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1.
Bioelectrochemistry ; 129: 124-134, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31158797

RESUMO

The antioxidant properties of different plant extracts are usually claimed and used by food, medicine and cosmetic industry due to their health promoting capacities. In this study the presence of antioxidant compounds and the total antioxidant capacity of water-soluble extracts, prepared using two extraction methods and a variety of solvents, have been determined and a rapid screening method has been developed. Plant extracts characterisation, composition and antioxidant properties were confirmed by FTIR and Raman spectroscopies. Voltammetry, amperometry and electrochemical impedance were used to highlight the total antioxidant capacity of each extract using an electrochemical gold nanozyme-sensor based on the enzyme-like catalytic activity of gold nanoparticles. Both anodic area of cyclic voltammograms (10.31 µA V) and electrochemical index (153) calculated using differential potential voltammetry show the total content of antioxidant compounds, allowing to discriminate between different extracts. Amperometric total antioxidant capacity measurements were associated with those from classical chemiluminescence and good correlation has been found (Pearson's correlation coefficient of 0.958).


Assuntos
Antioxidantes/química , Técnicas Eletroquímicas/métodos , Ouro/química , Hippophae/química , Lavandula/química , Nanopartículas Metálicas/química , Extratos Vegetais/química , Antioxidantes/farmacologia , Técnicas Biossensoriais/métodos , Espectroscopia Dielétrica , Peróxido de Hidrogênio/química , Extratos Vegetais/farmacologia , Espectroscopia de Infravermelho com Transformada de Fourier
2.
Mol Biol (Mosk) ; 53(3): 467-475, 2019.
Artigo em Russo | MEDLINE | ID: mdl-31184612

RESUMO

Placenta is a highly specialized organ that is necessary for successful gestation. Several models of the placental barrier are used to study how it functions, including the transplacental transport of xenobiotics. One of these models, human choriocarcinoma cell line BeWo is widely used in vitro. Notably, cancerous BeWo cells form multilayer structures that normally are not found in the human placenta. Here, we aim to develop techniques suitable for monitoring BeWo b30 cells in culture. To assess the state of BeWo b30 cells growing on a membrane, we use impedance spectroscopy, which allows us to estimate the number of cell layers by the change in the electrical parameters of the biological system. In mature BeWo b30 cell cultures, we also note a significant increase in the expression of genes encoding metallothioneins (particularly, MT1B, MT1F, and MT2A) and syncytins (ERVW-1 and ERVFRD-1), which can be used as biomarkers reflecting the development of mature phenotypic characteristics, namely, trophoblastic invasion and formation of the syncytium.


Assuntos
Coriocarcinoma/genética , Coriocarcinoma/patologia , Espectroscopia Dielétrica , Perfilação da Expressão Gênica , Modelos Biológicos , Placenta/citologia , Placenta/metabolismo , Técnicas de Cultura de Células , Linhagem Celular Tumoral , Feminino , Humanos , Gravidez
3.
Talanta ; 201: 350-357, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31122434

RESUMO

In this work, a novel electrochemical biosensor has been fabricated based on step-by-step modification of a glassy carbon electrode (GCE) with methylene blue (MB)-DNA/multiwalled carbon nanotubes (MWCNTs)-chitosan (CS)/palladium nanoparticles (Pd NPs)/fullerene C60 (C60) for voltammetric and impedimetric detection of DNA damage induced by bisphenol A (BPA). Modifications applied to the GCE were characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy. The EIS and DPV responses of the biosensor were increased and decreased, respectively, by the DNA damage induced by BPA which led us to develop novel systems for detection of DNA damage. Our records confirmed that the biosensor was able to rapid and sensitive detection of DNA damage induced by BPA. Finally, according to the developed systems for detection of DNA damage, we have developed voltammetric and impedimetric methods for determination of BPA.


