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1.
Phys Chem Chem Phys ; 21(33): 18352-18362, 2019 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-31402363

RESUMO

Graphene coated gold nanoparticles (GGNPs) have attracted great attention in recent years because of their high thermal stability and unique optical properties. In this paper, we study photothermal properties of GGNPs using the Mie and Gans theories combined with the Pennes bioheat equation. The effect of various sizes and different shapes of GGNPs such as nanosphere, nanorod and nanodisc are taken into account. The extinction efficiency and temperature distribution in tumor tissue show that graphene coated gold nanorods, because of the high temperature rise during laser irradiation, are more suitable candidates for photothermal therapy (PTT) applications. Also, we show that the extinction peak of graphene coated gold nanorods can be adjusted in the biological windows by increasing the graphene shell thickness and/or by changing their aspect ratio. Finally, we investigated the effect of the number of graphene layers upon the temperature rise in the tumor and found that the temperature rise increases with increasing number of graphene layers. Our findings introduce a new class of nanoagents which can be used in PTT applications.


Assuntos
Ouro/química , Grafite/química , Nanopartículas Metálicas/química , Nanotubos/química , Fototerapia/métodos
2.
Analyst ; 144(17): 5261-5270, 2019 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-31364612

RESUMO

In this work, an enrichment approach for the profiling of N-linked glycans was developed by utilizing a highly porous 3D graphene composite fabricated from graphene oxide nanosheets and a phenol-formaldehyde polymer via graphitization and KOH activation. In tailoring the large surface area (ca. 2213 m2 g-1) and 3D-layered mesoporous structure, the 3D graphene composite demonstrated not only high efficiency in glycan enrichment but also the size-exclusion effect against residual protein interference. For a standard protein ovalbumin digest, 26 N-linked glycans were identified with good repeatability, and the detection limit was as low as 0.25 ng µL-1 with the identification of 13 N-linked glycans (S/N > 10). When the mass ratio of the ovalbumin digest to the interfering proteins, i.e., bovine serum albumin and ovalbumin was 1 : 2000 : 2000, 18 N-linked glycans could still be detected with sufficient signal intensities. From a 60 nL minute complex human serum sample, up to 53 N-linked glycans with S/N > 10 were identified after the 3D graphene enrichment, while only 20 N-linked glycans were identified by the porous graphitized carbon material used for comparison. In addition, the application of the 3D graphene composite in profiling the up-regulated and down-regulated N-linked glycans from the real clinical serum samples of ovarian cancer patients confirmed the potential of the 3D graphene composite for analyzing minute and complicated biological samples.


Assuntos
Grafite/química , Nanoestruturas/química , Ovalbumina/química , Polissacarídeos/análise , Albumina Sérica/química , Feminino , Formaldeído/química , Humanos , Neoplasias Ovarianas/sangue , Oxirredução , Fenol/química , Fenóis/química , Polímeros/química , Polissacarídeos/isolamento & purificação , Porosidade , Soro
3.
Analyst ; 144(17): 5284-5291, 2019 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-31372627

RESUMO

5,10,15,20-Tetrakis(4-carboxyl phenyl)porphyrin (Por) modified Co(OH)2 deposited on the surface of GO nanocomposites (Por/Co(OH)2/GO) were prepared and characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and XRD. For the first time, H2TCPP/Co(OH)2/GO is found to have enhanced peroxidase-like activity and catalyze the oxidation of the substrate 3,3,5,5-tetramethylbenzidine (TMB) by hydrogen peroxide (H2O2). Notably, the colorless TMB rapidly transformed into blue oxTMB in just 60 s, which was easily observed visually. The catalytic kinetics of H2TCPP/Co(OH)2/GO is in accord with the Michaelis-Menten equation. The catalytic mechanism of H2TCPP/Co(OH)2/GO nanocomposites is attributed to hydroxyl radicals (˙OH), due to decomposition of H2O2, which is verified by using terephthalic acid as a fluorescent probe. What's more, H2O2 can be detected in a wide linear detection range from 5 to 35 mM with a detection limit of 0.385 mM. Furthermore, based on the excellent peroxidase-like activity of H2TCPP/Co(OH)2/GO, a colorimetric sensor is established to sensitively detect glutathione (GSH) in a linear range from 10 to 300 µM with a low detection limit of 9.5 µM.


