fabricated DPAD was applied in the analysis of Dam MTase through target-triggered exponential isothermal amplification. The recognition and methylation of H1 by Dam MTase contribute to formation of abundant hemin/G-quadruplexes, which catalyze oxidation of dopamine into dopachrome and reduce the dopamine amount on the DPAD surface. In comparison with the case in which Dam MTase is absent, an evident deep pink signal originating from dopachrome is observed directly by the naked eye and relied on Dam MTase concentrations. Therefore, truly equipment-free and naked-eye detection of Dam MTase is achieved with a detection limit of 1.46 U/mL. The fabricated DPAD not only achieves Dam MTase-visualized detection but also permits the accurate determination of other analytes by varying recognizable DNA's sequences, thus offering a universal biosensor and depicting significant potential for widespread applications in biomedical field.


Assuntos
Técnicas Biossensoriais/instrumentação , Técnicas Biossensoriais/métodos , Dopamina/análise , Papel , Catálise , Quadruplex G , Metiltransferases/metabolismo , Oxirredução
9.
Mikrochim Acta ; 186(9): 660, 2019 08 30.
Artigo em Inglês | MEDLINE | ID: mdl-31471825

RESUMO

A pyrolytic method is described for preparation of ultrafine Fe3C nanoparticles incorporated into N-doped graphitic carbon nanosheets (Fe3C@NGCSs). Iron phthalocyanine and graphitic carbon nitride (g-C3N4) are used as starting materials. The hybrid nanocomposite was placed on a glassy carbon electrode (GCE) and then applied to simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA) and xanthine (XA). Figures of merits are as follows: for AA, the linear response range covers the 54.0-5491.0 µM range, the lower detection limit is 16.7 µM, and the best working voltage (vs. the saturated calomel electrode (SCE)) is 0.05 V. The respective data for DA are 1.2-120.8 µM, 0.34 µM and 0.19 V (vs. SCE). For UA, the respective data are 4.8-263.0 µM, 1.4 µM and 0.32 V (vs. SCE), and for XA the data are 4.8-361.0 µM, 1.5 µM and 0.71 V (vs. SCE). The method was successfully applied to their simultaneous determination in spiked serum samples. Graphical abstract Ultrafine Fe3C nanoparticles embedded in N-doped graphitic carbon sheets for simultaneous determination of ascorbic acid, dopamine, uric acid and xanthine.


Assuntos
Ácido Ascórbico/análise , Compostos Inorgânicos de Carbono/química , Dopamina/análise , Compostos de Ferro/química , Nanopartículas/química , Ácido Úrico/análise , Xantina/análise , Técnicas Biossensoriais , Carbono/química , Técnicas Eletroquímicas , Eletrodos , Humanos , Tamanho da Partícula , Propriedades de Superfície
10.
Mikrochim Acta ; 186(9): 602, 2019 08 04.
Artigo em Inglês | MEDLINE | ID: mdl-31377866

RESUMO

Considering the importance of dopamine (DA) detection for neuroscience and disease diagnosis, herein, an electrochemical sensor for dopamine is described. It is based on the use of a Ni-Co-P nanostructure fabricated on nickel foam via electrode position from cobalt chloride and ammonium phosphate for 10 min. Time-dependent experiments show the transformation of Ni-Co-P nanoparticles to spheres. The resulting electrode display excellent electrochemical response to DA. Figures of merit include (a) a working potential of 0.55 V (vs. Ag/AgCl); (b) an electrochemical sensitivity of 5262 µA mM-1 cm-2; (c) a wide linear range (from 0.5 to 2350 µM), and (d) a 1 µM detection limit. The outstanding electrochemical performance is explained by the synergistic effects of large surface area, improved electron transfer, presence of free binders, and the presence of three active components (nickel, cobalt and phosphonium ion). Graphical abstract A Ni-Co-P nanostructure was electrodeposited on nickel foam to obtain an electrochemical sensor for amperometric determination of dopamine with outstanding performance.


