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1.
Nat Commun ; 11(1): 4087, 2020 08 14.
Artigo em Inglês | MEDLINE | ID: mdl-32796822

RESUMO

By electronically wiring-up living cells with abiotic conductive surfaces, bioelectrochemical systems (BES) harvest energy and synthesize electric-/solar-chemicals with unmatched thermodynamic efficiency. However, the establishment of an efficient electronic interface between living cells and abiotic surfaces is hindered due to the requirement of extremely close contact and high interfacial area, which is quite challenging for cell and material engineering. Herein, we propose a new concept of a single cell electron collector, which is in-situ built with an interconnected intact conductive layer on and cross the individual cell membrane. The single cell electron collector forms intimate contact with the cellular electron transfer machinery and maximizes the interfacial area, achieving record-high interfacial electron transfer efficiency and BES performance. Thus, this single cell electron collector provides a superior tool to wire living cells with abiotic surfaces at the single-cell level and adds new dimensions for abiotic/biotic interface engineering.


Assuntos
Eletroquímica/métodos , Biofilmes/crescimento & desenvolvimento , Catálise , Eletrodos , Microscopia Eletroquímica de Varredura , Microscopia Eletrônica de Transmissão , Shewanella/metabolismo , Shewanella/ultraestrutura
2.
Nat Commun ; 11(1): 3628, 2020 07 20.
Artigo em Inglês | MEDLINE | ID: mdl-32686668

RESUMO

Triazolopyridinone derivatives are of high value in both medicinal and material chemistry. However, the chiral or hindered triazolopyridinone derivatives remain an underexplored area of chemical space because they are difficult to prepare via conventional methods. Here we report an electrochemical rearrangement for the efficient synthesis of otherwise inaccessible triazolopyridinones with diverse alkyl carboxylic acids as starting materials. This enables the efficient preparation of more than 60 functionalized triazolopyridinones under mild conditions in a sustainable manner. This method is evaluated for the late stage modification of bioactive natural products, amino acids and pharmaceuticals, and it is further applied to the decagram scale preparation of enantiopure triazolopyridinones. The control experiments support a mechanism involving an oxidative cyclization and 1,2-carbon migration. This facile and scalable rearrangement demonstrates the power of electrochemical synthesis to access otherwise-inaccessible triazolopyridinones and may find wide application in organic, material and medicinal chemistry.


Assuntos
Purinas/síntese química , Química Farmacêutica/métodos , Eletroquímica/métodos , Purinas/análise
3.
J Vis Exp ; (158)2020 04 23.
Artigo em Inglês | MEDLINE | ID: mdl-32420985

RESUMO

Phasic dopamine (DA) release from the ventral tegmental area (VTA) to the nucleus accumbens plays a pivotal role in reward processing and reinforcement learning. Understanding how the diverse neuronal inputs into the VTA control phasic DA release can provide a better picture of the circuitry that controls reward processing and reinforcement learning. Here, we describe a method that combines intra-VTA cannula infusions of pharmacological agonists and antagonists with stimulation-evoked phasic DA release (combined infusion and stimulation, or CIS) as measured by in vivo fast-scan cyclic voltammetry (FSCV). Using CIS-FSCV in anesthetized rats, a phasic DA response can be evoked by electrically stimulating the VTA with a bipolar electrode fitted with a cannula while recording in the nucleus accumbens core. Pharmacological agonists or antagonists can be infused directly at the stimulation site to investigate specific VTA receptors' roles in driving phasic DA release. A major benefit of CIS-FSCV is that VTA receptor function can be studied in vivo, building on in vitro studies.


Assuntos
Dopamina/metabolismo , Eletroquímica/métodos , Receptores de Superfície Celular/metabolismo , Área Tegmentar Ventral/metabolismo , Animais , Masculino , Ratos , Recompensa
4.
Nat Commun ; 11(1): 2668, 2020 05 29.
Artigo em Inglês | MEDLINE | ID: mdl-32472057

RESUMO

Electrochemiluminescence (ECL) is a powerful transduction technique with a leading role in the biosensing field due to its high sensitivity and low background signal. Although the intrinsic analytical strength of ECL depends critically on the overall efficiency of the mechanisms of its generation, studies aimed at enhancing the ECL signal have mostly focused on the investigation of materials, either luminophores or coreactants, while fundamental mechanistic studies are relatively scarce. Here, we discover an unexpected but highly efficient mechanistic path for ECL generation close to the electrode surface (signal enhancement, 128%) using an innovative combination of ECL imaging techniques and electrochemical mapping of radical generation. Our findings, which are also supported by quantum chemical calculations and spin trapping methods, led to the identification of a family of alternative branched amine coreactants, which raises the analytical strength of ECL well beyond that of present state-of-the-art immunoassays, thus creating potential ECL applications in ultrasensitive bioanalysis.