Assuntos
Cobalto/química , Grafite/química , Hidróxidos/química , Nanocompostos/química , Peroxidases/química , Porfirinas/química , Benzidinas/química , Materiais Biomiméticos , Técnicas Biossensoriais/métodos , Catálise , Glutationa/análise , Peróxido de Hidrogênio/química , Radical Hidroxila/química , Cinética , Limite de Detecção , Oxirredução , Sensibilidade e Especificidade , Propriedades de Superfície
4.
Analyst ; 144(17): 5108-5116, 2019 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-31373337

RESUMO

We report here the influence of antibody immobilization strategy for protein immunosensors on screen printed carbon electrode arrays in terms of antibody binding activity, analytical sensitivity, limit of detection, and stability. Horseradish peroxidase (HRP) was the model analyte with anti-HRP immobilized on the sensors, and HRP activity was used for detection. Covalently immobilized anti-HRP antibodies on electrodes coated with chitosan, electrochemically reduced graphene oxide (rGO), and dense gold nanoparticle (AuNP) films had only 20-30% of the total immobilized antibodies active for binding. Active antibodies increased to 60% with passively adsorbed antibodies on bare electrodes, to 85% with oriented antibodies using protein A covalently immobilized on AuNP-coated carbon electrode, and to 98% when attached to protein A passively adsorbed onto bare electrodes. Passively adsorbed antibodies on bare electrodes lost activity in 1-2 days, but antibodies immobilized using other strategies remained relatively stable after 5 days. Covalent immobilization gave limits of detection (LOD) of 40 fg mL-1, while passively adsorbed antibodies or protein A on carbon electrodes had LODs 4-8 fg mL-1, but were unstable. Sensitivity was highest for antibodies covalently attached to AuNP electrodes (2.40 nA per log pg per mL) that also had highest antibody coverage, and decreased slightly when protein A on AuNP was used to orient antibodies. Passively adsorbed antibodies and oriented antibodies on protein A gave slightly lower sensitivities. Immobilization strategy or antibody orientation did not have a significant effect on LOD, but dynamic range increased as the number of active antibodies on sensor surfaces increased.


Assuntos
Anticorpos Imobilizados/química , Carbono/química , Técnicas Biossensoriais/métodos , Quitosana/química , Técnicas Eletroquímicas/métodos , Eletrodos , Grafite/química , Peroxidase do Rábano Silvestre/química , Imunoensaio/métodos , Limite de Detecção , Oxirredução , Propriedades de Superfície
5.
J Nanobiotechnology ; 17(1): 83, 2019 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-31291948

RESUMO

BACKGROUND: Macrophages with tumor-tropic migratory properties can serve as a cellular carrier to enhance the efficacy of anti neoplastic agents. However, limited drug loading (DL) and insufficient drug release at the tumor site remain the main obstacles in developing macrophage-based delivery systems. In this study, we constructed a biomimetic delivery system (BDS) by loading doxorubicin (DOX)-loaded reduced graphene oxide (rGO) into a mouse macrophage-like cell line (RAW264.7), hoping that the newly constructed BDS could perfectly combine the tumor-tropic ability of macrophages and the photothermal property of rGO. RESULTS: At the same DOX concentration, the macrophages could absorb more DOX/PEG-BPEI-rGO than free DOX. The tumor-tropic capacity of RAW264.7 cells towards RM-1 mouse prostate cancer cells did not undergo significant change after drug loading in vitro and in vivo. PEG-BPEI-rGO encapsulated in the macrophages could effectively convert the absorbed near-infrared light into heat energy, causing rapid release of DOX. The BDS showed excellent anti-tumor efficacy in vivo. CONCLUSIONS: The BDS that we developed in this study had the following characteristic features: active targeting of tumor cells, stimuli-release triggered by near-infrared laser (NIR), and effective combination of chemotherapy and photothermotherapy. Using the photothermal effect produced by PEG-BPEI-rGO and DOX released from the macrophages upon NIR irradiation, MAs-DOX/PEG-BPEI-rGO exhibited a significant inhibitory effect on tumor growth.