Assuntos
Compostos Benzidrílicos/efeitos adversos , Compostos Benzidrílicos/análise , Dano ao DNA/efeitos dos fármacos , DNA/química , Fenóis/efeitos adversos , Fenóis/análise , Técnicas Biossensoriais/instrumentação , Técnicas Biossensoriais/métodos , Quitosana/química , Espectroscopia Dielétrica/métodos , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Limite de Detecção , Nanopartículas Metálicas/química , Azul de Metileno/química , Nanotubos de Carbono/química , Paládio/química , Reprodutibilidade dos Testes
4.
Biosens Bioelectron ; 138: 111310, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31103014

RESUMO

In this work, we detail the progress of a novel electrochemical disposable device, which has a relatively low cost and easy production, with a novel conductive ink, that consists of graphite and automotive varnish mixture, deposited over a self-adhesive paper, granting an easy production with relatively low cost. The electrode surface was characterized by scanning electron microscopy, X-ray powder diffraction and Fourier transforms infrared and Raman, cyclic voltammetry and electrochemical impedance spectroscopies. In addition, the proposed electrode was applied for individual electrochemical determination of dopamine and serotonin. The device achieved a linear response between 30 and 800 µmol L-1 and a limit of detection (LOD) of 0.13 µmol L-1, by square wave voltammetry for dopamine and a linear range from 6.0 to 100 µmol L-1, with a LOD of 0.39 µmol L-1, by differential pulse voltammetry for serotonin. Later, the working electrode was modified with glucose oxidase and dihexadecyl phosphate film in order to obtain a biosensor. At this stage, CV was applied to detect glucose in the range of 1.0-10 µmol L-1 and LOD of 0.21 µmol L-1. By three different techniques and analytes, the sensoring and biosensoring processes presented high reproducibility. The proposed adhesive electrode is easy to prepare, disposable, within non-restrictive nature, which allows an approach of a new device for electrochemical sensing and biosensing.


Assuntos
Técnicas Biossensoriais/instrumentação , Dopamina/análise , Glucose/análise , Neurotransmissores/análise , Papel , Serotonina/análise , Espectroscopia Dielétrica , Condutividade Elétrica , Técnicas Eletroquímicas , Eletrodos , Glucose Oxidase/química , Grafite/química , Tinta , Limite de Detecção , Organofosfatos/química , Reprodutibilidade dos Testes
5.
Biosens Bioelectron ; 138: 111322, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31112916

RESUMO

Tuberculosis caused by Mycobacterium tuberculosis (M. tuberculosis) remains one of the most serious infectious diseases all over the world. The key to reduce the spread and mortality rate of tuberculosis is to develop faster and more sensitive approaches for detection of M. tuberculosis. However, current detection methods can not meet the requirements of rapid clinical M. tuberculosis detection in terms of detection time. Herein, a new 16S rDNA multichannel series piezoelectric quartz crystal (MSPQC) sensor based on Exonuclease III (Exo III)-aided target recycling has been developed for rapid detection of M. tuberculosis. The specific 16S rDNA fragment of M. tuberculosis was used as biomarker, DNA capture probes complementary to the biomarker were designed and modified on the surface of AuNPs. The Exo III which could recognise hybrid duplexes and selectively digest DNA capture probe was used to assist digestion cycle by digesting DNA capture probe and releasing the intact target fragment. After all DNA probes loading on the surface of AuNPs were removed, the surface of AuNPs was exposed and conductive connection was formed between the nanogap network electrode by self-catalytic growth of exposed AuNPs in the glucose and HAuCl4 solution. This resulted in sensitive response of M. tuberculosis sensor and M. tuberculosis was detected by recording this response. The limit of detection (LOD) of the method was 20 CFU/mL and the detection time was less than 3 h. It was expected to be widely used in detection methods of M. tuberculosis.


