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1.
J Chem Phys ; 151(14): 144712, 2019 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-31615232

RESUMO

Electrogenerated chemiluminescence (ECL) is a promising technique for low concentration molecular detection. To improve the detection limit, plasmonic nanoparticles have been proposed as signal boosting antennas to amplify ECL. Previous ensemble studies have hinted that spectral overlap between the nanoparticle antenna and the ECL emitter may play a role in signal enhancement. Ensemble spectroscopy, however, cannot resolve heterogeneities arising from colloidal nanoparticle size and shape distributions, leading to an incomplete picture of the impact of spectral overlap. Here, we isolate the effect of nanoparticle-emitter spectral overlap for a model ECL system, coreaction of tris(2,2'-bipyridyl)dichlororuthenium(ii) hexahydrate and tripropylamine, at the single-particle level while minimizing other factors influencing ECL intensities. We found a 10-fold enhancement of ECL among 952 gold nanoparticles. This signal enhancement is attributed exclusively to spectral overlap between the nanoparticle and the emitter. Our study provides new mechanistic insight into plasmonic enhancement of ECL, creating opportunities for low concentration ECL sensing.


Assuntos
Nanopartículas Metálicas/química , Compostos Organometálicos/química , Propilaminas/química , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Ouro/química , Ouro/efeitos da radiação , Luz , Luminescência , Medições Luminescentes/métodos , Nanopartículas Metálicas/efeitos da radiação , Compostos Organometálicos/efeitos da radiação
2.
Chemosphere ; 235: 1189-1196, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31561310

RESUMO

A high oxygen evolution potential (2.6V) and conductivity of Ti/TiO2 NTs/Ta2O5-PbO2 anode was fabricated by mixed metal oxide. A well-aligned TiO2 nanotubes was successfully prepared by using 1-butyl-3-methylimidazolium tetrafluoroborate as the electrolyte. The surface structure of anodes were characterized by scanning electron microscope, X-ray diffraction and energy dispersive X-ray spectroscopy. During the electrochemical degradation experiments, the effects of different anodes, current density, initial pH value and concentration were discussed. The results showed that co-doped Ta2O5 coating is an effective method to improve the surface morphology and the electrochemical characterization of Ti/TiO2 NTs/PbO2. At the initial pH value of 3 and current density of 12 mA cm-2, the removal rates of Acid Orange 7 and total organic carbon with Ti/TiO2 NTs/Ta2O5-PbO2 anode were almost 100% and 98.3%. Comparing with Ti/PbO2 anode at the same charge consumption (3 A h L-1), the instantaneous current efficiency of the Ti/TiO2 NTs/Ta2O5-PbO2 anode and Ti/TiO2 NTs/PbO2 anode increased by 40.0% and 27.1%, respectively. The highest rate of k.OH on Ti/TiO2 NTs/Ta2O5-PbO2 anode was 12.4 µmol (L min)-1. The organic dyes are oxidized into CO2 and H2O by .OH radical. The reaction process and mechanism during the electrochemical degradation were discussed.


Assuntos
Corantes/química , Técnicas Eletroquímicas/métodos , Nanotubos/química , Titânio/química , Compostos Azo , Benzenossulfonatos , Eletrodos , Oxirredução , Óxidos/química
3.
Chem Commun (Camb) ; 55(80): 12040-12043, 2019 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-31531449

RESUMO

A visible light-induced self-powered sensor for the detection of tyrosinase activity was proposed. A tyrosinase-responsive photoelectrochemical-chemical redox cycling strategy was integrated with a photofuel cell for signal amplification.


Assuntos
Técnicas Biossensoriais/métodos , Monofenol Mono-Oxigenase/análise , Nanoestruturas/química , Técnicas Biossensoriais/instrumentação , Bismuto/química , Catálise , Catecóis/química , Fontes de Energia Elétrica , Técnicas Eletroquímicas/métodos , Eletrodos , Grafite/química , Hemina/química , Luz , Nitrilos/química , Oxirredução , Fosfinas/química , Sulfetos/química
4.
Chem Commun (Camb) ; 55(70): 10380-10383, 2019 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-31397448

RESUMO

A strategy for the photoelectrochemical detection of miRNA with ultra-low background noise was developed using tungsten diselenide-cysteine-dopamine (WSe2/Cys/DA) as a nanoprobe coupled with mismatched catalytic hairpin assembly target recycling. A superior detection limit of 3.3 aM toward miRNA-221 was achieved.