Assuntos
Cobalto/química , Dopamina/análise , Galvanoplastia , Níquel/química , Fósforo/química , Eletrodos , Nanoestruturas/química , Tamanho da Partícula , Propriedades de Superfície
11.
ACS Appl Mater Interfaces ; 11(37): 34497-34506, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31449380

RESUMO

The rapidly developing field of conducting polymers in organic electronics has many implications for bioelectronics. For biosensing applications, tailoring the functionalities of the conducting polymer's surface is an efficient approach to improve both sensitivity and selectivity. Here, we demonstrated a facile and economic approach for the fabrication of a high-density, negatively charged carboxylic-acid-group-functionalized PEDOT (PEDOT:COOH) using an inexpensive ternary carboxylic acid, citrate, as a dopant. The polymerization efficiency was significantly improved by the addition of LiClO4 as a supporting electrolyte yielding a dense PEDOT:COOH sensing interface. The resulting PEDOT:COOH interface had a high surface density of carboxylic acid groups of 0.129 µmol/cm2 as quantified by the toluidine blue O (TBO) staining technique. The dopamine response measured with the PEDOT:COOH sensing interface was characterized by cyclic voltammetry with a significantly reduced ΔEp of 90 mV and a 3-fold increase in the Ipa value compared with those of the nonfunctionalized PEDOT sensing interface. Moreover, the cyclic voltammetry and electrochemical impedance spectroscopy results demonstrated the increased electrode kinetics and highly selective discrimination of dopamine (DA) in the presence of the interferents ascorbic acid (AA) and uric acid (UA), which resulted from the introduction of negatively charged carboxylic acid groups. The negatively charged carboxylic acid groups could favor the transfer, preconcentration, and permeation of positively charged DA to deliver improved sensing performance while repelling the negatively charged AA and UA interferents. The PEDOT:COOH interface facilitated measurement of dopamine over the range of 1-85 µM, with a sensitivity of 0.228 µA µM-1, which is 4.1 times higher than that of a nonfunctionalized PEDOT electrode (0.055 µA µM-1). Our results demonstrate the feasibility of a simple and economic fabrication of a high-density PEDOT:COOH interface for chemical sensing, which also has the potential for coupling with other biorecognition molecules via carboxylic acid moieties for the development of a range of advanced PEDOT-based biosensors.


Assuntos
Compostos Bicíclicos Heterocíclicos com Pontes/química , Ácido Cítrico/química , Dopamina/análise , Técnicas Eletroquímicas , Polímeros/química , Ácido Ascórbico/química , Limite de Detecção , Ácido Úrico/química
12.
Mar Drugs ; 17(9)2019 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-31443523

RESUMO

Abstract: α-Conotoxin TxIB is a specific antagonist of α6/α3ß2ß3(α6ß2*) nicotinic acetylcholine receptor (nAChR) with an IC50 of 28 nM. Previous studies have shown that α6ß2* nAChRs are abundantly expressed in midbrain dopaminergic neurons and play an important role in mediating the mechanism of nicotine and other drugs reward effect. It provided important targets for the development of anti-addiction drugs. The present study evaluated the pharmacological activity of TxIB in vivo with conditioned place preference (CPP) model, which were induced by subcutaneous injection (s.c.) of nicotine (NIC, 0.5 mg/kg). α-Conotoxin TxIB inhibited the expression and reinstatement of CPP in mice dose-dependently, but had no significant effect on locomotor activity. The concentrations of dopamine (DA), γ-aminobutyric acid (GABA) and noradrenaline (NE) in different brain regions were measured by enzyme-linked immunosorbent assay (ELISA). We found that TxIB could inhibit the concentrations of DA, GABA and NE in different brain regions (such as nucleus accumbens (NAc), hippocampus (HIP) and prefrontal cortex (PFC)) in NIC-induced mice. The concentrations of DA and NE were decreased in ventral tegmental area (VTA), while GABA had little change. The current work described the inhibition activity of TxIB in NIC-induced CPP, suggesting that α6ß2* nAChR-targeted compound may be a promising drug for nicotine addiction treatment.


