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1.
Nat Commun ; 11(1): 4772, 2020 09 24.
Artigo em Inglês | MEDLINE | ID: mdl-32973145

RESUMO

Surface-enhanced Raman spectroscopy (SERS) is a powerful tool for vibrational spectroscopy as it provides several orders of magnitude higher sensitivity than inherently weak spontaneous Raman scattering by exciting localized surface plasmon resonance (LSPR) on metal substrates. However, SERS can be unreliable for biomedical use since it sacrifices reproducibility, uniformity, biocompatibility, and durability due to its strong dependence on "hot spots", large photothermal heat generation, and easy oxidization. Here, we demonstrate the design, fabrication, and use of a metal-free (i.e., LSPR-free), topologically tailored nanostructure composed of porous carbon nanowires in an array as a SERS substrate to overcome all these problems. Specifically, it offers not only high signal enhancement (~106) due to its strong broadband charge-transfer resonance, but also extraordinarily high reproducibility due to the absence of hot spots, high durability due to no oxidization, and high compatibility to biomolecules due to its fluorescence quenching capability.


Assuntos
Carbono/química , Nanofios/química , Análise Espectral Raman/métodos , Fluorescência , Porosidade , Reprodutibilidade dos Testes , Ressonância de Plasmônio de Superfície/métodos , Propriedades de Superfície
2.
Yakugaku Zasshi ; 140(9): 1101-1106, 2020.
Artigo em Japonês | MEDLINE | ID: mdl-32879242

RESUMO

Organoselenium compounds have attracted significant interest because of their use as important reagents in organic syntheses and potential biological activities, necessitating the development of simple and general synthetic methods. This article reviews our studies to develop of copper-catalyzed C-Se bond formation reactions via cross coupling and C-H activation. A number of unsymmetrical and symmetrical diaryl selenides were synthesized via Se-arylation of diaryl diselenides or selenium powder with triarylbismuthanes under aerobic conditions, achieving moderate to excellent yields. When the reaction of triphenylbismuthane with elemental Se was monitored with gas chromatography, diphenyl diselenide and diphenyl selenide formation was confirmed. Subsequently, 1-pot 2-step reactions were performed under mild conditions to obtain 3-selanyl imidazo[1,2-a]pyridines from triarylbismuthanes and diimidazopyridyl diselenides, which were generated from imidazo[1,2-a]pyridines and Se powder, in good to excellent yields. It should be noted that all three aryl groups in the bismuth and both selanyl groups in the diaryl diselenide generated from the selenium source were transferred to the coupling products. Cu-catalyzed tandem cyclization of 2-(2-iodophenyl)imidazo[1,2-a]pyridines with selenium for the synthesis of benzo[b]selenophene-fused imidazo[1,2-a]pyridines is also described herein. The molecular structure of the tetracyclic compound features nearly coplanar rings, and the maximum absorption is red-shifted compared to those of imidazo[1,2-a]pyridine and benzoselenophene.


Assuntos
Carbono/química , Cobre/química , Hidrogênio/química , Compostos Organosselênicos/síntese química , Catálise , Ciclização , Ligação de Hidrogênio , Fenômenos de Química Orgânica
3.
J Chromatogr A ; 1626: 461328, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797818

RESUMO

Ferric oxide/carbon (Fe2O3@C) was fabricated via direct carbonization of metal-organic framework of iron (MOF-235) under argon atmosphere. The magnetic Fe2O3 nanoparticles are evenly embedded in porous carbon matrix, while original morphology of MOF-235 was well-maintained. The synthesized Fe2O3@C was used as magnetic sorbent for extracting five benzoylurea insecticides (BUs). The materials exhibited excellent extraction performance, which benefited not only from the strong π-π interaction and hydrophobic interaction (π-conjugated system), but also to the abundant adsorption sites and flexible transport channel (the interconnected 3D porous structure). A three-factor-three-level Box-Behnken design (BBD) was selected to optimize three greatly influential parameters: amount of adsorbent (A), desorption time (B) and volume of desorption solvent (C) by response surface methodology. The established method coupled to HPLC-UV detection showed wide linearity with the range of 0.2-450 µg•L-1, relatively low limits of detection (0.05-0.10 µg•L-1) with the relative standard deviation (RSD) (n = 7) lower t than 5.47%. Moreover, the proposed method was successfully applied to analyze BUs in tea samples and investigate the removal effect of different washing on BUs residues from tea leaf. These results indicated that the synthesized Fe2O3@C is a promising adsorbent material for magnetic solid phase extraction of BUs at trace concentrations from tea samples.