Assuntos
Biomarcadores/análise , Técnicas Biossensoriais/métodos , Técnicas Eletroquímicas/métodos , Eletroquímica/métodos , Medições Luminescentes/métodos , Técnicas de Química Analítica , Físico-Química/métodos , Luminescência
5.
J Environ Sci Health B ; 55(6): 583-591, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32238102

RESUMO

An original voltammetric screening method, employing glassy carbon electrode (GCE) with the differential-pulse voltammetry technique (DPV), has been developed to determine residues of the anti-parasitic agent Ronidazole (RNZ) in bovine meat. By using cyclic voltammetry (CV), it has been demonstrated that an irreversible cathodic process occurs at approximately -0.740 V (vs. Ag|AgCl, KCl 3 mol L-1) in a 0.100 mol L-1 phosphate buffer at pH 6.5 as supporting electrolyte. Furthermore, the behavior of RNZ in CV indicates the occurrence of a diffusion mass transfer process to the working electrode surface. The RNZ reduction mechanism was proposed as a 6-electron transfer, similar to Metronidazole under the same pH range. Quantification of RNZ and method validation were then carried out by DPV. The relative standard deviation (RSD) were 3.21% for intraday precision of 10 consecutive repetitions and 6.78% for interday precision after five analysis. Limits of detection and quantification were also obtained, and the values were 0.107 and 0.358 mg kg-1, respectively. The recovery percentage for three different concentrations of RNZ in the bovine meat matrix ranged between 98.1% and 100.3%. The method proved to be efficient for screening RNZ in bovine meat.


Assuntos
Eletroquímica/métodos , Análise de Alimentos/métodos , Carne Vermelha/análise , Ronidazole/análise , Animais , Carbono , Bovinos , Eletroquímica/instrumentação , Eletrodos , Análise de Alimentos/instrumentação , Contaminação de Alimentos/análise , Limite de Detecção , Reprodutibilidade dos Testes
6.
Nat Commun ; 11(1): 1505, 2020 03 20.
Artigo em Inglês | MEDLINE | ID: mdl-32198474

RESUMO

Root nodules are agricultural-important symbiotic plant-microbe composites in which microorganisms receive energy from plants and reduce dinitrogen (N2) into fertilizers. Mimicking root nodules using artificial devices can enable renewable energy-driven fertilizer production. This task is challenging due to the necessity of a microscopic dioxygen (O2) concentration gradient, which reconciles anaerobic N2 fixation with O2-rich atmosphere. Here we report our designed electricity-powered biological|inorganic hybrid system that possesses the function of root nodules. We construct silicon-based microwire array electrodes and replicate the O2 gradient of root nodules in the array. The wire array compatibly accommodates N2-fixing symbiotic bacteria, which receive energy and reducing equivalents from inorganic catalysts on microwires, and fix N2 in the air into biomass and free ammonia. A N2 reduction rate up to 6.5 mg N2 per gram dry biomass per hour is observed in the device, about two orders of magnitude higher than the natural counterparts.


Assuntos
Eletricidade , Eletroquímica/métodos , Nódulos Radiculares de Plantas/fisiologia , Amônia , Biomassa , Fertilizantes , Modelos Teóricos , Nitrogênio/metabolismo , Ciclo do Nitrogênio , Fixação de Nitrogênio , Simbiose
7.
Sensors (Basel) ; 20(4)2020 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-32093345