Assuntos
Antineoplásicos/química , Materiais Biomiméticos/química , Portadores de Fármacos/química , Macrófagos/metabolismo , Neoplasias da Próstata/tratamento farmacológico , Animais , Antineoplásicos/administração & dosagem , Linhagem Celular Tumoral , Doxorrubicina/administração & dosagem , Doxorrubicina/química , Liberação Controlada de Fármacos , Grafite/química , Humanos , Hipertermia Induzida , Raios Infravermelhos , Lasers , Masculino , Camundongos Endogâmicos BALB C , Polietilenoglicóis/química , Polietilenoimina/análogos & derivados , Polietilenoimina/química , Distribuição Tecidual
6.
Chem Commun (Camb) ; 55(62): 9104-9107, 2019 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-31298232

RESUMO

We have developed a photoluminescent membrane for microRNA detection, consisting of chemically modified mesoporous silica nanoparticles (CaF2:Yb/Ho@MSNs) attached, via single stranded DNA probes, to flexible polyurethane fibres coated with graphene oxide (GO). By detecting the release of the luminescent nanoparticles resulting from complementary co-hybridization between target miRNA sequences and the DNA probe, accurate measurements of the miRNA concentration at high sensitivity levels can be obtained. The constructs therefore offer a route to rapid detection and the potential for early cancer diagnosis.


Assuntos
Técnicas Biossensoriais , Grafite/química , MicroRNAs/análise , Nanopartículas/química , Dióxido de Silício/química , Tamanho da Partícula , Porosidade , Propriedades de Superfície
7.
J Photochem Photobiol B ; 197: 111530, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31279287

RESUMO

A novel nano-formulations of biocompatible, biodegradable and thermo-responsive graphene quantum dots (GQDs) loaded dextran/poly(N-isopropylacrylamide) (Dex/PNIPAM) copolymeric matrix was synthesized and analyzed the materials characterization, sustained drug delivery system, tissue feasibility in the tissue implantation site. This research report was aimed to grafting and functionalizing thermo-responsive (Dex/PNIPAM) copolymeric composite with presence of graphene quantum dots to achieve thermal responsive drug delivery (TrDD) with no harm effect in the implantation site. The synthesized GQD by using ionic liquid were evaluated by spectroscopic (DLS, PL, XRD and Raman spectroscopy) and Transmission electron microscopic analysis (TEM). The ultra-small GQDs loaded Dex/PNIPAM and was appeared to be asymmetric and open uniform porous structure, which can be significantly favorable for cell uptake and greatly influenced to be an effective drug carrier into the cellular compartment with good fluid flow. The PNIPAM polymeric composite were exhibited sustained and enhanced drug release percentages with increasing temperature at above low critical solution temperature (LCST) is 39 °C comparable to the cumulative drug release profile of below LCST (32 °C), which demonstrated that thermo-responsive polymer was played a significant role in the delivery system. The treated group of GQDs-Dex/PNIPAM was observed that no inflammation and shows noteworthy stromal cell infiltration, demonstrating that the synthesized drug carriers did not harm to the nerves and tissues and only was responsible for the pain management.


Assuntos
Buprenorfina/química , Portadores de Fármacos/química , Grafite/química , Hidrogéis/química , Manejo da Dor , Pontos Quânticos/química , Resinas Acrílicas/química , Animais , Buprenorfina/uso terapêutico , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Dextranos/química , Portadores de Fármacos/farmacologia , Feminino , Corantes Fluorescentes/química , Glicóis/química , Hidrogéis/farmacologia , Camundongos , Músculo Esquelético/patologia , Dor/tratamento farmacológico , Ratos , Ratos Sprague-Dawley
8.
J Environ Sci (China) ; 84: 1-12, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31284901