Assuntos
DNA Ribossômico/análise , Exodesoxirribonucleases/química , Mycobacterium tuberculosis/genética , Técnicas Biossensoriais/instrumentação , Técnicas Biossensoriais/métodos , Espectroscopia Dielétrica , Eletrodos , Ouro/química , Humanos , Limite de Detecção , Nanopartículas Metálicas/química , Mycobacterium tuberculosis/isolamento & purificação , Técnicas de Amplificação de Ácido Nucleico , Quartzo/química , Sensibilidade e Especificidade
6.
Anal Chim Acta ; 1071: 78-85, 2019 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-31128758

RESUMO

The development of a low-cost and disposable biosensing technologies has received a great interest of healthcare for the sensitive and reliable detection of single nucleotide mutation related to single nucleotide polymorphisms (SNPs). In the present study, an impedimetric biosensing platform based on zip nucleic acids (ZNA) was developed for the sensitive detection of Factor V Leiden (FV Leiden) mutation. After optimization of experimental parameters, the sequence selective hybridization between ZNA probe and target related to FV Leiden mutation was evaluated via electrochemical impedance spectroscopy technique (EIS) by measuring changes at the charge transfer resistance, Rct. Sensitive and selective impedimetric analysis was performed using carbon nanofiber (CNF) modified screen printed electrodes (SPE) and multi-channel screen printed array of electrodes (MULTIx8 CNF-SPE) resulting in a relatively shorter time in comparison to conventional methods. The selectivity of ZNA probe to mutation-free DNA sequences was also investigated. The applicability of single-use ZNA biosensor was also tested in synthetic PCR samples containing a single base mutation.


Assuntos
Sondas de DNA/química , DNA/análise , Fator V/genética , Técnicas Biossensoriais/métodos , Carbono/química , DNA/genética , Sondas de DNA/genética , Espectroscopia Dielétrica/métodos , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Limite de Detecção , Nanofibras/química , Hibridização de Ácido Nucleico , Mutação Puntual
7.
Bioelectrochemistry ; 129: 54-61, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31103847

RESUMO

OBJECTIVE: The aim of this research was to investigate if dielectric spectroscopy between 100 Hz and 1 MHz provides reliable information about water distribution in ischaemic heart tissue and to investigate the influence of temperature on oedema formation. METHODS: We examined hearts of landrace piglets (n = 13) during ischaemia at 35 °C, 25 °C, and 15 °C. The dielectric permittivity ε'(f) and conductivity σ'(f) were calculated from impedance spectra measured between 100Hz and 1MHz. Gap junction uncoupling (GJU) was identified in the sigmoidal time course of ε'(13 kHz). The extracellular space index (ECSI) was estimated by the ratio σ'(100 Hz)/σ'(1 MHz). Intercalated water was analysed in electron microscopy images of the myocardial samples and was used to calculate the extracellular space index ECSIhisto. The ECSI and ECSIhisto were compared during ischaemia. GJU and oedema formation were simulated with an electrical heart model. RESULTS: At the onset of ischaemia, the ECSI was significantly higher than the ECSIhisto (p < .01). GJU during ischaemia was temperature-dependent. After GJU, the values of the ECSI and ECSIhisto matched very well. The simulations confirmed the influence of GJU on the ECSI. SIGNIFICANCE: The estimation of cell oedema with the ECSI is reliable only after GJU. The development of oedema estimated by the ECSI was delayed at cooler temperatures.


Assuntos
Espectroscopia Dielétrica/instrumentação , Edema Cardíaco/patologia , Isquemia Miocárdica/patologia , Miocárdio/patologia , Animais , Espectroscopia Dielétrica/métodos , Edema Cardíaco/etiologia , Desenho de Equipamento , Junções Comunicantes/patologia , Isquemia Miocárdica/complicações , Suínos
8.
Bioelectrochemistry ; 129: 79-89, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31125924

RESUMO

When implantable recording devices for brain or neural electrical activity are designed, the number of available materials for electrodes is quite limited. The material must be biocompatible with respect to ISO10993, its electrochemical properties must remain stable and the response of cells or tissues can be mitigated, especially on the glial scar. This involves electrode characterization pre- implantation and impedance spectroscopy during chronic implantation, in order to evaluate both electrode properties and performance. This study was aimed at a comparison of the long-term behavior of a nanostructured boron-doped diamond (BDD) with a nanostructured Platinum Iridium (PtIr) electrode. Firstly, a batch of cortical grids with bare and modified contacts (2 mm in diameter) was engineered for implantation. Secondly a miniature swine model was developed. This study highlighted the predominant role of electrode surface roughness on the quality of recordings. Rough PtIr contacts and BDD coated ones showed comparable behavior after three-month implantation with a slight increase of the modulus of the impedance and a tissue capsule. Nevertheless, immunohistochemistry analysis did not exhibit either a toxic or irritation reaction. With regard to biocompatibility, promising long term results are shown for both materials.


Assuntos
Materiais Biocompatíveis/química , Boro/química , Diamante/química , Eletrodos Implantados , Nanoestruturas/química , Animais , Materiais Biocompatíveis/efeitos adversos , Boro/efeitos adversos , Encéfalo/ultraestrutura , Diamante/efeitos adversos , Espectroscopia Dielétrica , Técnicas Eletroquímicas , Eletrodos Implantados/efeitos adversos , Proteína Glial Fibrilar Ácida/análise , Nanoestruturas/efeitos adversos , Nanoestruturas/ultraestrutura , Suínos , Porco Miniatura
9.
Bioelectrochemistry ; 128: 252-262, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31048108

RESUMO

Biocorrosion is an important type of corrosion which leads to economic losses across oil and gas industries, due to increased monitoring, maintenance, and a reduction in platform availability. Ideally, a chemical compound engineered to mitigate against biocorrosion would possess both antimicrobial properties, as well as efficient corrosion inhibition. Gemini surfactants have shown efficacy in both of these properties, however there still remains a lack of electrochemical information regarding biocorrosion inhibition. The inhibition of corrosion and biocorrosion, by cationic gemini surfactants, of carbon steel was investigated. The results showed that the inhibition efficiency of the gemini surfactants was high (consistently >95%), even at low concentrations. Gemini surfactants also showed strong antimicrobial activity, with a minimum inhibitory concentration (0.018 mM). Corrosion inhibition was investigated by electrochemical impedance spectroscopy (EIS) and linear polarisation resistance (LPR), with biocorrosion experiments carried out in an anaerobic environment. Surface morphology was analysed using scanning electron microscopy (SEM).


Assuntos
Antibacterianos/farmacologia , Biofilmes , Corrosão , Compostos de Amônio Quaternário/farmacologia , Aço/química , Tensoativos/farmacologia , Espectroscopia Dielétrica , Microscopia Eletrônica de Varredura
10.
Soft Matter ; 15(21): 4334-4345, 2019 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-31073564

RESUMO

Supercooled liquid secondary amides display an electrical absorption peak characterized by an almost Debye-like shape, indicative of a close-to-exponential polarization response. This response, believed to be supramolecular in nature, is so enormously intense that the amide's structural process, contributing only a few percent to the total relaxation strength, is hard to resolve reliably using standard dielectric spectroscopy. To overcome this issue, nonlinear dielectric spectroscopy involving field-induced structural recovery and temperature-induced physical aging, was applied near the calorimetric glass transition of a mixture of N-methylformamide and N-ethylacetamide. Without the need to rely on cumbersome deconvolution procedures, it is thus demonstrated that the supramolecular response is by a factor of 6 slower than the structural relaxation. Conversely, in linear rheological experiments only the structural relaxation could be resolved, but not the supramolecular one. However, medium-amplitude oscillatory shear experiments carried out at 160 K do reveal the supramolecular process. Hence, the combination of linear and nonlinear mechanical measurements corroborates the dielectrically uncovered spectral separation of the two processes.


Assuntos
Peptídeos/química , Reologia , Temperatura Ambiente , Espectroscopia Dielétrica , Fenômenos Mecânicos , Dinâmica não Linear , Resistência ao Cisalhamento
11.
Chem Commun (Camb) ; 55(39): 5611-5614, 2019 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-31025670

RESUMO

A hexagonal FeSe nanoparticle anode with a novel reaction mechanism and mechanical stability may fully facilitate the desirable rate capability and cycling performance in sodium-ion batteries. In situ TEM reveals that hexagonal FeSe nanoparticle transition to the Fe and Na2Se phase during sodiation, while the products transform to the tetragonal FeSe phase after desodiation.


Assuntos
Nanopartículas/química , Sódio/química , Espectroscopia Dielétrica , Condutividade Elétrica , Fontes de Energia Elétrica , Ferro/química , Selênio/química
12.
Mater Sci Eng C Mater Biol Appl ; 101: 88-91, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31029367

RESUMO

Cancer Biomarkers are important biological molecules which provide early detection, diagnosis and classification of cancer cells. In this work, nanoparticle tags with different redox potentials have been used as an electrochemical coding technology for the simultaneous detection of carcinoembryonic antigen (CEA), vascular endothelial growth factor (VEGF) and α-fetoprotein (AFP) biomarkers. As far as we know, this is the only work that covers the simultaneous detections of these biomarkers. For this purpose, basically, an electrochemical sandwich immunosensor, which was fabricated from carbon screen printed electrode, was utilized as a diagnostic platform. As nanoparticle tags, PbAu@É£Fe2O3, CuAu@É£Fe2O3 and ZnAu@É£Fe2O3 hybrid nanolabels were synthesized and used for labelling anti-CEA, anti-VEGF and anti-AFP, respectively. By monitoring differential pulse voltammetric oxidation peaks of labeling metals (Pb, Cu, Zn), CEA, VEGF and AFP biomarkers were detected at the same time.


Assuntos
Biomarcadores Tumorais/análise , Técnicas Biossensoriais/métodos , Antígeno Carcinoembrionário/análise , Imunoensaio/métodos , Fator A de Crescimento do Endotélio Vascular/análise , alfa-Fetoproteínas/análise , Anticorpos/metabolismo , Espectroscopia Dielétrica , Técnicas Eletroquímicas , Humanos , Nanopartículas/química , Oxirredução
13.
Bioresour Technol ; 284: 148-154, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30928826

RESUMO

Anode with good electrocatalytic capabilities is more specifically required to reduce the ohimic losses during microbial fuel cell (MFC) operation. Highly conductive polymers viz., Polyaniline (PANi) and Polyaniline/Carbon nanotube (PANi/CNT) composite were prepared by in situ oxidative chemical polymerization method. Anodes were fabricated independently by coating PANi and CNT/PANi composites on the surface of SSM. The fabricated electrodes were evaluated as anode against stainless steel mess (SSM) as cathode during MFC operation. Maximum bioelectricity generation was observed in SSM-PANi/CNT-anode with power density of 48 mW/m2 and COD removal efficiency of 80% compared with SSM-PANi-anode (38 mW/m2; 65%) and SSM-anode (28 mW/m2; 58%). Bioelectrochemical characterization of the electrode materials using cyclic voltammetry and electrochemical impedance spectroscopy showed high electrocatalytic activity of PANi/CNT composite electrode. The study concluded the efficiency of PANi/CNT composite electrodes as bioanode in operation of MFCs towards achieving increased bioelectricity production along with wastewater treatment.


Assuntos
Compostos de Anilina/química , Nanotubos de Carbono/química , Fontes de Energia Bioelétrica , Espectroscopia Dielétrica , Condutividade Elétrica , Eletrodos , Polímeros/química
14.
Mater Sci Eng C Mater Biol Appl ; 100: 396-410, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30948076

RESUMO

Stainless steel (SS) has been widely applied as one of the most efficient implant metal materials, although corrosion and infection in body environment are still challenging. Herein, an antibacterial passivation method was employed to enhance the antibacterial performance and corrosion resistance of the medical 316L SS. The result proved that the antibacterial-passivated 316L SS exhibited stable antibacterial activity and effectively inhibited the formation of bacterial biofilm. Electrochemical measurements combined with X-ray photoelectron spectroscopy technique were used to study the corrosion resistance and semiconductor behavior of passivated 316L SS immersed in simulated physiological environment. The results indicated that the 316L SS after antibacterial passivation treatment for 1 h, soaking in the medium for 10 days, showed satisfactory corrosion resistance attributing to proper Cu deposition in the passive film. The anodic stripping voltammetry measurement further confirmed that the Cu-bearing passive film could continuously release Cu ions into medium. The zebrafish test demonstrated an excellent in vivo biocompatibility for the 316L SS with antibacterial passivation for 0.5 and 1 h, respectively. In addition, changes of surface roughness, contact angle and chemical composition after antibacterial passivation played an important role in explaining the antibacterial mechanism, which could be clearly divided into contact killing and ionic release killing. Hence, the antibacterial passivation treatment was preliminarily proved as a potential way for enhancing the persistent antibacterial activity and corrosion resistance of 316L SS.


Assuntos
Antibacterianos/farmacologia , Materiais Biocompatíveis/farmacologia , Aço Inoxidável/farmacologia , Animais , Biofilmes/efeitos dos fármacos , Morte Celular/efeitos dos fármacos , Cobre/análise , Corrosão , Espectroscopia Dielétrica , Eletroquímica , Eletrodos , Embrião não Mamífero/citologia , Embrião não Mamífero/efeitos dos fármacos , Viabilidade Microbiana/efeitos dos fármacos , Microscopia de Força Atômica , Espectroscopia Fotoeletrônica , Propriedades de Superfície , Água/química , Peixe-Zebra/embriologia
15.
Mater Sci Eng C Mater Biol Appl ; 100: 897-914, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30948127

RESUMO

A novel random copolymer 4, containing diallylmethylamine and N1,N1-diallyl-N1-methyl-N6,N6,N6-tripropylhexane-1,6-diammonium dibromide units in a 1:1 ratio (polymer 4) was synthesized via Butler's cyclopolymerization technique. Characterization was accomplished by 1H NMR, elemental analysis, and Fourier-transform infrared spectroscopy (FTIR). Polymer 4 was tested as corrosion inhibitor for low carbon steel in 15% HCl solution via gravimetric and electrochemical approaches. The analysis of the metal specimen surfaces was done using scanning electron microscope (SEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDAX), and X-ray photoelectron spectroscopy (XPS) methods. Polymer 4 is inhibitor for the substrate particularly at elevated temperatures. Corrosion mitigation is by chemisorption mechanism and can be best described with the Langmuir and El-Awady et al. kinetic-thermodynamic adsorption isotherms. Polymer 4 corrosion mitigation capacity can be improved by the addition of a minute amount of I- ions. Inhibition efficiency of 92.99% has been achieved with 500 ppm polymer 4 + 1 mM KI mixture at 25 °C. Surface analysis results support the claim of adsorption of additive molecules on steel surface. From XPS results, corrosion products on steel surface exposed to the free acid solution are mixtures of chlorides, carbonates, oxides, and hydroxides. In polymer 4 + KI system, polymer 4 molecules are adsorbed on triiodide and pentaiodide ions layer. The improved corrosion inhibition of polymer 4 by I- ions is synergistic in nature according to calculated synergism parameter. Polymer 4 is a promising corrosion inhibitor for oil well acidizing purpose.


Assuntos
Ácidos/química , Metilaminas/química , Polímeros/química , Adsorção , Corrosão , Ciclização , Espectroscopia Dielétrica , Eletroquímica , Elementos , Concentração de Íons de Hidrogênio , Metilaminas/síntese química , Microscopia de Força Atômica , Espectroscopia Fotoeletrônica , Polímeros/síntese química , Espectroscopia de Prótons por Ressonância Magnética , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura Ambiente
16.
Sensors (Basel) ; 19(7)2019 Apr 09.
Artigo em Inglês | MEDLINE | ID: mdl-30970595

RESUMO

A highly sensitive glucose sensor was prepared by a one-step method using 3-aminophenyl boronic acid as a unit of recognition and a screen-printed carbon electrode (SPCE) as an electrochemical transducer. Scanning Electron Microscopy confirmed the success of the functionalization of the SPCE due to the presence of clusters of boronic acid distributed on the carbon surface. In agreement with the Electrochemical Impedance Spectroscopy (EIS) tests performed before and after the functionalization, Cyclic Voltammetry results indicated that the electroactivity of the electrode decreased 37.9% owing to the presence of the poly phenylboronic acid on the electrode surface. EIS revealed that the sensor was capable to selectively detect glucose at a broad range of concentrations (limit of detection of 8.53 × 10-9 M), not recognizing fructose and sucrose. The device presented a stable impedimetric response when immediately prepared but suffered the influence of the storage time and some interfering species (dopamine, NaCl and animal serum). The response time at optimized conditions was estimated to be equal to 4.0 ± 0.6 s.


Assuntos
Técnicas Biossensoriais , Ácidos Borônicos/química , Técnicas Eletroquímicas , Glucose/isolamento & purificação , Carbono/química , Espectroscopia Dielétrica , Eletrodos , Glucose/química , Ouro/química , Humanos , Limite de Detecção , Microscopia Eletrônica de Varredura , Polímeros/química , Soro/química
17.
Sensors (Basel) ; 19(7)2019 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-30974770

RESUMO

The knowledge of frequency and temperature dependent dielectric properties of tissue is essential to develop ultra-wideband diagnostic technologies, such as a non-invasive temperature monitoring system during hyperthermia treatment. To this end, we characterized the dielectric properties of animal liver, muscle, fat and blood in the microwave frequency range from 0.5 GHz to 7 GHz and in the temperature range between 30 °C and 50 °C. The measured data were modeled to a two-pole Cole-Cole model and a second-order polynomial was introduced to fit the Cole-Cole parameters as a function of temperature. The parametric model provides access to the dielectric properties of tissue at any frequency and temperature in the specified range.


Assuntos
Sangue/efeitos da radiação , Espectroscopia Dielétrica , Micro-Ondas , Temperatura Ambiente , Algoritmos , Animais , Impedância Elétrica , Gorduras/efeitos da radiação , Humanos , Fígado/fisiologia , Fígado/efeitos da radiação , Modelos Biológicos , Músculos/fisiologia , Músculos/efeitos da radiação , Suínos
18.
Bioelectrochemistry ; 128: 211-217, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31030173

RESUMO

In this study, an effective electrochemical sensor was developed for heparin detection using a protamine-conjugated graphene oxide/gold (GO/Au) composite. Protamine is an antidote that can act as an affinity ligand for heparin. The GO was used as support for signal amplification, and Au nanoparticles (NPs) were employed to immobilize the protamine. This Au NPs also increasing the electron transfer rate and enhancing the signal response during protamine-heparin integration. The proposed affinity sensor had a simple fabrication process, a low detection limit (0.9 nM), a wide linear range (1.9 × 10-7 M to 1.5 × 10-9 M), high stability, and high selectivity in the detection of heparin.


Assuntos
Técnicas Eletroquímicas/instrumentação , Ouro/química , Grafite/química , Heparina/análise , Protaminas/química , Espectroscopia Dielétrica , Limite de Detecção , Microscopia Eletrônica de Transmissão , Espectroscopia Fotoeletrônica , Reprodutibilidade dos Testes , Análise Espectral Raman , Difração de Raios X
19.
Environ Sci Pollut Res Int ; 26(14): 14693-14702, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30945079

RESUMO

Ball-milled biochars (BM-biochars) were produced through ball milling of pristine biochars derived from different biomass at three pyrolysis temperatures (300, 450, and 600 °C). The results of scanning electron microscopic (SEM), surface area, hydrodynamic diameter test, and Fourier transform infrared spectroscopy (FTIR) revealed that BM-biochars had smaller particle size (140-250 nm compared to 0.5-1 mm for unmilled biochar), greater stability, and more oxygen-containing functional groups (2.2-4.4 mmol/g compared to 0.8-2.9 for unmilled biochar) than the pristine biochars. With these changes, all the BM-biochar-modified glassy carbon electrodes (BM-biochar/GCEs) exhibited prominent electrochemical properties (e.g., ΔEp of 119-254 mV compared to 850 mV for bare GCE). Cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) show that ball-milled 600 °C biochar/GCE (BMBB600/GCE and BMBG600/GCE) had the smallest peak-to-peak separation (ΔEp = 119 and 132 mV, respectively), series resistance (RS = 88.7 and 89.5 Ω, respectively), and charge transfer resistance (RCT = 1224 and 1382 Ω, respectively), implying its best electrocatalytic activity for the reduction of Fe(CN)63-. It is supposed that the special structure (i.e., internal surface area, pore volume, oxygen-containing functional groups, and graphitic structure) facilitates the electron transfer and reduces interface resistance. Economic cost of BM-biochar/GCE was 1.97 × 10-7 USD/cm2, much lower than that of a "low-cost platinum electrode" (0.03 USD/cm2). The results indicate potential application of the novel BM-biochar for low cost and high efficient electrodes. Graphical abstract.


Assuntos
Carvão Vegetal/química , Eletrodos , Carbono , Custos e Análise de Custo , Espectroscopia Dielétrica/instrumentação , Condutividade Elétrica , Eletrodos/economia , Microscopia Eletrônica de Varredura , Oxigênio/química , Tamanho da Partícula , Pirólise , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura Ambiente
20.
Anal Chim Acta ; 1065: 12-20, 2019 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-31005144

RESUMO

We are reporting an innovative building-block for the development of biosensors based on the non-covalent functionalization of multi-walled carbon nanotubes (MWCNTs) with avidin (MWCNTs-avidin). In this work, at variance with previous reports, avidin has the double role of simultaneously being the exfoliating agent of MWCNTs and the platform for anchoring different biotinylated biomolecules. The optimum dispersion was obtained by sonicating for 5.0 min 0.50 mgmL-1 MWCNTs with 1.00 mgmL-1 avidin solution prepared in 50:50 v/v ethanol/water. As proof-of-concept, we immobilized biotinylated horseradish peroxidase (b-HRP) at glassy carbon electrodes (GCE) modified with MWCNTs-avidin to develop a hydrogen peroxide biosensor using hydroquinone as redox mediator. Surface plasmon resonance, electrochemical impedance spectroscopy, cyclic voltammetry and amperometry demonstrated that, even after the partial denaturation of avidin due to the drastic conditions used to functionalize the MWCNTs, it preserves the biorecognition properties and efficiently interacts with biotinylated horseradish peroxidase (b-HRP). The analytical characteristics of the resulting hydrogen peroxide biosensor are the following: linear range between 1.0 × 10-6 M and 1.4 × 10-5 M, sensitivity of (1.37 ±â€¯0.04) x 105 µAM-1, detection limit of 24 nM and reproducibility of 2.9%. The sensor was challenged with different samples, a mouthwash solution, human blood serum and milk, with very good performance.


Assuntos
Avidina/química , Técnicas Biossensoriais , Técnicas Eletroquímicas , Peroxidase do Rábano Silvestre/metabolismo , Peróxido de Hidrogênio/análise , Nanotubos de Carbono/química , Animais , Espectroscopia Dielétrica , Eletrodos , Peroxidase do Rábano Silvestre/química , Humanos , Leite/química , Ressonância de Plasmônio de Superfície
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