RESUMO

Carbon fiber-microelectrodes (CFMEs) have been the standard for neurotransmitter detection for over forty years. However, in recent years, there have been many advances of utilizing alternative nanomaterials for neurotransmitter detection with fast scan cyclic voltammetry (FSCV). Recently, carbon nanotube (CNT) yarns have been developed as the working electrode materials for neurotransmitter sensing capabilities with fast scan cyclic voltammetry. Carbon nanotubes are ideal for neurotransmitter detection because they have higher aspect ratios enabling monoamine adsorption and lower limits of detection, faster electron transfer kinetics, and a resistance to surface fouling. Several methods to modify CFMEs with CNTs have resulted in increases in sensitivity, but have also increased noise and led to irreproducible results. In this study, we utilize commercially available CNT-yarns to make microelectrodes as enhanced neurotransmitter sensors for neurotransmitters such as serotonin. CNT-yarn microelectrodes have significantly higher sensitivities (peak oxidative currents of the cyclic voltammograms) than CFMEs and faster electron transfer kinetics as measured by peak separation (ΔEP) values. Moreover, both serotonin and dopamine are adsorption controlled to the surface of the electrode as measured by scan rate and concentration experiments. CNT yarn microelectrodes also resisted surface fouling of serotonin onto the surface of the electrode over thirty minutes and had a wave application frequency independent response to sensitivity at the surface of the electrode.


Assuntos
Eletroquímica/métodos , Nanotubos de Carbono/química , Serotonina/química , Microeletrodos
8.
Philos Trans A Math Phys Eng Sci ; 378(2167): 20190450, 2020 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-32008445

RESUMO

Here, a bioinspired strategy is used to prepare well-ordered nanotubular structures, as observed in animals and plants, such as gecko toe pads or corals. The nanotubes are obtained by templateless electropolymerization of thieno[3,4-b]thiophene-based monomers with various aromatic groups in an organic solvent (dichloromethane). The most interesting and robust structures were obtained with carbazole and pyrene substituents to the base monomer structure, since these groups participate significantly in the polymerization and also have strong π-stacking interactions. The addition of water to electropolymerization solvent significantly impacted the formation of nanotubes, as it caused the release of a significant amount of H2 and O2 bubbles, depending on the electropolymerization method. Identifying templateless approaches to vary nanotubular structures is very interesting, as these materials are sought-after for applications in water harvesting systems. This article is part of the theme issue 'Bioinspired materials and surfaces for green science and technology (part 3)'.


Assuntos
Eletroquímica/métodos , Cloreto de Metila/química , Nanotecnologia/métodos , Nanotubos/química , Tiofenos/química , Biomimética , Carbazóis/química , Química Verde , Hidrogênio/química , Substâncias Macromoleculares , Microscopia Eletrônica de Varredura , Compostos Orgânicos , Oxigênio/química , Polímeros/química , Solventes/química , Propriedades de Superfície , Água/química , Molhabilidade
9.
J Vis Exp ; (156)2020 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-32091002

RESUMO

Low-grade heat is abundantly available in the environment as waste heat. The efficient conversion of low-grade heat into electricity is very difficult. We developed an asymmetric thermoelectrochemical cell (aTEC) for heat-to-electricity conversion under isothermal operation in the charging and discharging processes without exploiting the thermal gradient or the thermal cycle. The aTEC is composed of a graphene oxide (GO) cathode, a polyaniline (PANI) anode, and 1M KCl as the electrolyte. The cell generates a voltage due to the pseudocapacitive reaction of GO when heating from room temperature (RT) to a high temperature (TH, ~40-90 °C), and then current is successively produced by oxidizing PANI when an external electrical load is connected. The aTEC demonstrates a remarkable temperature coefficient of 4.1 mV/K and a high heat-to-electricity conversion efficiency of 3.32%, working at a TH = 70 °C with a Carnot efficiency of 25.3%, unveiling a new promising thermoelectrochemical technology for low-grade heat recovery.


Assuntos
Eletroquímica/métodos , Temperatura Alta , Compostos de Anilina/química , Eletricidade , Eletrodos , Eletrólitos/química , Grafite/química
10.
Mikrochim Acta ; 187(3): 155, 2020 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-32025820