Assuntos
Inseticidas/análise , Nanopartículas de Magnetita/química , Estruturas Metalorgânicas/química , Chá/química , Ureia/análise , Adsorção , Carbono/química , Cromatografia Líquida de Alta Pressão/métodos , Cromatografia Líquida de Alta Pressão/normas , Compostos Férricos/química , Inseticidas/isolamento & purificação , Inseticidas/normas , Limite de Detecção , Porosidade , Padrões de Referência , Extração em Fase Sólida , Espectrofotometria Ultravioleta , Chá/metabolismo , Ureia/análogos & derivados , Ureia/isolamento & purificação , Ureia/normas
4.
Nat Commun ; 11(1): 3906, 2020 08 06.
Artigo em Inglês | MEDLINE | ID: mdl-32764563

RESUMO

Enzymatic hydroxylation of unactivated primary carbons is generally associated with the use of molecular oxygen as co-substrate for monooxygenases. However, in anaerobic cholesterol-degrading bacteria such as Sterolibacterium denitrificans the primary carbon of the isoprenoid side chain is oxidised to a carboxylate in the absence of oxygen. Here, we identify an enzymatic reaction sequence comprising two molybdenum-dependent hydroxylases and one ATP-dependent dehydratase that accomplish the hydroxylation of unactivated primary C26 methyl group of cholesterol with water: (i) hydroxylation of C25 to a tertiary alcohol, (ii) ATP-dependent dehydration to an alkene via a phosphorylated intermediate, (iii) hydroxylation of C26 to an allylic alcohol that is subsequently oxidised to the carboxylate. The three-step enzymatic reaction cascade divides the high activation energy barrier of primary C-H bond cleavage into three biologically feasible steps. This finding expands our knowledge of biological C-H activations beyond canonical oxygenase-dependent reactions.


Assuntos
Trifosfato de Adenosina/metabolismo , Betaproteobacteria/metabolismo , Anaerobiose , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Betaproteobacteria/genética , Carbono/química , Colestadienóis/química , Colestadienóis/metabolismo , Colesterol/química , Colesterol/metabolismo , Genes Bacterianos , Hidroliases/genética , Hidroliases/metabolismo , Hidroxilação , Oxigenases de Função Mista/genética , Oxigenases de Função Mista/metabolismo , Modelos Biológicos , Oxirredução , Filogenia , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Água/metabolismo
5.
Small ; 16(38): e2003010, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32815251

RESUMO

Currently, mesenchymal stem cells (MSCs)-based therapies for bone regeneration and treatments have gained significant attention in clinical research. Though many chemical and physical cues which influence the osteogenic differentiation of MSCs have been explored, scaffolds combining the benefits of Zn2+ ions and unique nanostructures may become an ideal interface to enhance osteogenic and anti-infective capabilities simultaneously. In this work, motivated by the enormous advantages of Zn-based metal-organic framework-derived nanocarbons, C-ZnO nanocarbons-modified fibrous scaffolds for stem cell-based osteogenic differentiation are constructed. The modified scaffolds show enhanced expression of alkaline phosphatase, bone sialoprotein, vinculin, and a larger cell spreading area. Meanwhile, the caging of ZnO nanoparticles can allow the slow release of Zn2+ ions, which not only activate various signaling pathways to guide osteogenic differentiation but also prevent the potential bacterial infection of implantable scaffolds. Overall, this study may provide new insight for designing stem cell-based nanostructured fibrous scaffolds with simultaneously enhanced osteogenic and anti-infective capabilities.