RESUMO

A series of functional organic-metal AgCl-decorated graphitic carbon nitride (AgCl-CNx) composites were synthesized and applied for the degradation of oxalic acid (OA) under visible light. The highest photocatalytic activity was achieved with AgCl decoration ratio of 1.0 (denoted as AgCl-CN1.0). The pseudo-first-order constant for OA degradation was 0.0722 min-1 with the mineralization efficiency of 90.80% after 60 min reaction in the photocatalytic process with AgCl-CN1.0. A variety of characterization techniques including Brunauer-Emmett-Teller, X-ray diffraction, scanning electron microscope, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectra, ultraviolet-visible diffuse reflectance spectra, photoluminescence, and Mott-Schottky were utilized to elucidate the physicochemical, microstructure, and optical properties contributing to the improvement of the photocatalytic performance. The results showed that AgCl-CN1.0 had an oblate flaky erythrocyte-like structure with a moderate band gap energy of ~3.00 eV. In addition, the effects of the key parameters (i.e., AgCl-CN1.0 dosage, initial OA concentration, solution pH, and presence of natural organic matter) on OA degradation were systematically investigated. Radical scavenger experiments indicated that photogenerated holes, electrons, superoxide anion radicals, and hydroxyl radicals were the dominant reactive species. Moreover, AgCl-CN1.0 exhibited excellent stability and reusability for OA degradation without detectable Ag+ release in the solution over multiple reaction cycles. The efficient OA mineralization could be mainly ascribed to the moderate specific surface area, increased numbers of active sites, and effective interfacial charge transfer of AgCl-CN1.0. Overall, the AgCl-CN1.0 composite was demonstrated to be a highly efficient, stable, and recoverable photocatalyst.


Assuntos
Grafite/química , Compostos de Nitrogênio/química , Ácido Oxálico/química , Fotólise , Compostos de Prata/química , Poluentes Químicos da Água/química
9.
Analyst ; 144(16): 4858-4864, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31294738

RESUMO

An enzyme-free electrochemical aptasensing platform based on a graphene oxide nanosheet-modified gold-disk electrode was developed for the voltammetric detection of alpha-fetoprotein (AFP) in hepatocellular carcinoma by using a Prussian blue nanoparticle (PBNP)-labeled aptamer. The electroactive PBNP, a typical signal-generation tag, was utilized for the labeling of the aminated AFP aptamer by using covalent conjugation. The electrochemical sensing platform was prepared in a simple manner on the basis of a π-π stacking reaction between the immobilized graphene oxide and the PBNP-labeled AFP aptamer. Upon target AFP introduction, the analyte reacted with the aptamer, thus resulting in the dissociation of the PBNP from the nanosheets. In the presence of DNase I, the newly formed AFP/aptamer-PBNP complex was cleaved to release target AFP, which could react again with the aptamer on the nanosheets, thereby causing target recycling. During this process, the cleaved PBNP-aptamer was far away from the electrode to decrease the voltammetric signal. Under optimum conditions, the voltammetric peak current of the modified electrode decreased with the increment of the target AFP concentration within the linear range of 0.01-300 ng mL-1 at a low detection limit of 6.3 pg mL-1. The precision and reproducibility of the aptasensing protocol were acceptable (CV: <15% for intra-assay and inter-assay). Other possible nontarget biomarkers did not interfere significantly with the voltammetric signal of this system. Human serum samples containing target AFP were assayed with electrochemical aptasensing and a commercial human AFP ELISA kit, and gave well-matched results from these two methods. Importantly, our strategy provides a new horizon for the determination of disease-related proteins.


Assuntos
Carcinoma Hepatocelular/diagnóstico , Ferrocianetos/química , Grafite/química , Neoplasias Hepáticas/diagnóstico , Nanopartículas/química , alfa-Fetoproteínas/análise , Técnicas Biossensoriais , Carcinoma Hepatocelular/química , Técnicas Eletroquímicas , Eletrodos , Ouro/química , Humanos , Limite de Detecção , Neoplasias Hepáticas/química , Sensibilidade e Especificidade
10.
Int J Nanomedicine ; 14: 4833-4847, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31308661