RESUMO

An electrochemiluminescence (ECL) biosensor was fabricated for the evaluation of prostate specific antigen (PSA). The sensor was developed by successively modifying glassy carbon electrode (GCE) electrodes with CdS/Chito/g-C3N4 nanocomposites and DNA1 was labeled at the 5' end with thiol. The aptamer DNA was labeled at the 3' end with a quencher ferrocene (Fc) was ligated to DNA1 by the principle of complementary base pairing. In the absence of PSA, the ECL intensity signal is effectively quenches through the energy transfer and photoexcitation electron transfer between CdS/Chito/g-C3N4 emitter and quencher Fc. After incubation with target PSA, the aptamer DNA interacts with PSA and then moved away from the electrode surface together, which will recover the ECL intensity. Under the optimal conditions, the ECL intensity increases linearly with the logarithm of PSA concentration in the range of 1 pg·mL-1 to 100 ng·mL-1, and the detection limit is 0.14 pg·mL-1 (S/N = 3). The biosensor has been successfully applied to the determination of PSA in serum sample. Graphical abstractSchematic representation of the electrochemiluminescence sensor based on a CdS/chitosan/g-C3N4 nanocomposite, which can be applied to the determination of prostate specific antigen in serum.


Assuntos
Quitosana/química , Eletroquímica/métodos , Imunoensaio/métodos , Medições Luminescentes/métodos , Nanocompostos/química , Antígeno Prostático Específico/sangue , Humanos
11.
Nat Commun ; 11(1): 192, 2020 01 10.
Artigo em Inglês | MEDLINE | ID: mdl-31924791

RESUMO

Epithelial-mesenchymal transition (EMT) is critically involved in a variety of biological processes. Electrochemical sensing offers potential to develop more effective technology for EMT detection. In this study, by using the unique performance of quantum dot (QD)-nanocomposite materials, we establish an electrochemical biosensor that can specifically detect the change of E-cadherin and analyze different stages of EMT. The signal for EMT is largely magnified due to the transmission of molecular information to the electronic device. In addition, differential pulse voltammetry reveals that the response of the electrochemical signals is rapid and sensitive, due to the synergistic effect of QDs and carbon nanotube-gold nanoparticles. Our study thus suggests that electrochemical sensing is an effective technology for detecting EMT and may have broad applications in analyzing various cell type transitions.


Assuntos
Técnicas Biossensoriais/instrumentação , Caderinas/isolamento & purificação , Eletroquímica/instrumentação , Eletroquímica/métodos , Transição Epitelial-Mesenquimal , Células A549 , Antígenos CD/isolamento & purificação , Eletrodos , Desenho de Equipamento , Ouro/química , Humanos , Nanopartículas Metálicas/química , Nanocompostos/química , Nanotubos de Carbono/química , Pontos Quânticos/química , Sensibilidade e Especificidade
12.
Analyst ; 145(4): 1110-1120, 2020 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-31916551

RESUMO

Electrochemical biosensors have been applied in a broad range of clinical applications for pathogen biomarker detection and medical applications and diagnosis due to the sensitivity of electrochemical methods and the bioselectivity of the components. The complexity of clinical conditions with various biofoulants (proteins, cells, polysaccharides and lipids) severely influences the reliability and stability of sensors for direct detection or immersion under changing conditions. Therefore, designing an antifouling sensing platform that can effectively reduce undesired binding to maintain biosensor performance in optimized analysis is necessary. For this purpose, the fundamental mechanisms of fouling materials and commonly used biocompatible antifouling components have been discussed, and the relevant effective modification strategies are introduced in this review. Recent advances in these strategies are demonstrated in examples with analysis of essential modification methods for reliable sensing in non-specific binding solutions or complex biofluids. The challenges and future perspectives of modification strategies for current clinical application are also discussed in this review.


Assuntos
Incrustação Biológica/prevenção & controle , Técnicas Biossensoriais/métodos , Eletroquímica/métodos , Humanos
13.
Analyst ; 145(4): 1087-1102, 2020 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-31922162

RESUMO

Fast-scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes (CFMEs) is a versatile electrochemical technique to probe neurochemical dynamics in vivo. Progress in FSCV methodology continues to address analytical challenges arising from biological needs to measure low concentrations of neurotransmitters at specific sites. This review summarizes recent advances in FSCV method development in three areas: (1) waveform optimization, (2) electrode development, and (3) data analysis. First, FSCV waveform parameters such as holding potential, switching potential, and scan rate have been optimized to monitor new neurochemicals. The new waveform shapes introduce better selectivity toward specific molecules such as serotonin, histamine, hydrogen peroxide, octopamine, adenosine, guanosine, and neuropeptides. Second, CFMEs have been modified with nanomaterials such as carbon nanotubes or replaced with conducting polymers to enhance sensitivity, selectivity, and antifouling properties. Different geometries can be obtained by 3D-printing, manufacturing arrays, or fabricating carbon nanopipettes. Third, data analysis is important to sort through the thousands of CVs obtained. Recent developments in data analysis include preprocessing by digital filtering, principal components analysis for distinguishing analytes, and developing automated algorithms to detect peaks. Future challenges include multisite measurements, machine learning, and integration with other techniques. Advances in FSCV will accelerate research in neurochemistry to answer new biological questions about dynamics of signaling in the brain.