Assuntos
Carbono/química , Células-Tronco Mesenquimais/citologia , Nanofibras/química , Osteogênese/fisiologia , Tecidos Suporte/química , Óxido de Zinco/química , Fosfatase Alcalina/metabolismo , Diferenciação Celular/fisiologia , Células Cultivadas , Humanos , Sialoproteína de Ligação à Integrina/metabolismo , Teste de Materiais , Células-Tronco Mesenquimais/metabolismo , Microscopia Eletrônica de Varredura , Nanofibras/ultraestrutura , Transdução de Sinais , Engenharia Tecidual , Vinculina/metabolismo
6.
Proc Natl Acad Sci U S A ; 117(37): 22705-22711, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32839319

RESUMO

Black carbon (BC) aerosol plays an important role in the Earth's climate system because it absorbs solar radiation and therefore potentially warms the climate; however, BC can also act as a seed for cloud particles, which may offset much of its warming potential. If BC acts as an ice nucleating particle (INP), BC could affect the lifetime, albedo, and radiative properties of clouds containing both supercooled liquid water droplets and ice particles (mixed-phase clouds). Over 40% of global BC emissions are from biomass burning; however, the ability of biomass burning BC to act as an INP in mixed-phase cloud conditions is almost entirely unconstrained. To provide these observational constraints, we measured the contribution of BC to INP concentrations ([INP]) in real-world prescribed burns and wildfires. We found that BC contributes, at most, 10% to [INP] during these burns. From this, we developed a parameterization for biomass burning BC and combined it with a BC parameterization previously used for fossil fuel emissions. Applying these parameterizations to global model output, we find that the contribution of BC to potential [INP] relevant to mixed-phase clouds is ∼5% on a global average.


Assuntos
Carbono/química , Mudança Climática , Água/química , Incêndios Florestais , Aerossóis , Poluentes Atmosféricos/efeitos adversos , Poluentes Atmosféricos/química , Carbono/efeitos adversos , Gelo/análise , Estações do Ano
7.
Ecotoxicol Environ Saf ; 204: 111066, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32781344

RESUMO

In this study, an iron-doped metal-organic framework (MOF) Fe/ZIF-8 was synthesized from ZIF-8 at room temperature. Direct carbonization of Fe/ZIF-8 under a nitrogen atmosphere produced nanoporous nitrogen doped carbon nanoparticles decorated with Fe component (Fe/NC). The Fe/NC exhibited a large surface area (1221.185 m2 g-1) and narrow pore-size distribution (3-5 nm). The nanoporous Fe/NC components along with Nafion were used to modify a glassy carbon electrode for the electrochemical determination of chloramphenicol and metronidazole via linear sweep voltammetry. Under optimal conditions, the reduction peak currents (observed at -0.237 V and -0.071 V vs. Ag/AgCl) of these analytes increased linearly with increasing chloramphenicol and metronidazole concentrations in the range of 0.1-100 µM and 0.5-30 µM, with the detection limits estimated to be 31 nM and 165 nM, respectively. This result was attributed to the large surface area, porous structure, high nitrogen content, and as well as the electrocatalytic effect of Fe atoms embeded in the carbon support. The proposed sensor was used for chloramphenicol and metronidazole analysis in samples, providing satisfactory results.


Assuntos
Carbono/química , Cloranfenicol/análise , Técnicas Eletroquímicas/métodos , Ferro/química , Estruturas Metalorgânicas/química , Metronidazol/análise , Nitrogênio/química , Animais , Cloranfenicol/urina , Eletrodos , Humanos , Limite de Detecção , Metronidazol/urina , Leite/química , Nanoporos , Soluções Oftálmicas/química , Porosidade , Comprimidos/química
8.
Int J Nanomedicine ; 15: 5473-5489, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32801701