RESUMO

Background: The use of functionalized graphene oxide (fGO) has led to a new trend in the sensor field, owing to its high sensitivity with regards to sensing characteristics and easy synthesis procedures. Methods: In this study, we developed an ultra-sensitive carboxyl-graphene oxide (carboxyl-GO)-based surface plasmon resonance (SPR) aptasensor using peptides to detect human chorionic gonadotropin (hCG) in clinical serum samples. The carboxyl-GO based SPR aptasensor provided high affinity and stronger binding of peptides, which are great importance to allow for a non-immunological label-free mechanism. Also, it allows the detection of low concentrations of hCG, which are in turn considered to be important clinical parameters to diagnose ectopic pregnancies and paraneoplastic syndromes. Results: The high selectivity of the carboxyl-GO-based SPR aptasensor for hCG recombinant protein was verified by the addition of the interfering proteins bovine serum albumin (BSA) and human serum albumin (HSA), which did not affect the sensitivity of the sensor. The carboxyl-GO-based chip can enhance the assay efficacy of interactions between peptides and had a high affinity binding for a ka of 17×106 M-1S-1. The limit of detection for hCG in clinical serum samples was 1.15 pg/mL. Conclusion: The results of this study demonstrated that the carboxyl-GO-based SPR aptasensor had excellent sensitivity, affinity and selectivity, and thus the potential to be used as disease-related biomarker assay to allow for an early diagnosis, and possibly a new area in the field of biochemical sensing technology.


Assuntos
Técnicas Biossensoriais/instrumentação , Gonadotropina Coriônica/sangue , Grafite/química , Ressonância de Plasmônio de Superfície/instrumentação , Animais , Bovinos , Eletroquímica , Humanos , Peptídeos/química , Espectroscopia Fotoeletrônica , Soroalbumina Bovina/química
11.
Anal Chim Acta ; 1074: 80-88, 2019 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-31159942

RESUMO

A rapid and sensitive electrochemical biosensor was constructed to detect Salmonella using invA gene biosensor. The biosensing was based on polyrrole-reduced graphene oxide (PPy-rGO) nanocomposite modified glassy carbon electrode (GCE) and signal amplification with horseradish peroxidase-streptavidin biofunctionalized gold nanoparticles (AuNPs-HRP-SA). PPy-rGO was prepared at 60 °C by chemical reduction of PPy-functionalized graphene oxide (PPy-GO) that was synthesized by in situ polymerization at room temperature. The detection signal was amplified via enzymatic reduction of H2O2 in the presence of hydroquinone (HQ) using AuNPs-HRP-SA as nanotag. Under optimal conditions, the differential pulse voltametric (DPV) signal from the biosensor was linearly related to the logarithm of target invA gene concentrations from 1.0 × 10-16 to 1.0 × 10-10 M, and the limit of detection (LOD) was 4.7 × 10-17 M. The biosensor can also detect Salmonella in the range of 9.6 to 9.6 × 104 CFU mL-1, with LOD of 8.07 CFU mL-1. The biosensor showed good regeneration ability, acceptable selectivity, repeatability and stability, which bode well as an alternative method for Salmonella screening.


Assuntos
Proteínas de Bactérias/genética , Técnicas de Tipagem Bacteriana/métodos , Grafite/química , Nanopartículas Metálicas/química , Polímeros/química , Pirróis/química , Salmonella/isolamento & purificação , Técnicas Biossensoriais/métodos , Carbono , DNA Bacteriano/genética , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Enzimas Imobilizadas/química , Ouro/química , Peroxidase do Rábano Silvestre/química , Peróxido de Hidrogênio/química , Hidroquinonas/química , Limite de Detecção , Nanocompostos/química , Hibridização de Ácido Nucleico , Oxirredução , Salmonella/genética , Estreptavidina/química
12.
Chemosphere ; 233: 9-16, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31163310

RESUMO

The effects of cadmium (Cd) on wheat seedlings in the presence of graphene oxide (GO) were investigated. Parameters evaluated include root morphology, microtubule protein content, cytochrome P450 activity, and the microcellular structure of wheat seedlings. Compared with treatments with Cd or GO in isolation, treatments combining GO and Cd inhibited the total root length, total root surface area, average root diameter, and number of root hairs. GO combined with Cd also increased cytochrome P450 activity and reduced tubulin content. Cotransport of GO-loading Cd entered root tissues and was then transported to the mesophyll cells; this, in turn, triggered damage to cellular structures, including the cell membranes and chloroplast, leading to root blockage and reduced respiratory efficiency, decreased effectiveness of water and nutrient absorption, and ultimate inhibition of wheat growth and development. These effects of GO exposure were also concentration-dependent. The results indicated that GO amplified the phytotoxicity of Cd in wheat seedling roots. Given the worldwide exposure of the environment to Cd contamination, careful consideration should be given to the effects of GO in combination with Cd in agricultural management.