Assuntos
Condicionamento Psicológico/efeitos dos fármacos , Conotoxinas/farmacologia , Antagonistas Nicotínicos/farmacologia , Receptores Nicotínicos/metabolismo , Tabagismo/tratamento farmacológico , Animais , Técnicas de Observação do Comportamento , Comportamento Animal/efeitos dos fármacos , Conotoxinas/uso terapêutico , Modelos Animais de Doenças , Dopamina/análise , Dopamina/metabolismo , Humanos , Injeções Subcutâneas , Ligantes , Masculino , Camundongos , Nicotina/administração & dosagem , Nicotina/efeitos adversos , Antagonistas Nicotínicos/uso terapêutico , Norepinefrina/análise , Norepinefrina/metabolismo , Recompensa , Área Tegmentar Ventral/química , Área Tegmentar Ventral/efeitos dos fármacos , Área Tegmentar Ventral/metabolismo , Ácido gama-Aminobutírico/análise , Ácido gama-Aminobutírico/metabolismo
13.
Mikrochim Acta ; 186(9): 618, 2019 08 13.
Artigo em Inglês | MEDLINE | ID: mdl-31410617

RESUMO

A colorimetric/fluorometric dual-signal assay is described for the determination of dopamine (DA). A nanoprobe was obtained by linking a 4-(4-dialkylaminostyryl)pyridinium derived fluorophore to citrate-capped gold nanoparticles (AuNPs). The fluorescence of the fluorophore is quenched by the AuNPs via fluorescence resonance energy transfe. In the presence of DA, the catechol group of DA can absorb on the surface of AuNPs to induce aggregation, which is accompanied by a color change from red to blue. The yellow fluorescence of the fluorophore with excitation/emission maximum at 365/570 nm is recovered. The dual-signal detection allows the quantitative analysis of DA within 300 µM by the colorimetric method and 80 µM by the fluorometric method. The detection limits for the colorimetric/fluorometric methods are 1.85 µM and 0.29 µM, respectively. Quantitative determination of DA in spiked urine samples was successfully demonstrated, with recoveries ranging from 98.2 to 106.0%. Graphical abstract A colorimetric/fluorometric dual-signal assay is described for the determination of dopamine by linking a fluorophore to gold nanoparticles. The dopamine causes aggregation of the nanoparticles to induce color change, which is followed by the recovery of the fluorescence.


Assuntos
Ácido Cítrico/química , Dopamina/análise , Transferência Ressonante de Energia de Fluorescência , Corantes Fluorescentes/química , Ouro/química , Nanopartículas Metálicas/química , Piridinas/química , Cor , Colorimetria , Dopamina/química
14.
Parasit Vectors ; 12(1): 397, 2019 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-31399119

RESUMO

BACKGROUND: La Crosse virus (LACV) infection has been shown to manipulate the blood-feeding behaviors of its main vector, Aedes triseriatus. Here, we investigated the effects of virus infection on serotonin and dopamine and their potential roles in host-seeking. In mosquitoes, serotonin depletion has been shown to interfere with blood-feeding but not host-seeking. Dopamine depletion does not affect either blood-feeding or host-seeking; elevations of dopamine, however, has been shown to inhibit host-seeking. The purpose of this study was to determine the effects of LACV infection on the host-seeking behavior of and neurotransmitter levels in Ae. triseriatus. METHODS: Host-seeking behavior was evaluated using a uni-port olfactometer and a membrane feeder assay. Levels of serotonin and dopamine in infected and control mosquito heads were measured using HPLC-ED. RESULTS: Infection with LACV significantly inhibited the activation and attraction of Ae. triseriatus females to a host. A higher proportion of uninfected Ae. triseriatus females were activated by the presence of a host compared to infected mosquitoes and more uninfected mosquitoes were full responders (95.7%) compared to infected ones (91.1%). However, infection with LACV did not significantly affect the landing, probing, or blood-feeding rates of female mosquitoes. LACV-infected mosquitoes had lower serotonin levels than controls (104.5 vs 138.3 pg/head) while the dopamine levels were not affected by infection status (282.3 vs 237 pg/head). CONCLUSIONS: Our work suggests that virus-induced reduction of serotonin is related to previously reported blood-feeding alterations in LACV-infected mosquitoes and could lead to enhanced transmission and increased vectorial capacity. In addition, some aspects of host-seeking were inhibited by virus infection.