RESUMO

Introduction: Biofilms protect bacteria from antibiotics and this can produce drug-resistant strains, especially the main pathogen of periodontitis, Porphyromonas gingivalis. Carbon quantum dots with various biomedical properties are considered to have great application potential in antibacterial and anti-biofilm treatment. Methods: Tinidazole carbon quantum dots (TCDs) and metronidazole carbon quantum dots (MCDs) were prepared by a hydrothermal method with the clinical antibacterial drugs tinidazole and metronidazole, respectively. Then, TCDs and MCDs were characterized by transmission electron microscopy, UV-visible spectroscopy, infrared spectroscopy and energy-dispersive spectrometry. The antibacterial effects were also investigated under different conditions. Results: The TCDs and MCDs had uniform sizes. The results of UV-visible and energy-dispersive spectrometry confirmed their important carbon polymerization structures and the activity of the nitro group, which had an evident inhibitory effect on P. gingivalis, but almost no effect on other bacteria, including Escherichia coli, Staphylococcus aureus and Prevotella nigrescens. Importantly, the TCDs could penetrate the biofilms to further effectively inhibit the growth of P. gingivalis under the biofilms. Furthermore, it was found that the antibacterial effect of TCDs lies in its ability to impair toxicity by inhibiting the major virulence factors and related genes involved in the biofilm formation of P. gingivalis, thus affecting the self-assembly of biofilm-related proteins. Conclusion: The findings demonstrate a promising new method for improving the efficiency of periodontitis treatment by penetrating the P. gingivalis biofilm with preparations of nano-level antibacterial drugs.


Assuntos
Antibacterianos/química , Antibacterianos/farmacologia , Porphyromonas gingivalis/efeitos dos fármacos , Pontos Quânticos/química , Animais , Antibacterianos/efeitos adversos , Aderência Bacteriana/efeitos dos fármacos , Biofilmes/efeitos dos fármacos , Carbono/química , Carbono/farmacologia , Escherichia coli/efeitos dos fármacos , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Humanos , Metronidazol/química , Metronidazol/farmacologia , Testes de Sensibilidade Microbiana , Microscopia Eletrônica de Transmissão , Periodontite/microbiologia , Porphyromonas gingivalis/genética , Porphyromonas gingivalis/fisiologia , Coelhos , Espectrofotometria Ultravioleta , Staphylococcus aureus/efeitos dos fármacos , Tinidazol/química , Tinidazol/farmacologia , Fatores de Virulência/antagonistas & inibidores
9.
PLoS One ; 15(8): e0237583, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32804936

RESUMO

Identification and quantification of plant flavonoids are critical to pharmacokinetic study and pharmaceutical quality control due to their distinct pharmacological functions. Here we report on a novel plant flavonoid electrochemical sensor for sensitive and selective detection of dihydromyricetin (DMY) based on double- layered membranes consisting of gold nanoparticles (Au) anchored on reduced graphene oxide (rGO) and molecularly imprinted polymers (MIPs) modified glassy carbon electrode (GCE). Both rGO-Au and MIPs membranes were directly formed on GCE via in-situ electrochemical reduction and polymerization processes step by step. The compositions, morphologies, and electrochemical properties of membranes were investigated with X-ray powder diffractometry (XRD), Fourier transform infrared spectrum (FTIR), Field emission scanning electron microscopy (FESEM) combined with various electrochemical methods. The fabricated electrochemical sensor labeled as GCE│rGO-Au/MIPs exhibited excellent performance in determining of DMY under optimal experimental conditions. A wide linear detection range (LDR) ranges from 2.0×10-8 to 1.0×10-4 M together with a low limit of detection (LOD) of 1.2×10-8 M (S/N = 3) were achieved. Moreover, the electrochemical sensor was employed to determine DMY in real samples with satisfactory results.