Assuntos
Cádmio/toxicidade , Grafite/química , Poluentes do Solo/toxicidade , Triticum/efeitos dos fármacos , Cádmio/química , Compostos de Cádmio , Óxidos/química , Raízes de Plantas/metabolismo , Plântula/efeitos dos fármacos , Poluentes do Solo/química , Triticum/metabolismo
13.
Analyst ; 144(13): 3999-4005, 2019 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-31172144

RESUMO

Micrococcal nuclease (MNase) is an extracellular endonuclease of Staphylococcus aureus (S. aureus). It digests single stranded nucleic acid. The presence of MNase is the gold standard to identify S. aureus and its content. The present study reports the ultrahigh sensitive and selective fluorescence platform for MNase detection, designed and developed based on the surface energy transfer mechanism. A "proof of concept" is being developed based on monoclonal antibody-conjugated quantum dots (mAb-QDs), wherein mAb-QDs act as donors and graphene oxide (GO) acts as an acceptor. mAb-QDs in close proximity to GO undergo adsorption due to weak affinity between them and this results in fluorescence quenching by the transfer of surface energy from mAb-QDs to GO. During sensing, a much stronger affinity of mAb-QDs towards MNase inhibits the energy transfer to GO and this allows the regaining of fluorescence. Immobilized mAb-QDs on nitrocellulose membrane strips were fabricated and tested for "ON-OFF-ON" sensing of MNase. The limit of detection for fluorescence based assay and strips is found to be 0.3 ng mL-1 and 0.5 ng mL-1, respectively. The developed strips were applied on real samples for the detection of S. aureus.


Assuntos
Corantes Fluorescentes/química , Grafite/química , Nuclease do Micrococo/análise , Pontos Quânticos/química , Staphylococcus aureus/química , Anticorpos Monoclonais/química , Técnicas Biossensoriais/métodos , Colódio/química , Transferência Ressonante de Energia de Fluorescência/métodos , Limite de Detecção , Membranas Artificiais , Nanocompostos , Estudo de Prova de Conceito , Sensibilidade e Especificidade , Staphylococcus aureus/enzimologia
14.
Anal Chim Acta ; 1073: 22-29, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31146832

RESUMO

An electrochemical sensor based on a glassy carbon electrode (GCE) modified by three-dimensional graphene (3D-GE) and polyglutamic acid (PGA) was developed to quantitatively detect Amoxicillin (AMX), a worldwide used antibiotic. AMX response at PGA/3D-GE/GCE involving the transfer of one electron and an equal number of protons were determined using electrochemical approaches. Density functional theory simulations were performed to give insights on the reaction mechanism of AMX on the surface of the modified electrode. When the optimization of the experimental conditions was completed, the linear range of AMX was 2-60 µM. Besides, the detection limit was calculated as 0.118 µM (S/N = 3). And the modified electrode could detect the concentration of the AMX in human urine samples. Overall, the developed PGA/3D-GE/GCE for determination of AMX shows great potentials in practice.


Assuntos
Amoxicilina/química , Teoria da Densidade Funcional , Grafite/química , Simulação de Dinâmica Molecular , Ácido Poliglutâmico/química , Técnicas Eletroquímicas , Eletrodos , Tamanho da Partícula , Propriedades de Superfície
15.
Anal Chim Acta ; 1072: 25-34, 2019 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-31146862

RESUMO

For the first time, a simple electrochemical co-deposition was utilized to synthesis the gold and zirconia nanocomposites modified graphene nanosheets on glassy carbon electrode (Au-ZrO2-GNs/GCE) for electrocatalytic analysis of methyl parathion (MP). According to Field-Emission Scanning Electron Microscopy (FE-SEM), Transmission Electronic Microscopy (TEM) and X-Ray Diffraction (XRD), the gold nanoparticles were uniformly distributed on the surface of graphene-based nanocomposite. The Au-ZrO2-GNs/GCE based sensor exhibited superior capacity for MP detection, ascribed to the strong affinity of zirconia towards the phosphoric group, as well as the high catalytic activity and good conductivity of Au-GNs. The best fabrication and work conditions were then obtained by systematically optimization of the electrodeposition process, pH value and enrichment time. Compared to the gold nanoparticles, zirconia or graphene modified electrodes, AuZrO2-GNs/GCE sensor displayed superior electro-catalytic response toward MP oxidation. The sensor response current of square wave voltammetry was highly linearly correlated with the MP concentrations range of 1-100 ng mL-1 and 100-2400 ng mL-1 with the detection limit of 1 ng mL-1. The Au-ZrO2-GNs/GCE nanocomposite sensor showed excellent accuracy and reproducibility for detection of MP in Chinese cabbage samples, providing a new method for efficient pesticide detection in practical applications.