Assuntos
Cisteína/química , Dopamina/química , Técnicas Eletroquímicas/métodos , MicroRNAs/análise , Sondas Moleculares/química , Nanoestruturas , Processos Fotoquímicos , Selênio/química , Tungstênio/química , Técnicas Biossensoriais , Catálise , Humanos , Limite de Detecção , MicroRNAs/sangue , Estudo de Prova de Conceito
5.
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
6.
Chem Commun (Camb) ; 55(71): 10603-10606, 2019 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-31424058

RESUMO

A truly ratiometric homogeneous electrochemical biosensor has been developed for sensitive miRNA detection based on the unique diffusion/intercalation properties of electroactive dyes without the need for electrode modification or materials preparation.


Assuntos
Técnicas Biossensoriais/métodos , Corantes/química , Técnicas Eletroquímicas/métodos , Substâncias Intercalantes/química , MicroRNAs/análise , DNA/química , Eletrodos , Exodesoxirribonucleases/química , Compostos Ferrosos/química , Limite de Detecção , Metalocenos/química , Azul de Metileno/química , Oxirredução
7.
Braz J Cardiovasc Surg ; 34(4): 464-471, 2019 08 27.
Artigo em Inglês | MEDLINE | ID: mdl-31454201

RESUMO

OBJECTIVE: Cerebrospinal fluid (CSF) drainage is a technique that has significantly reduced the incidence of spinal cord ischaemia (SCI). We present results of a systematic review to assess the literature on this topic in relation to thoracoabdominal aortic aneurysm repair (TAAR). METHODS: Major medical databases were searched to identify papers related to CSF biomarkers measured during TAAAR. RESULTS: Fifteen papers reported measurements of CSF biomarkers with 265 patients in total. CSF biomarkers measured included S-100ß, neuron-specific endolase (NSE), lactate, glial fibrillary acidic protein A (GFPa), Tau, heat shock protein 70 and 27 (HSP70, HSP27), and proinflammatory cytokines. Lactate and S-100ß were reported the most, but did not correlate with SCI, which was also the case with NSE and TAU. GFPa showed significant CSF level rises, both intra and postoperative in patients who suffered SCI and warrants further investigation, similar results were seen with HSP70, HSP27 and IL-8. CONCLUSIONS: Although there is significant interest in this topic, there still remains a significant lack of high-quality studies investigating CSF biomarkers during TAAR to detect SCI. A large and multicentre study is required to identify the significant role of each biomarker.


Assuntos
Aneurisma da Aorta Torácica/cirurgia , Biomarcadores/líquido cefalorraquidiano , Técnicas Eletroquímicas/métodos , Fosfopiruvato Hidratase/sangue , Isquemia do Cordão Espinal/líquido cefalorraquidiano , Biomarcadores/sangue , Drenagem , Humanos , Ácido Láctico/sangue , Ácido Láctico/líquido cefalorraquidiano , Proteínas S100/sangue , Proteínas S100/líquido cefalorraquidiano , Isquemia do Cordão Espinal/sangue
8.
Anal Bioanal Chem ; 411(23): 6049-6056, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31280477

RESUMO

As an important glycoprotein of the lectin family, soybean agglutinin (SBA) is an anti-nutritional factor with considerable toxic and side effects and plays a significant role in tumor analysis. In order to achieve the sensitive detection of SBA, a sandwich-structured electrochemiluminescence (ECL) biosensor was constructed using carboxylated carbon nitride (C-g-C3N4) as luminophore and D-galactosamine (galM) as a recognition element. A glassy carbon electrode (GCE) was modified with Au nanoparticles (Au NPs) for capturing the galM via Au-N bond, and further capturing the target SBA by specific recognition between galM and SBA. In the presence of SBA, the composite C-g-C3N4-galM was immobilized onto the electrode. With the increase in the concentration of SBA, the ECL signal from C-g-C3N4 increased, thus achieving a signal-on detection of SBA. The linear range of the biosensor was 1.0 ng/mL~10 µg/mL and detection limit for SBA was as low as 0.33 ng/mL. In this construction strategy, C-g-C3N4 not only acted as an excellent signal probe, but also as an immobilization matrix to easily achieve a high loading of the small molecule recognition element galM. This strategy provides a simple alternative SBA detection platform. Graphical abstract.


Assuntos
Galactosamina/química , Grafite/química , Substâncias Luminescentes/química , Nitrilos/química , Lectinas de Plantas/análise , Proteínas de Soja/análise , Técnicas Biossensoriais/métodos , Ácidos Carboxílicos/química , Técnicas Eletroquímicas/métodos , Ouro/química , Humanos , Limite de Detecção , Medições Luminescentes/métodos , Nanopartículas Metálicas/química , Lectinas de Plantas/sangue , Proteínas de Soja/sangue
9.
Food Chem ; 300: 125189, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31325754

RESUMO

Since the intake of quercetin glucosides has healthy benefits, the analysis of quercetin glucosides in food is useful. The electrochemical determination of individual quercetin glucosides (quercetin-3-glucoside (Q3G), quercetin-4'-glucoside (Q4'G), and quercetin-3,4'-diglucoside (Q34'G)) in food is carried out. For the detection of quercetin glucosides, a long-length carbon nanotube electrode offers attractive properties such as well-defined current peaks, high sensitivity, and high reproducibility. Cyclic voltammetry (CV) demonstrates distinct and specific peak currents: the oxidation peaks at +0.37, +0.45, and +0.78 V are assigned to the catechol group in the B-ring of Q3G, the 3-hydroxy group in the C-ring of Q4'G, and the resorcinol group in the A-ring of both Q4'G and Q34'G, respectively. Currents, which are determined by CV, of individual quercetin glucosides at the peak potential are proportional to the concentrations of onion, apple peel, and tartary buckwheat, which show good agreement with those obtained by high-performance liquid chromatography.


Assuntos
Técnicas Eletroquímicas/instrumentação , Eletrodos , Análise de Alimentos/métodos , Glucosídeos/análise , Quercetina/análise , Técnicas Eletroquímicas/métodos , Fagopyrum/química , Análise de Alimentos/instrumentação , Malus/química , Nanotubos de Carbono , Cebolas/química , Oxirredução , Quercetina/análogos & derivados , Quercetina/química , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
10.
Anal Chim Acta ; 1078: 125-134, 2019 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-31358210

RESUMO

We synthesized three kinds of nitrogen-doped nanoporous carbon nanomaterials (represented by N-mC) through a cost-effective method, that is, pyrolysis of plant biomasses (grass, flower, and peanut shells). We further explored their potential as sensitive bioplatforms for electrochemical label-free aptasensors to facilitate the early detection of alpha-fetoprotein (AFP). Chemical structure characterizations revealed that rich functional groups coexisted in as-synthesized N-mC nanomaterials, such as C-C, C-O, C=O, C-N, and COOH. Among the three kinds of N-mC nanomaterials, the one derived from grass (N-mCg) exhibited the lowest carbon defect degree, the highest ID/IG ratio in the Raman spectra, and the largest specific surface area (186.2 m2 g-1). Consequently, N-mCg displayed excellent electrochemical activity and strong affinity toward aptamer strands, further endowing the corresponding aptasensor with sensitive detection ability for AFP. Electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) were used to investigate the whole detection procedure for AFP. The EIS and DPV results showed that the fabricated N-mCg-based aptasensor possessed an extremely low limit of detection of 60.8 and 61.8 fg·mL-1 (s/n = 3), respectively, for detecting AFP within a wide linear range from 0.1 pg mL-1 to 100 ng mL-1. Moreover, the aptasensor displayed acceptable selectivity and applicability, high reproducibility, and excellent stability in serum samples of cancer patients. Therefore, the proposed cost-effective and label-free strategy based on the nitrogen-doped nanoporous carbon derived from plant biomass is a promising approach for the early detection of various tumor markers.


Assuntos
Biomassa , Técnicas Biossensoriais/métodos , Carbono/química , Técnicas Eletroquímicas/métodos , Nanoestruturas/química , alfa-Fetoproteínas/análise , Adolescente , Adulto , Idoso , Aptâmeros de Nucleotídeos/química , Sequência de Bases , Técnicas Biossensoriais/instrumentação , DNA/química , Técnicas Eletroquímicas/instrumentação , Eletrodos , Feminino , Humanos , Limite de Detecção , Masculino , Pessoa de Meia-Idade , Nitrogênio/química , Plantas/química , Porosidade , Reprodutibilidade dos Testes , Adulto Jovem
11.
Anal Chim Acta ; 1078: 16-23, 2019 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-31358214

RESUMO

The adulteration of herbal medicines by dexamethasone or prednisolone is regarded as a serious problem in many communities. Herein, a novel platform for the separation and quantification of both target steroids in herbal medicines based on electrochemical paper-based analytical devices (ePADs) has been created. The ePAD was composed of Whatman SG81 chromatography paper, 3D-printed devices and a commercial screen-printed electrode. Whatman SG81 silica-coated paper was used for the separation of dexamethasone and prednisolone based on the difference in their partition coefficients during the flow of the mobile phase. The optimal mobile phase was composed of 60% ethyl acetate in cyclohexane and required 7 min for separation. The separated steroids on the paper were then quantified by electrochemical detection using differential pulse voltammetry, in which the 3D-printed devices facilitated the measurement. Analytical detection ranges of 10-500 µg mL-1 were obtained for both dexamethasone and prednisolone (r2 = 0.988 and 0.994, respectively). The limits of detection for dexamethasone and prednisolone were 3.59 and 11.98 µg mL-1, respectively, whereas the limits of quantification were 6.00 and 20.02 µg mL-1, respectively. The amounts of both target steroids derived from real herbal medicine samples determined by the proposed method were comparable to those obtained with assays using standard high-performance liquid chromatography. In addition, a simple evaporation step can be used to increase the concentration of the samples before analysis. These ePADs are simple, low-cost, rapid, and very promising for on-site quantitative detection.


Assuntos
Cromatografia em Papel/métodos , Dexametasona/análise , Técnicas Eletroquímicas/métodos , Preparações Farmacêuticas/análise , Preparações de Plantas/análise , Prednisolona/análise , Carbono/química , Cromatografia em Papel/instrumentação , Contaminação de Medicamentos , Técnicas Eletroquímicas/instrumentação , Eletrodos , Limite de Detecção , Papel , Impressão Tridimensional
12.
Anal Chim Acta ; 1078: 161-167, 2019 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-31358215

RESUMO

Sarcosine is a recently identified biomarker for prostate cancer. However, the rapid detection methods for sarcosine are relatively lack because of the low concentration and the presence of complicated interfering substances in serum or urine. In this manuscript, hollow nanospheres of Fe3O4 was synthesized and used as carrier to disperse Pt (Pt) nanoparticles. In order to achieve excellent electron transfer ability, we use polyaniline to coat Pt-Fe3O4 nanoparticles, and pyrolyze the polyaniline to carbon (C). Thus, hollow magnetic Pt-Fe3O4@C nanocomposites with good electron transfer ability are formed. The Pt-Fe3O4@C nanocomposites have high catalytic activity and stability. The nanocomposites were immobilized on glassy carbon electrode (GCE) to construct a nonenzyme hydrogen peroxide (H2O2) sensor (Pt-Fe3O4@C/GCE). We further construct a sensitive sarcosine biosensor by immobilizing sarcosine oxidase (SOx) on the Pt-Fe3O4@C/GCE. The high catalytic activity and good biocompatibility of Pt-Fe3O4@C nanocomposites greatly retained the bioactivity of immobilized SOx, and the prepared sarcosine biosensor has good electrocatalytic performance towards sarcosine. It has a linear detection range between 0.5 and 60 µM with a limit of detection (LOD) of 0.43 µM (the signal to noise ratio is 3), and the sensitivity is 3.45 nA µM-1 (48.8 nA µM-1 cm-2), which has the potential to be used for rapid screening of prostate cancer.


Assuntos
Nanopartículas de Magnetita/química , Nanocompostos/química , Sarcosina/sangue , Técnicas Biossensoriais/instrumentação , Técnicas Biossensoriais/métodos , Carbono/química , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Enzimas Imobilizadas/química , Humanos , Limite de Detecção , Platina/química , Sarcosina Oxidase/química
13.
Anal Chim Acta ; 1078: 24-31, 2019 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-31358225

RESUMO

A novel electrochemical DNA biosensor was developed and MON89788 of soybean transgenic gene sequence was detected based on a strategy of rolling circle amplification (RCA) and gold nanoparticle cube (AuNPC)-labeled multiple probes. First, the mercapto-modified capture DNA was immobilized on the surface of the Fe3O4@Au magnetic nanoparticles via an Au-S bond, and the capture DNA was opened and complementarily hybridized with the target DNA to form a double-stranded DNA. In the 10 × reaction buffer, Exonuclease III (ExoIII) specifically recognized and sheared the double-stranded DNA to release the target DNA, which led to the next round of reaction. Afterward, AuNP cube-loaded ssDNA (AuNPC/DNA) was added with the rolling circle reaction with the help of Phi29 DNA polymerase and T4 ligase. Finally, [Ru(NH3)6]3+ was attracted directly by the anionic phosphate of ssDNA via electrostatic interaction. The determination was carried out by using chronocoulometry (CC), and the CC signal was recorded. The mass amount of DNA strands extended infinitely on the AuNPs cube and numerous [Ru(NH3)6]3+ were absorbed, thus the detected signal was highly amplified. The corresponding CC signal showed a good linear relationship with the logarithm of the target DNA concentration in the range of 1 × 10-16 to 1 × 10-7 mol L-1, with a detection limit of 4.5 × 10-17 mol L-1. Specific gene sequence of MON89788 in soybean samples was determined, and the recoveries ranged from 97.3% to 102.0%. This sensor is one of the most sensitive sensors for genetic sequence assessment at present. Moreover, it demonstrates good selectivity, stability, and reproducibility.


Assuntos
Técnicas Biossensoriais/métodos , DNA de Plantas/análise , Técnicas Eletroquímicas/métodos , Plantas Geneticamente Modificadas/genética , Soja/genética , Sequência de Bases , Calibragem , Sondas de DNA/química , Sondas de DNA/genética , DNA de Plantas/química , DNA de Plantas/genética , Exodesoxirribonucleases/química , Ouro/química , Limite de Detecção , Nanopartículas de Magnetita/química , Técnicas de Amplificação de Ácido Nucleico/métodos , Hibridização de Ácido Nucleico , Oligodesoxirribonucleotídeos/química , Oligodesoxirribonucleotídeos/genética , Reprodutibilidade dos Testes , Compostos de Rutênio/química
14.
Anal Chim Acta ; 1078: 42-52, 2019 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-31358227

RESUMO

Hemoglobin A1c (HbA1c) is a standard biomarker to measure long-term average glucose concentration for diagnosis and monitoring of diabetes. Various methods have been reported for measuring HbA1c, however, portable and precise determination is still challenging. Herein, a new highly sensitive electrochemical nanobiosensor is developed for the specific determination of HbA1c. A nanocomposite of reduced graphene oxide (rGO) and gold with hierarchical architecture structure was electrochemically deposited on a cheap and flexible graphite sheet (GS) electrode. The nanocomposite increased the surface area, improved the electron transfer on the electrode surface and augmented the signal. It also provided a suitable substrate for linkage of thiolated DNA aptamer as a bioreceptor on the electrode surface by strong covalent bonding. The quantitative label free detection was carried out by differential pulse voltammetry (DPV) in a phosphate-buffered saline (PBS) solution containing redox probe Fe(CN)63-/4-. The detection is based on insulating the surface in presence of HbA1c and decreasing the current, which is directly related to the HbA1c concentration. The nanobiosensor demonstrated high sensitivity of 269.2 µA. cm-2, wide linear range of 1 nM-13.83 µM with a low detection limit of 1 nM. The biosensor was successfully used for measuring HbA1c in blood real sample. Furthermore, it is promising to use it as a part of a point of care device for low-invasive screening and management of diabetes.


Assuntos
Técnicas Biossensoriais/métodos , Técnicas Eletroquímicas/métodos , Hemoglobina A Glicada/análise , Grafite/química , Nanopartículas Metálicas/química , Papel , Aptâmeros de Nucleotídeos/química , Aptâmeros de Nucleotídeos/genética , Sequência de Bases , Técnicas Biossensoriais/instrumentação , DNA/química , DNA/genética , Técnicas Eletroquímicas/instrumentação , Eletrodos , Ouro/química , Humanos , Limite de Detecção , Nanocompostos/química , Reprodutibilidade dos Testes
15.
Food Chem ; 300: 125179, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31325751

RESUMO

In this work, a disposable and portable aptasensor for the fast and sensitive detection of oxytetracycline (OTC) using gold nanoparticles (AuNPs)/carboxylated multi-walled carbon nanotubes (cMWCNTs)@thionine connecting complementary strand of aptamer (cDNA) as signal tags was constructed. The substrate electrode of the aptasensor was thin film gold electrode (TFGE), which have the advantages of portable and uniform performance. In the presence of OTC, OTC competed with cDNA to combine with aptamer. The bioconjugate (AuNPs/cMWCNTs/cDNA@thionine) was released from the TFGE. Thus, the electrochemical signal declined. Under optimized conditions, the aptasensor exhibited good stability, high selectivity and high sensitivity. Furthermore, the developed electrochemical aptamer-based TFGE had a wide dynamic range of 1 × 10-13-1 × 10-5 g mL-1 for target OTC with a low detection limit of 3.1 × 10-14 g mL-1 and was successfully used for the determination of OTC in chicken sample.


Assuntos
Técnicas Eletroquímicas/métodos , Eletrodos , Contaminação de Alimentos/análise , Oxitetraciclina/análise , Produtos Avícolas/análise , Animais , Antibacterianos/análise , Aptâmeros de Nucleotídeos , Galinhas , Análise de Alimentos/instrumentação , Análise de Alimentos/métodos , Ouro/química , Limite de Detecção , Nanopartículas Metálicas/química , Nanotubos de Carbono/química , Sensibilidade e Especificidade
16.
Food Chem ; 300: 125178, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31326677

RESUMO

In this work, a sensitive and stable ZrO2-Cu(I) nanosphere mesoporous material modified non-enzymatic glucose sensor has been developed through simple, low cost chemistry. ZrO2-Cu(I) material was obtained by controlled co-precipitation method under ultra dilution conditions. Cyclic voltammetric tests were performed in order to evaluate the electrocatalytic activity ZrO2-Cu(I) modified electrode. The modified electrode showed high sensitivity, wide linear range and very low detection limit of 0.25 mM, this indicates that the modified sensor is competent with that reported earlier. Spherical morphology of the active material, alkaline environment and presence of +1 copper have significantly enhanced the electro-catalytic oxidation of glucose on carbon paste platform. Also, the fabricated electrode showed excellent anti-interference nature. Electro-catalytic oxidation of glucose was demonstrated in real raw unpurified orange juice, this shows the selective electrocatalytic activity of the ZrO2-Cu(I) nanosphere material towards glucose even in the presence of interferrants.


Assuntos
Citrus sinensis/química , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Glucose/análise , Carbono/química , Catálise , Cobre/química , Análise de Alimentos/instrumentação , Análise de Alimentos/métodos , Sucos de Frutas e Vegetais/análise , Glucose/química , Limite de Detecção , Nanosferas/química , Oxirredução , Zircônio/química
17.
J Agric Food Chem ; 67(33): 9187-9202, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31259552

RESUMO

The rationale and scope of the main issues of antioxidant measurement are presented, with basic definitions and terms in antioxidant research (such as reactive species and related antioxidative defenses, oxidative stress, and antioxidant activity and capacity) in a historical background. An overview of technical problems and expectations is given in terms of interpretation of results, precision and comparability of methods, capability of simulating physical reality, and analytical performance (sensitivity, selectivity, etc.). Current analytical methods for measuring antioxidant and antiradical activity are classified from various viewpoints. Reaction kinetics and thermodynamics of current analytical methods are discussed, describing physicochemical aspects of antioxidant action and measurement. Controversies and limitations of the widely used antioxidant assays are elaborated in detail. Emerging techniques in antioxidant testing (e.g., nanotechnology, sensors, electrochemistry, chemometry, and hyphenated methods) are broadly introduced. Finally, hints for the selection of suitable assays (i.e., preferable for a specific purpose) and future prospects are given.


Assuntos
Antioxidantes/química , Técnicas de Química Analítica/métodos , Técnicas Eletroquímicas/métodos , Nanotecnologia/métodos , Espécies Reativas de Oxigênio/química , Oxirredução
18.
19.
Chem Commun (Camb) ; 55(65): 9653-9656, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31342021

RESUMO

The fast and accurate real-time monitoring of hydrogen peroxide (H2O2) secreted from living cells plays a critical role in clinical diagnosis and management. Herein, we report low-cost and self-supported MoS2 nanosheet arrays for non-enzymatic eletrochemical H2O2 detection. Under the optimal test conditions, such MoS2 electrodes exhibit extremely promising electrocatalytic performance with a low detection limit of 1.0 µM (S/N = 3) and an excellent sensitivity of 5.3 mA mM-1 cm-2. Furthermore, the detection of the trace amount of H2O2 secreted from live A549 cancer cells was successfully performed with this biosensor.


Assuntos
Dissulfetos/química , Peróxido de Hidrogênio/análise , Molibdênio/química , Nanoestruturas/química , Células A549 , Técnicas Biossensoriais/métodos , Carbono/química , Dissulfetos/síntese química , Técnicas Eletroquímicas/métodos , Humanos , Limite de Detecção
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