Assuntos
Carbono/química , Técnicas Eletroquímicas/instrumentação , Flavonoides/análise , Flavonóis/análise , Grafite/química , Técnicas Biossensoriais/métodos , Eletrodos , Ouro , Limite de Detecção , Nanopartículas Metálicas , Impressão Molecular , Extratos Vegetais/análise , Polímeros/síntese química , Polímeros/química , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios X
10.
J Chromatogr A ; 1626: 461389, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797860

RESUMO

The reliable measurement of very volatile organic compounds (VVOC) in indoor air by use of thermal desorption gas chromatography (TD-GC) in order to include them into evaluation schemes for building products even nowadays is a great challenge. For capturing these small molecules with carbon numbers ranging from C1C6, strong adsorbents are needed. In the present study, recovery rates of nine suitable adsorbents of the groups of porous polymers, graphitised carbon blacks (GCB) and carbon molecular sieves (CMS) are tested against a complex test gas standard containing 29 VVOC. By consideration of the recovery and the relative humidity (50% RH), combinations of the GCB Carbograph 5TD, the two CMS Carboxen 1003 and Carbosieve SII as well as the porous polymer Tenax® GR were identified to be potentially suitable for sampling the majority of the VVOC out of the gas mix. The results reveal a better performance of the adsorbents in combination than being used alone, particularly under humid sampling conditions. The recovery rates of the chosen compounds on each adsorbent should be in the range of 80-120%.


Assuntos
Poluição do Ar em Ambientes Fechados/análise , Cromatografia Gasosa-Espectrometria de Massas/métodos , Compostos Orgânicos Voláteis/análise , Adsorção , Carbono/química , Gases/química , Umidade , Polímeros/química , Temperatura
11.
Nat Commun ; 11(1): 3783, 2020 07 29.
Artigo em Inglês | MEDLINE | ID: mdl-32728021

RESUMO

Current thermochemical methods to generate H2 include gasification and steam reforming of coal and natural gas, in which anthropogenic CO2 emission is inevitable. If biomass is used as a source of H2, the process can be considered carbon-neutral. Seaweeds are among the less studied types of biomass with great potential because they do not require freshwater. Unfortunately, reaction pathways to thermochemically convert salty and wet biomass into H2 are limited. In this study, a catalytic alkaline thermal treatment of brown seaweed is investigated to produce high purity H2 with substantially suppressed CO2 formation making the overall biomass conversion not only carbon-neutral but also potentially carbon-negative. High-purity 69.69 mmol-H2/(dry-ash-free)g-brown seaweed is produced with a conversion as high as 71%. The hydroxide is involved in both H2 production and in situ CO2 capture, while the Ni/ZrO2 catalyst enhanced the secondary H2 formation via steam methane reforming and water-gas shift reactions.


Assuntos
Carbono/isolamento & purificação , Hidrogênio/isolamento & purificação , Energia Renovável , Alga Marinha/química , Álcalis/química , Biomassa , Carbono/química , Catálise , Temperatura Alta , Hidrogênio/química , Vapor
12.
Nat Commun ; 11(1): 3474, 2020 07 10.
Artigo em Inglês | MEDLINE | ID: mdl-32651392

RESUMO

RNase MRP is an essential eukaryotic ribonucleoprotein complex involved in the maturation of rRNA and the regulation of the cell cycle. RNase MRP is related to the ribozyme-based RNase P, but it has evolved to have distinct cellular roles. We report a cryo-EM structure of the S. cerevisiae RNase MRP holoenzyme solved to 3.0 Å. We describe the structure of this 450 kDa complex, interactions between its components, and the organization of its catalytic RNA. We show that some of the RNase MRP proteins shared with RNase P undergo an unexpected RNA-driven remodeling that allows them to bind to divergent RNAs. Further, we reveal how this RNA-driven protein remodeling, acting together with the introduction of new auxiliary elements, results in the functional diversification of RNase MRP and its progenitor, RNase P, and demonstrate structural underpinnings of the acquisition of new functions by catalytic RNPs.


Assuntos
Microscopia Crioeletrônica , Endorribonucleases/ultraestrutura , Ribonucleoproteínas/ultraestrutura , Carbono/química , Catálise , Domínio Catalítico , Humanos , Modelos Moleculares , Conformação de Ácido Nucleico , Conformação Proteica , RNA Catalítico/química , RNA Fúngico/química , Ribonuclease P/química , Saccharomyces cerevisiae/enzimologia
13.
Chemosphere ; 255: 127013, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32679631

RESUMO

In order to obtain higher agricultural yields, the use of chemical substances has been increased to prevent the proliferation of pests, as well as ensuring durability in the storage of the food produced. Such substances are known as pesticides that may well present risks to human health and the environment. In the presence of metal ions, these substances can interact forming new species with different characteristics. Carbendazim (MBC) is an example of a harmful pesticide, which has atoms of nitrogen and oxygen in its structure that can form complexes with metal ions. Thus, in this work has studied the interaction between the copper (II) metal ion and carbendazim and its formation in natural water. The Cu-MBC complex showed a reduction peak of 0.007 V and an oxidation peak of 0.500 V, with characteristics of a quasi-reversible process under a glassy carbon electrode. By anodic stripping voltammetry, a different behavior was observed in the interaction of copper and carbendazim in ultrapure water and Billings dam water; however, it was possible to observe the complex in both samples. Carbendazim in the presence of the metal shows lower oxidation potential value, indicating the influence of the metal on the electrochemical response of the pesticide.


Assuntos
Benzimidazóis/química , Carbamatos/química , Cobre/química , Poluentes Químicos da Água/química , Carbono/química , Técnicas Eletroquímicas/métodos , Eletrodos , Oxirredução
14.
Int J Nanomedicine ; 15: 4139-4149, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32606669

RESUMO

Introduction: A correlation is established between the efficacy of Chinese herbal medicine and its charcoal drugs. Lonicerae japonicae Flos (LJF) is commonly used to treat fever, carbuncle, and tumors, among others. LJF Carbonisatas (LJFC) is preferred for detoxifying and relieving dysentery and its related symptoms. However, the mechanisms underlying the effects of LJFC remain unknown. Aim: The aim of this study was to explore the effects of LJFC-derived carbon dots (LJFC-CDs) on lipopolysaccharide (LPS)-induced fever and hypothermia rat models. Methods: LJFC-CDs were characterized using transmission electron microscopy, high-resolution transmission electron microscopy, Fourier-transform infrared, ultraviolet, fluorescence, X-ray photoelectron spectroscopy, X-ray diffraction and high-performance liquid chromatography. The anti-inflammatory effects of LJFC-CDs were evaluated and confirmed using rat models of LPS-induced fever or hypothermia. Results: The LJFC-CDs ranged from 1.0 to 10.0 nm in diameter, with a yield of 0.5%. LJFC-CDs alleviated LPS-induced inflammation, as demonstrated by the expression of tumor necrosis factor-α, interleukin (IL)-1ß, and IL-6 and the recovery of normal body temperature. Conclusion: LJFC-CDs may have an anti-inflammatory effect and a potential to alleviate fever and hypothermia caused by inflammation.


Assuntos
Carbono/química , Febre/tratamento farmacológico , Hipotermia/tratamento farmacológico , Lonicera/química , Extratos Vegetais/uso terapêutico , Animais , Temperatura Corporal/efeitos dos fármacos , Cromatografia Líquida de Alta Pressão , AMP Cíclico/metabolismo , Citocinas/metabolismo , Dinoprostona/metabolismo , Modelos Animais de Doenças , Medicamentos de Ervas Chinesas/química , Mediadores da Inflamação/sangue , Lipopolissacarídeos , Masculino , Camundongos , Extratos Vegetais/toxicidade , Células RAW 264.7 , Ratos Sprague-Dawley , Espectrometria de Fluorescência
15.
PLoS One ; 15(7): e0235407, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32649670

RESUMO

Fast scan cyclic voltammetry (FSCV) allows for real -time analysis of phasic neurotransmitter levels. Tryptophan (TRP) is an aromatic amino acid responsible for facilitating electron transfer kinetics in oxidoreductase enzymes. Previous work with TRP-modified electrodes showed increased sensitivity for cyclic voltammetry detection of dopamine (DA) when used with slower scan rates (0.05 V/s). Here, we outline an in vitro proof of concept for TRP-modified electrodes in FSCV detection of DA, and decreased sensitivity for ascorbic acid (AA). TRP-modified electrodes had a limit of detection (LOD) for DA of 2.480 ± 0.343 nM compared to 8.348 ± 0.405 nM for an uncoated electrode. Selectivity for DA/ascorbic acid (AA) was 1.107 ± 0.3643 for uncoated and 15.57 ± 4.184 for TRP-modified electrodes. Additionally, these TRP-modified electrodes demonstrated reproducibility when exposed to extended cycling. TRP-modified electrodes will provide an effective modification to increase sensitivity for DA.