Assuntos
Aedes/química , Aedes/virologia , Encefalite da Califórnia/virologia , Comportamento Alimentar , Comportamento de Busca por Hospedeiro , Neurotransmissores/análise , Animais , Dopamina/análise , Feminino , Vírus La Crosse/fisiologia , Controle de Mosquitos , Mosquitos Vetores/química , Mosquitos Vetores/virologia , Olfatometria , Serotonina/análise
15.
Mikrochim Acta ; 186(9): 607, 2019 08 06.
Artigo em Inglês | MEDLINE | ID: mdl-31388771

RESUMO

Development of novel nanomaterials for biosensors has intrigued widespread interest. Here, we report a method to graft the redox-active dye Methylene Blue (MB) onto molybdenum disulfide (MoS2) nanosheet surface via electrostatic and π-stacking interaction. The adsorption of MB on nanosheets was investigated by atomic force microscopy (AFM), which proved that the adsorption isotherm fits a Temkin not a Langmuir model. After studying the electrochemical properties of MB-decorated MoS2 nanocomposite (MoS2@MB) on a glassy carbon electrode (GCE), an electrochemical sensor for microRNA-21 detection was designed. The modified GCE can quantify microRNA-21 in concentrations as low as 68 fM, typically at a working potential of -0.28 V (vs. SCE). The same modified electrode also shows outstanding electrocatalytic ability towards individual and simultaneous determination of dopamine (DA) and uric acid (UA) with electrochemical peaks at 0.16 V (DA) and 0.45 V (UA). The detection limits for simultaneous determination are 0.58 µM for DA and 0.91 µM for UA, respectively. Graphical abstract A powerful sensing electrode was obtained by grafting Methylene Blue (MB) on molybdenum disulfide (MoS2@MB) nanosheet surface. Such MoS2@MB-based electrochemical sensor was used to label-free detect microRNA and simultaneously determine dopamine and uric acid.


Assuntos
Técnicas Biossensoriais , Dopamina/análise , Técnicas Eletroquímicas , MicroRNAs/análise , Nanocompostos/química , Ácido Úrico/análise , Dissulfetos/química , Humanos , Azul de Metileno/química , Molibdênio/química , Tamanho da Partícula , Propriedades de Superfície
16.
Mikrochim Acta ; 186(8): 540, 2019 07 17.
Artigo em Inglês | MEDLINE | ID: mdl-31317272

RESUMO

The authors have modified a carbon paste electrode with Al2O3-supported palladium nanoparticles (PdNP@Al2O3) to obtain a sensor for simultaneous voltammetric determination of melatonin (MT), dopamine (DA) and acetaminophen (AC). The PdNP@Al2O3 was characterized by scanning electron microscopy and energy-dispersive X-ray spectra. The sensor can detect DA, AC, MT and their mixtures by giving distinct signals at working voltages of typically 236, 480 and 650 mV (vs. Ag/AgCl), respectively. Differential pulse voltammetric peak currents of DA, AC and MT increase linearly in the 50 nmol L-1 - 1.45 mmol L-1, 40 nmol L-1 -1.4 mmol L-1, and 6.0 nmol L-1 - 1.4 mmol L-1 concentration ranges. The limits of detection are 36.5 nmol L-1 for DA, 36.5 nmol L-1 for AC, and 21.6 nmol L-1 for MT. The sensor was successfully used to detect the analytes in (spiked) human serum and drug samples. Graphical abstract Schematic presentation of Al2O3-supported palladium nanoparticles (PdNP@Al2O3) for modification of a carbon paste electrode (CPE) to develop a voltammetric sensor for the simultaneous determination of dopamine (DA), acetaminophen (AC) and melatonin (MT).