Assuntos
Eletroquímica/métodos , Análise de Dados , Eletroquímica/instrumentação , Microeletrodos , Fatores de Tempo
14.
Analyst ; 145(4): 1158-1168, 2020 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-31922176

RESUMO

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


Assuntos
Dopamina/análise , Eletroquímica/métodos , Animais , Análise de Dados , Dopamina/química , Humanos , Fatores de Tempo
15.
Spectrochim Acta A Mol Biomol Spectrosc ; 230: 118081, 2020 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-32000061

RESUMO

The combination of surface-enhanced resonance Raman spectroscopy (SERRS) and electrochemistry is an ideal tool to study the redox process of the heme proteins and is often performed on silver electrodes. In this manuscript, we present an approach using a microstructured gold surface that serves as the electrochemical working electrode, and at the same time, acts as SERS active substrate. The cell requires a micromolar concentration of sample at the electrode surface. Even if the performance of the gold grid as SERS substrate exhibited a smaller enhancement factor than expected for silver, oxidized and reduced spectra of proteins (Сyt c, Hb and Mb) monolayers could be obtained and the characteristic redox dependent shifts of the marker bands ν19, ν4 and ν10 were seen. The easy modification protocol and the higher stability of the gold electrode towards oxidative currents are the advantages of the present spectroeletrochemical cell. Finally, FDTD simulations confirm that the roughness of the gold grid has an effect on the Raman enhancement of the adsorbed proteins.


Assuntos
Eletroquímica/métodos , Eletrodos , Ouro/química , Hemeproteínas/análise , Análise Espectral Raman/métodos , Animais , Oxirredução , Propriedades de Superfície
16.
Sensors (Basel) ; 20(3)2020 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-31979357

RESUMO

Interleukin 6 (IL-6), being a major component of homeostasis, immunomodulation, and hematopoiesis, manifests multiple pathological conditions when upregulated in response to viral, microbial, carcinogenic, or autoimmune stimuli. High fidelity immunosensors offer real-time monitoring of IL-6 and facilitate early prognosis of life-threatening diseases. Different approaches to augment robustness and enhance overall performance of biosensors have been demonstrated over the past few years. Electrochemical- and fluorescence-based detection methods with integrated electronics have been subjects of intensive research due to their ability to offer a better signal-to-noise ratio, high specificity, ultra-sensitivity, and wide dynamic range. In this review, the pleiotropic role of IL-6 and its clinical significance is discussed in detail, followed by detection schemes devised so far for their quantitative analysis. A critical review on underlying signal amplification strategies and performance of electrochemical and optical biosensors is presented. In conclusion, we discuss the reliability and feasibility of the proposed detection technologies for commercial applications.


Assuntos
Técnicas Biossensoriais/métodos , Técnicas Eletroquímicas/métodos , Interleucina-6/análise , Animais , Eletroquímica/métodos , Humanos
17.
Mikrochim Acta ; 187(1): 82, 2020 01 02.
Artigo em Inglês | MEDLINE | ID: mdl-31897862

RESUMO

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


Assuntos
Ácido Ascórbico/análise , Dopamina/análise , Eletroquímica/métodos , Estruturas Metalorgânicas/química , Nanocompostos/química , Nanoestruturas/química , Ácido Úrico/análise , Ácido Ascórbico/sangue , Dopamina/sangue , Eletroquímica/normas , Eletrodos , Grafite/química , Compostos de Nitrogênio/química , Prata , Compostos de Estanho , Titânio , Ácido Úrico/sangue
18.
Phys Chem Chem Phys ; 22(3): 997-1002, 2020 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-31691683