Assuntos
Técnicas Biossensoriais , Dopamina/isolamento & purificação , Técnicas Eletroquímicas , Ácido Ascórbico/química , Carbono/química , Dopamina/química , Eletrodos , Cinética , Triptofano/química , Ácido Úrico/química
16.
Food Chem ; 333: 127495, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-32663747

RESUMO

Various pesticides employed in modern agriculture result in large amounts of pesticide residues in agricultural production, greatly threatening human health. Herein, we report a facile approach to fabricate a reduced graphene oxide/cyclodextrin modified glassy carbon electrode (rGO/CD/GCE) for the sensitive electrochemical sensing of imidacloprid (IDP). Three different modified electrodes using CDs (α-, ß-, γ-CD) were fabricated, and their electrochemical performance was further studied. The results demonstrate that α-CD possesses the best signal amplification for IDP. Compared with wet-chemical synthesis of rGO/CDs (W-rGO/CDs), the electrochemical synthesis of rGO/CDs (E-rGO/CDs) produced sensors that showed better performance for IDP sensing. Taking advantage of prepared E-rGO/α-CD nanocomposite, the fabricated sensor offered a low detection limit (0.02 µM) with a wider linear range (0.5-40 µM) and long-term stability. The new sensor was successfully applied for the detection of IDP in brown rice, providing a new technique for efficient and convenient monitoring of pesticide residues in food.


Assuntos
Ciclodextrinas/química , Técnicas Eletroquímicas/métodos , Grafite/química , Inseticidas/análise , Neonicotinoides/análise , Nitrocompostos/análise , Oryza/química , Carbono/química , Técnicas Eletroquímicas/instrumentação , Eletrodos , Contaminação de Alimentos/análise , Nanocompostos/química , Oxirredução , Sementes/química , Sensibilidade e Especificidade
17.
Chemosphere ; 259: 127440, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32590178

RESUMO

A new mixed matrix membrane (MMM) was prepared by incorporating biological mesoporous carbon microspheres (mCMSs) from corn starch polysaccharide-supported hydrophilic polydopamine (PDA), as a mesoporous and large-surface area filler, selective modifier, and pore-forming agent, into polyvinylidene fluoride (PVDF) matrix in presence of polyethylene glycol (PEG) as a hydrophilic agent. The structural parameters of the prepared membranes were characterized via FE-SEM, BET/BJH, XRD, FT-IR, and AFM analyses, sorption experiments, water permeability assessments, porosimetry tests, flux recovery ratio (FRR) evaluations, and contact angle measurements, with the so-called central composite design (CCD) been successfully applied for optimization and investigation of the effects of the operational parameters. The results were then applied to treat double-distilled water containing bovine serum albumin (BSA) utilizing a cross-module set-up. Based on the findings, the content of the mCMS-PDA in the PVDF matrix significantly affected the contact angle, pure water flux (PWF), FRR, and BSA removal. In this respect, the PWF of the PVDF-PEG-mCMS-PDA increased from 10.25 to 27.78 L/m2 h with increasing the mCMS-PDA content, with the peak FRR (93.84%) of the PVDF-PEG-mCMS-PDA seen at maximum surface hydrophilicity of the membrane.


Assuntos
Carbono/química , Membranas Artificiais , Soroalbumina Bovina/química , Purificação da Água/métodos , Interações Hidrofóbicas e Hidrofílicas , Indóis , Microesferas , Permeabilidade , Polímeros , Polivinil , Espectroscopia de Infravermelho com Transformada de Fourier , Água/química , Zea mays
18.
Nat Commun ; 11(1): 3188, 2020 06 24.
Artigo em Inglês | MEDLINE | ID: mdl-32581225

RESUMO

Nitric oxide (NO) has been implicated in a variety of physiological and pathological processes. Monitoring cellular levels of NO requires a sensor to feature adequate sensitivity, transient recording ability and biocompatibility. Herein we report a single-atom catalysts (SACs)-based electrochemical sensor for the detection of NO in live cellular environment. The system employs nickel single atoms anchored on N-doped hollow carbon spheres (Ni SACs/N-C) that act as an excellent catalyst for electrochemical oxidation of NO. Notably, Ni SACs/N-C shows superior electrocatalytic performance to the commonly used Ni based nanomaterials, attributing from the greatly reduced Gibbs free energy that are required for Ni SACs/N-C in activating NO oxidation. Moreover, Ni SACs-based flexible and stretchable sensor shows high biocompatibility and low nanomolar sensitivity, enabling the real-time monitoring of NO release from cells upon drug and stretch stimulation. Our results demonstrate a promising means of using SACs for electrochemical sensing applications.


Assuntos
Técnicas Biossensoriais/métodos , Níquel/química , Óxido Nítrico/análise , Nitrogênio/química , Técnicas Biossensoriais/instrumentação , Carbono/química , Catálise , Eletroquímica , Células Endoteliais da Veia Umbilical Humana/metabolismo , Humanos , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Óxido Nítrico/metabolismo , Oxirredução
19.
PLoS One ; 15(6): e0234148, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32502185

RESUMO

In this paper, Response Surface Methodology with central composite design (RSM/CCD) was used to optimize a modified electrode for improved electron transfer rate and electrochemical performance. The modification was done on a screen-printed carbon electrode (SPCE) with reduced graphene oxide (ERGO)/calix [4] arene (ERGOC4-SPCE). The properties of the modified electrodes were analyzed via cyclic voltammetry, Raman spectroscopy, and Fourier-Transform Infrared (FT-IR) spectroscopy. Then, different variables were optimized, namely, the concentration of graphene oxide, GO (A), the number of scan cycles of graphene oxide (B), and the deposition time (C). The effect of the optimized variables on the reduction-oxidation peak current response of the potassium ferricyanide redox system was analyzed. By using statistical analysis, it shows a significant effect of the concentration of GO, the deposition time, and the number of scans cycles on the peak current response. The coefficient of determination (R2) value of 0.9987 produced indicated a good fit of the model with experimental finding.


Assuntos
Calixarenos/química , Condutividade Elétrica , Grafite/química , Carbono/química , Eletrodos , Oxirredução , Espectroscopia de Infravermelho com Transformada de Fourier , Análise Espectral Raman , Propriedades de Superfície
20.
Food Chem ; 328: 127063, 2020 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-32485582

RESUMO

A magnetic fluorescence probe was fabricated by coating carbon quantum dots-doped molecularly imprinted polymers (MIPs) layers on the surface of Fe3O4 particles (MFMP) for detection of N-acyl homoserine lactones (AHLs) signaling molecules. N-Z-L-homoserine lactone molecular was used as the template to prepare AHLs MIP layers, employing MAA and HEMA as functional monomers. The developed MFMP owned superparamagnetism, fluorescence, fast response and class-selectivity. If AHLs (C4-HSL, C6-HSL, C8-HSL, C10-HSL, C12-HSL and C14-HSL) were captured by the MFMP, they quenched the fluorescence of the probe. Fluorescence dropped linearly in the concentration ranges of 3.65 × 10-3 µmol/L-0.96 × 10-1 µmol/L for AHLs. The MFMP was applied to the analysis of fish juice and milk samples, and recoveries ranged from 83.10% to 90.74% with relative standard deviation less than 5.1%. This study offered a novel strategy to fabricated AHLs fluorescence probe with great potential for wide-ranging application in agri-food products.


Assuntos
Acil-Butirolactonas/análise , Carbono/química , Peixes , Corantes Fluorescentes/química , Leite/química , Impressão Molecular , Pontos Quânticos/química , Animais , Imãs/química , Polímeros/síntese química
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