Assuntos
Técnicas Eletroquímicas , Ouro/química , Grafite/química , Metil Paration/análise , Nanocompostos/química , Zircônio/química , Eletrodos , Tamanho da Partícula , Propriedades de Superfície
16.
Anal Chim Acta ; 1072: 46-53, 2019 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-31146864

RESUMO

In clinical practice, the excess concentration of bilirubin can trigger diseases such as neonatal jaundice, hepatic failure, septicemia, and so on. The concentration of bilirubin is one of important clinical indexes to evaluate patients with hepatic function disease in clinical practice. Therefore, it is very necessary to develop a rapid detection technique detecting the bilirubin in body fluids. Here, a new electrochemical sensor based on Au nanoparticles/tetrathiafulvalene-carboxylate functionalized reduced grapheneoxide 0D-2D heterojunction(AuNPs/TTF-COOH/RGO) was fabricated for the discrimination of bilirubin in real human blood. The TTF-COOH could effectively repair electron conductivity of RGO nanosheets, decrease interface resistance, and also enhance the dispersity of TTF-COOH/RGO nanosheets in water. What's more, the S atoms of TTF-COOH can bonding the gold nano-particles (AuNPs) to fabricate a 0D-2D heterojunction with excellent biocompatibility and enhanced specific surface area. After bilirubin oxidases were self-assembled on the surface of AuNPs, a specific recognition interface was formed as a sensor for the detection of bilirubin. The heterojunction showed enhanced interface electron transfer rate, excellent biocompatibility, and also prominent electrocatalytic activity for the high efficiency catalysis of bilirubin. The sensor shows a linear response for bilirubin from 2.66 to 83  µmol L-1 and a low detection limit of 0.74 µmol L-1 at 3σ. This work provides one novel approach to detection of bilirubin by functional RGO nanosheets, and broadens the application area of RGO nanosheets in selective catalysis and detection of biomolecule in biological specimens, such as blood, urine.


Assuntos
Bilirrubina/sangue , Ácidos Carboxílicos/química , Técnicas Eletroquímicas , Ouro/química , Grafite/química , Compostos Heterocíclicos/química , Nanopartículas Metálicas/química , Eletrodos , Humanos , Prata/química
17.
Bioelectrochemistry ; 129: 189-198, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31195330

RESUMO

A facile approach was reported to synthesize ß-cyclodextrin functionalized graphene that is bridged by 3,4,9,10-perylene tetracarboxylic acid (rGO-PTCA-CD) via a chemical route that involves the functionalization of rGO with PTCA followed by covalently cross-linking NH2-ß-CD. The as-prepared rGO-PTCA-CD was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical methods. The working electrodes were thoroughly studied for the cyclic voltammetry by using [Fe(CN)6]4-/3- as redox probe and using ferrocene as an internal standard. Furthermore, rGO-PTCA-CD was successfully applied to the recognition of phenylalanine enantiomers. The host-guest inclusion interaction between rGO-PTCA-CD and the phenylalanine enantiomers was investigated by differential pulse voltammetry with Fc used as a competitor. The recognition result showed that the rGO-PTCA-CD-modified glassy carbon electrode exhibited higher chiral recognition capability for L-Phe than for D-Phe with an enantioselectivity coefficient of 2.07. The proposed modified electrode had a limit of detection of 0.08 nM and 0.2 nM (S/N = 3) for L-Phe and D-Phe, respectively, with a linear response range of 0.01 mM to 5 mM, which was ascribed to the synergy of the rGO-PTCA (e.g., its excellent electrochemical performance) and ß-CD (e.g., the hydrophobic inner cavity with good molecular recognition and enrichment abilities).