RESUMO

Chirality-induced spin selectivity is evidenced by exciting the spin resonance of radicals in an electrochemical cell where the working electrode is covered with a chiral self-assembled monolayer. Because the electron transfer to and from the paramagnetic radical is spin dependent, the electrochemical current changes at resonance. This electrically-detected magnetic resonance (EDMR) is monitored by a lock-in detection based on electrode voltage modulation, at a frequency that optimizes the sensitivity of the differential conductance to the electrode charge transfer process. The method is validated using p-doped GaAs electrodes in which the conduction band electrons are hyperpolarized by a well-known method of optical spin pumping with circularly polarized light. Gold electrodes covered with peptides consisting of 5 alanine groups (Al5) present a relative current change of up to 5 × 10-5 when the resonance condition is met, corresponding to a spin filtering efficiency between 6 and 19%.


Assuntos
Eletroquímica/métodos , Eletrodos , Espectroscopia de Ressonância Magnética , Reprodutibilidade dos Testes
19.
J Chromatogr A ; 1610: 460570, 2020 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-31607447

RESUMO

A major strength of capillary electrophoresis (CE) is its ability to inject small sample volumes. However, there is a great mismatch between injection volume (typically <100 nL) and sample volumes (typically 20-1500 µL). Electromigration-based sample preparation methods are based on similar principles as CE. The combination of these methods with capillary electrophoresis could tackle obstacles in the analysis of dilute samples. This study demonstrates coupling of three-phase microelectroextraction (3PEE) to CE for sample preparation and preconcentration of large volume samples while requiring minimal adaptation of CE equipment. In this set-up, electroextraction takes place from an aqueous phase, through an organic filter phase, into an aqueous droplet that is hanging at the capillary inlet. The first visual proof-of-concept for this set-up showed successful extraction using the cationic dye crystal violet (CV). The potential of 3PEE for bioanalysis was demonstrated by successful extraction of the biogenic amines serotonin (5-HT), tyrosine (Tyr) and tryptophan (Trp). Under optimized conditions limits of detection (LOD) were 15 nM and 33 nM for 5-HT and Tyr respectively (with Trp as an internal standard). These LODs are comparable to other similar preconcentration methods that have been reported in conjunction with CE. Good linearity (R2 > 0.9967) was observed for both model analytes. RSDs for peak areas in technical replicates, interday and intraday variability were all satisfactory, i.e., below 14%. 5-HT, Tyr and Trp spiked to human urine were successfully extracted and separated. These results underline the great potential of 3PEE as an integrated enrichment technique from biological samples and subsequent sensitive metabolomics analysis.


Assuntos
Eletroquímica/métodos , Eletroforese Capilar/métodos , Aminas Biogênicas/urina , Humanos , Concentração de Íons de Hidrogênio , Limite de Detecção , Sistemas On-Line , Reprodutibilidade dos Testes , Serotonina/urina , Fatores de Tempo , Urinálise
20.
Enzyme Microb Technol ; 132: 109384, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31731948

RESUMO

Cellulose triacetate (CTAB) synthesized by cellulose extracted from sugarcane bagasse, and commercial cellulose acetate (CA) were used to produce nanofiber membranes contained bromelain by electrospinning technique. About 1.3 g of cellulose acetate per gram of bagasse were obtained, and both CTAB and CA was characterized by analysis of Fourier Transform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC). The nanofiber membranes were produced by electrospinning process testing the following conditions: voltage 25 kV, flow rate 4 mL/h and distance 10 cm, using acetone/ dimethylformamide (DMF) (85:15 m/ m) to 15% cellulose triacetate (70% CA + 30% CTAB) or CA solutions. Scanning Electron Microscopy (SEM) was used to nanofiber membranes characterization. Bromelain was immobilized on the nanofiber membranes by crosslinking with glutaraldehyde and directly in the electrospinning step, the highest activity recovery was about 675% and in vitro controlled release tests were performed to semi-quantitatively evaluate the release of the enzyme bromelain thus demonstrating complete release process in 3 days.


Assuntos
Bromelaínas/química , Celulose/análogos & derivados , Eletroquímica/métodos , Nanofibras/química , Saccharum/química , Varredura Diferencial de Calorimetria , Celulose/química , Enzimas Imobilizadas/química , Microscopia Eletrônica de Varredura , Espectroscopia de Infravermelho com Transformada de Fourier
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