Assuntos
Acetaminofen/análise , Óxido de Alumínio/química , Dopamina/análise , Melatonina/análise , Nanopartículas Metálicas/química , Paládio/química , Acetaminofen/sangue , Acetaminofen/química , Acetaminofen/urina , Carbono/química , Dopamina/sangue , Dopamina/química , Dopamina/urina , Técnicas Eletroquímicas , Eletrodos , Humanos , Melatonina/sangue , Melatonina/química , Melatonina/urina
17.
Daru ; 27(2): 593-603, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31317442

RESUMO

BACKGROUND: Interest in functionalized carbon nanotubes for many applications arises from a variety on the kind of modification atoms or molecules that are attached to it. Dopamine, the feel-good hormone, release by neurons and playing an important role in body systems. Abnormal dopamine levels cause nerve disorders such as Parkinson's disease and schizophrenia. OBJECTIVES: The aim of this study was the design and fabrication of electrochemical sensor based on MWCNTs and Pd nanoparticles for detection and determination of dopamine in biological samples. METHODS: For this purpose, we report the synthesis of pramipexole-functionalized MWCNTs (pp-MWCNTs) for efficient capture of palladium nanoparticles and fabrication of Pd/pp-MWCNTs nanocomposite. Morphological and structural characteristics of the nanocomposites were characterized using various techniques including field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FT-IR). RESULTS: This newly synthesized nanocomposite may have numerous applications in nanotechnology and sensing. We show that the synthesized nanocomposite reported here will be applicable for modifications of bare glassy carbon electrode (Pd/pp-MWCNTs/GCE) to sense of dopamine electrochemically. Two linear calibrations for dopamine are obtained over ranges of 0.01 to 10 µM and 10 to 200 µM with a detection limit of 1.4 nM. The Pd/pp-MWCNTs/GCE shows high stability and sensitivity, and an acceptable decrease of over-potential for the electrooxidation of dopamine that decreases interference in the analysis. The proposed Pd/pp-MWCNTs nanocomposite can be used as a voltammetric detector for dopamine monitoring in routine real sample analysis. CONCLUSIONS: The proposed sensor showed high sensitivity and selectivity in sensing dopamine in biological samples. Graphical abstract Preparation of Pd/pp-MWCNTs/GCE for detection of dopamine.


Assuntos
Dopamina/análise , Paládio/química , Pramipexol/química , Animais , Humanos , Nanopartículas Metálicas , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Espectroscopia de Infravermelho com Transformada de Fourier
18.
Talanta ; 204: 475-483, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31357322

RESUMO

Laccase was immobilized on a glassy carbon electrode layered with multi-walled carbon nanotubes using a film of botryosphaeran, a fungal (1 → 3)(1 → 6)-ß-D-glucan. This novel biosensing platform was characterized by electrochemical impedance spectroscopy and scanning electron microscopy, and applied for the determination of dopamine. Experimental variables such as enzyme concentration, pH value and operational parameters of the electroanalytical technique were optimized. Using square-wave voltammetry, there was a linear dependence of peak current and dopamine concentration within the range of 2.99-38.5 µmol L-1 with a limit of detection of 0.127 µmol L-1. The biosensor was successfully applied in the determination of dopamine in pharmaceutical injection and synthetic biological samples, and presented good selectivity even in the presence of uric acid and ascorbic acid, as well as other phenolic compounds. The different aspects regarding the operational stability of the laccase biosensor were evaluated, demonstrating good intra-day and inter-day repeatability, and long-storage stability. Furthermore, this biosensor was evaluated in the indirect determination of spironolactone by using the analytical signal of dopamine, presenting a limit of detection of 0.94 µmol L-1. The results obtained in the analysis of spironolactone in commercial pharmaceutical samples were satisfactory.