Assuntos
Técnicas Eletroquímicas/métodos , Grafite/química , Perileno/química , Fenilalanina/análise , beta-Ciclodextrinas/química , Eletrodos , Limite de Detecção , Estereoisomerismo
18.
Bioelectrochemistry ; 129: 199-205, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31200249

RESUMO

The identification of plant species not only is a hobby but also has important application value in plant resources science. Traditional plant identification often relies on the experience of botanists. The infrageneric identification of plants is easily mistaken due to similarities in organ features. In this work, we propose an electrochemical method to obtain fingerprints of plant petal tissue. Fourteen species of Lycoris were used as a model for validating this methodology. Pattern and color recognition were established for visualization of electrochemical fingerprints recorded after various solvent extractions. In addition, the infrageneric relationships of these Lycoris species were deduced from the electrochemical fingerprints since the type and content of electroactive compounds in plants are controlled by genes. The results indicate that the electrochemical fingerprints of Lycoris petals are correlated with the infrageneric relationships of native Lycoris species.


Assuntos
Técnicas Eletroquímicas/métodos , Flores/classificação , Lycoris/classificação , Adsorção , Flores/química , Grafite/química , Lycoris/química , Extratos Vegetais/química , Extratos Vegetais/classificação , Solventes , Especificidade da Espécie
19.
Bioelectrochemistry ; 129: 259-269, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31247532

RESUMO

Proton-conducting porous ceramic membranes were synthesized via a polymer-derived ceramic route and probed in a microbial fuel cell (MFC). Their chemical compositions were altered by adding carbon allotropes including graphene oxide (GO) and multiwall carbon nanotubes into a polysiloxane matrix as filler materials. Physical characteristics of the synthesized membranes such as porosity, hydrophilicity, mechanical stability, ion exchange capacity, and oxygen mass transfer coefficient were determined to investigate the best membrane material for further testing in MFCs. The ion exchange capacity of the membrane increased drastically after adding 0.5 wt% of GO at an increment of 9 fold with respect to that of the non-modified ceramic membrane, while the oxygen mass transfer coefficient of the membrane decreased by 52.6%. The MFC operated with this membrane exhibited a maximum power density of 7.23 W m-3 with a coulombic efficiency of 28.8%, which was significantly higher than the value obtained using polymeric Nafion membrane. Hence, out of all membranes tested in this study the GO-modified polysiloxane based ceramic membranes are found to have a potential to replace Nafion membranes in pilot scale MFCs.


Assuntos
Fontes de Energia Bioelétrica , Cerâmica/química , Grafite/química , Membranas Artificiais , Nanotubos de Carbono/química , Siloxanas/química , Fontes de Energia Bioelétrica/microbiologia , Eletricidade , Modelos Moleculares , Porosidade
20.
Environ Pollut ; 251: 945-951, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31234261

RESUMO

The removals of arsenic and selenium pollutants are always urgent desires for the water security. In this study, both sorption and catalysis strategies were combined for the effective removals of As(V) and Se(VI) over magnetic graphene oxide sheets (GOs)-oxidized carbon nanotubes (OCNTs) hydrogels. The sorption behavior facilitated the operation of catalysis reactions, meanwhile, the catalytic reduction promoted the release of occupied sorption sites and then restarted a new sorption-catalysis cycle. The synergic effect of sorption and catalysis realized 258.2 mg g-1 for As(V) enrichment capacity on MPG2T1, and ultra-fast sorption and catalysis equilibriums were identified within 9 min. In the case of Se(VI), a moderate enrichment performance was observed to be 46.2 mg g-1. Similarly, the ultra-fast sorption and reduction of Se(VI) were realized within 2 min. In the competition experiments, only SO42-, SO32-, and HPO42- showed interference for As(V) and Se(VI) removals. These results testified the superiority of the synergy effect of sorption and catalysis, and the feasibility of 3D magnetic GOs-OCNTs hydrogel in practical implementations.


Assuntos
Arsênico/química , Grafite/química , Nanotubos de Carbono/química , Selênio/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Catálise , Hidrogéis/química
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