Assuntos
Técnicas Biossensoriais/métodos , Dopamina/análise , Glucanos/química , Lacase/química , Espironolactona/análise , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Enzimas Imobilizadas/química , Limite de Detecção , Nanotubos de Carbono/química
19.
Anal Bioanal Chem ; 411(29): 7681-7688, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31286178

RESUMO

A new electrochemical sensor, based on NdFeO3 nanoparticles as electrocatalytic material, was proposed here for the detection of dopamine (DA). NdFeO3 nanoparticles were first synthesized by a simple thermal treatment method and subsequent annealing at high temperature (700 °C). The prepared electrocatalytic material has been characterized in detail by SEM-EDX, XRD, and Raman techniques. Characterization results display its sheet-like morphology, constituted by a porous network of very small orthorhombic NdFeO3 nanoparticles. NdFeO3 electrocatalytic material was then used to modify the working electrode of screen-printed carbon electrodes (SPCEs). Electrochemical tests demonstrated that NdFeO3- modified screen-printed carbon electrode (NdFeO3/SPCE) exhibited a remarkable enhancement of the dopamine electrooxidation, compared to the bare SPCE one. The analytical performance of the developed sensor has been evaluated for the detection of this analyte by means of the square-wave voltammetry (SWV) technique. The modified electrode showed two linear concentration ranges, from 0.5 to 100 µM and 150 to 400 µM, respectively, a limit of detection (LOD) of 0.27 µM (at S/N = 3), and good reproducibility, stability, and selectivity. Additionally, we also report an attempt made to propose the modified sensor for the simultaneous detection of dopamine and uric acid (UA). The procedure was also applied for the determination of dopamine in spiked real samples. So, this paper reports for the first time the use of a modified NdFeO3 screen-printed electrode for developing an electrochemical sensor for the quantification of important biomolecules. Graphical abstract.


Assuntos
Dopamina/análise , Técnicas Eletroquímicas/instrumentação , Compostos Férricos/química , Neodímio/química , Técnicas Biossensoriais , Catálise , Eletrodos , Humanos , Limite de Detecção , Reprodutibilidade dos Testes , Ácido Úrico/análise
20.
Food Chem ; 298: 125020, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31260965

RESUMO

Bioactive amines are found in food and can be relevant for the assessment of fruits shelf life and nutritional quality. The pulp and peel of 20 banana and plantain were analyzed and the bioactive amine content varied according to the genotype, ripening stage, fruit tissue and thermal processing. In most of the analyzed genotypes, tyramine, histamine, dopamine, serotonin, spermidine, and spermine were decreased during the ripening process in the pulps. By contrast, there was an increase in putrescine level. In many genotypes of plantains, the serotonin and dopamine contents in pulp decreased until stage 5 and increased at stage 7. Peels contain higher levels of serotonin, dopamine, histamine and tyramine than pulps. Additionally, thermal processing affects the content of amines present in fruit. Boiling with the peel should be preferred in domestic preparations, regardless of the genotype used.


Assuntos
Aminas/análise , Frutas/metabolismo , Musa/metabolismo , Plantago/metabolismo , Aminas Biogênicas/análise , Dopamina/análise , Frutas/química , Genótipo , Histamina/análise , Musa/química , Musa/genética , Plantago/química , Plantago/genética , Putrescina/análise , Serotonina/análise , Espermidina/análise , Espermina/análise , Temperatura , Tiramina/análise
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA