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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
3.
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
4.
Anal Bioanal Chem ; 411(23): 5929-5935, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31338538

RESUMO

Because cerebral species involve rapid events, increasing the temporal resolution to realize in vivo near-real-time measurements is desirable. Here, we aimed to improve the low resolution of our previous on-line electroanalytical system by decreasing the dead volume and reducing molecular dispersion. This updated system has advantages of elevated time resolution and accelerated analysis for on-line monitoring of glucose versus the previous system. Finally, this new system was successfully applied to continuous measurement of cerebral glucose in vivo during global ischemia/reperfusion events. This study is expected to offer a reliable on-line analytical platform for continuous monitoring of important species associated with fast physiological and pathological events in vivo. Graphical abstract.


Assuntos
Encéfalo/metabolismo , Técnicas Eletroquímicas/instrumentação , Glucose/metabolismo , Microdiálise/instrumentação , Animais , Técnicas Biossensoriais/instrumentação , Química Encefálica , Desenho de Equipamento , Glucose/análise , Masculino , Ratos Sprague-Dawley
5.
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
6.
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
7.
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
8.
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
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.
Chemphyschem ; 20(16): 2082-2092, 2019 08 16.
Artigo em Inglês | MEDLINE | ID: mdl-31233266

RESUMO

The studied enzyme-based biocatalytic system mimics NXOR Boolean logic gate, which is a logical operator that corresponds to equality in Boolean algebra. It gives the functional value true (1) if both functional arguments (input signals) have the same logical value (0,0 or 1,1), and false (0) if they are different (0,1 or 1,0). The output signal producing reaction is catalyzed by pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH), which is inhibited at acidic and basic pH values. Two other reactions catalyzed by esterase and urease produce acetic acid and ammonium hydroxide, respectively, shifting solution pH from the optimum pH for PQQ-GDH to acidic and basic values (1,0 and 0,1 input combinations, respectively), thus switching the enzyme activity off (output 0). When the input signals are not applied (0,0 combination) or both applied compensating each other (1,1 combination) the optimum pH is preserved, thus keeping PQQ-GDH running at the high rate (output 1). The biocatalytic cascade mimicking the NXOR gate was characterized optically and electrochemically. In the electrochemical experiments the PQQ-GDH enzyme communicated electronically with a conducting electrode support, thus resulting in the electrocatalytic current when signal combinations 0,0 and 1,1 were applied. The logic gate operation, when it was realized electrochemically, was also extended to the biomolecular release controlled by the gate. The release system included two electrodes, one performing the NXOR gate and another one activated for the release upon electrochemically stimulated alginate hydrogel dissolution. The studied system represents a general approach to the biocatalytic realization of the NXOR logic gate, which can be included in different catalytic cascades mimicking operation of concatenated gates in sophisticated logic circuitries.


Assuntos
Computadores Moleculares , Esterases/química , Glucose Desidrogenase/química , Lógica , Urease/química , Acetatos/química , Alginatos/química , Animais , Canavalia/enzimologia , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Fluoresceína-5-Isotiocianato/química , Corantes Fluorescentes/química , Concentração de Íons de Hidrogênio , Ferro/química , Nanotubos de Carbono/química , Suínos , Ureia/química
12.
Chem Commun (Camb) ; 55(60): 8840-8843, 2019 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-31168558

RESUMO

Redox reactions and paramagnetic intermediates are ubiquitous in biological chemistry. We report a new method, protein film electrochemical electron paramagnetic resonance spectroscopy (PFE-EPR), that enables the direct and accurate potential control of proteins on the electrode surface for both electrochemical and EPR spectroscopic characterisation of their redox centres.


Assuntos
Óxidos N-Cíclicos/química , Técnicas Eletroquímicas/métodos , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Superóxido Dismutase-1/química , Animais , Bovinos , Técnicas Eletroquímicas/instrumentação , Eletrodos , Oxirredução
13.
Anal Chim Acta ; 1074: 131-141, 2019 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-31159933

RESUMO

Semiconducting single-walled carbon nanotubes (s-SWCNTs) have been demonstrated as an excellent material for transistors, miniaturized devices and sensors due to their high carrier mobility, stability, scattering-free ballistic transport of carriers etc. Herein, we have designed a biosensor to selectively detect methyl parathion (MP, organophosphorus pesticide) using glutaraldehyde (Glu) cross-linked with acetylcholinesterase (AChE) immobilized on s-SWCNTs wrapped with bovine serum albumin (BSA). The fabricated biosensor was characterized and confirmed by Fourier-transform infrared spectroscopy (FT-IR), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV). In the presence of MP, the effective interaction between AChE and MP favours the accumulation of MP-AChE complex on the glassy carbon electrode (GCE) surface which reduces the electron transfer property. Based on this interaction, detection of various concentration of MP was demonstrated by SWV using BSA/AChE-Glu-s-SWCNTs composite modified electrode. The proposed biosensor exhibited a wide linear range (WLR) for MP target in 100 mM phosphate buffered saline solution (PBS) (pH 7.4) from 1 × 10-10 M to 5 × 10-6 M with a limit of detection (LOD) of 3.75 × 10-11 M. In addition, the BSA/AChE-Glu-s-SWCNTs/GCE biosensor showed good repeatability and reproducibility for MP detection. Moreover, the proposed biosensor showed better electrode stability when stored at 4 °C. This new electrochemical biosensor is also exhibited high selectivity and sensitivity for MP, which made it possible to test MP in real strawberry and apple juices. Furthermore, the BSA/AChE-Glu-s-SWCNTs/GCE offered a favourable electron transfer between the acetylthiocholine chloride (ATCl) and electrode interface than BSA/AChE-s-SWCNTs/GCE, s-SWCNTs/GCE and bare GCE.


Assuntos
Acetilcolinesterase/química , Inseticidas/análise , Metil Paration/análise , Nanocompostos/química , Nanotubos de Carbono/química , Soroalbumina Bovina/química , Animais , Técnicas Biossensoriais/métodos , Carbono , Bovinos , Reagentes para Ligações Cruzadas/química , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Electrophorus , Enzimas Imobilizadas/química , Contaminação de Alimentos/análise , Fragaria/química , Glutaral/química , Inseticidas/química , Limite de Detecção , Malus/química , Metil Paration/química , Reprodutibilidade dos Testes
14.
Anal Chim Acta ; 1074: 89-97, 2019 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-31159943

RESUMO

This work describes the development of a paper-based platform for highly sensitive detection of diclofenac. The quantification of this anti-inflammatory drug is of importance in clinical (e.g. quality and therapeutic control) and environmental (e.g. emerging contaminant determination) areas. The easy-to-handle platform here described consists of a carbon-ink paper-based working electrode and two metallic wires, provided by a gold-plated standard connector, as reference and counter electrodes. The porous paper matrix enables the preconcentration of the sample, decoupling sample and detection solutions. Thus, relatively large sample volumes can be used, which significantly improves the sensitivity of the method. A wide dynamic range of four orders of magnitude, between 0.10 and 100 µM, was obtained for diclofenac determination. Due to the predominance of adsorption at the lowest concentrations, there were two linear concentration ranges: one comprised between 0.10 and 5.0 µM (with a slope of 0.85 µA µM-1) and the other between 5.0 and 100 µM (with a slope of 0.48 µA µM-1). A limit of detection of 70 nM was achieved with this simple device that provided accurate results with an RSD of ca. 5%. The platform was applied for diclofenac quantification in spiked tap water samples. The versatility of this design enabled the fabrication of a multiplexed platform containing eight electrochemical cells that work independently. The low cost, small size and simplicity of the device allow on-site analysis, which is very useful for environmental monitoring.


Assuntos
Anti-Inflamatórios/análise , Diclofenaco/análise , Papel , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Desenho de Equipamento , Limite de Detecção , Nanotubos de Carbono
15.
Anal Chim Acta ; 1074: 80-88, 2019 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-31159942

RESUMO

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


Assuntos
Proteínas de Bactérias/genética , Técnicas de Tipagem Bacteriana/métodos , Grafite/química , Nanopartículas Metálicas/química , Polímeros/química , Pirróis/química , Salmonella/isolamento & purificação , Técnicas Biossensoriais/métodos , Carbono , DNA Bacteriano/genética , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Enzimas Imobilizadas/química , Ouro/química , Peroxidase do Rábano Silvestre/química , Peróxido de Hidrogênio/química , Hidroquinonas/química , Limite de Detecção , Nanocompostos/química , Hibridização de Ácido Nucleico , Oxirredução , Salmonella/genética , Estreptavidina/química
16.
Food Chem ; 297: 124968, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31253322

RESUMO

A novel electrochemical sensor was developed combination molecularly imprinted polymers (MIPs) with nanowell technology, and which was utilized for sensitive and selective 17ß-estradiol (17ß-E2) detection. A nanowell gold film with a thickness of 120 nm and a pore size of ∼20 nm was immobilized onto gold electrode surface to form a nanowell-based electrode. MIPs was then synthesized onto the nanowell-based electrode using electro-polymerization method, and then the nanowell-based MIP electrochemical sensor was formed. This sensor surface exhibited 3D-nanowell structure with higher surface area and enhanced electron-transport ability, while MIPs afford stronger recognition capability with higher selectivity and specificity. Most importantly, the developed sensor was validated for 17ß-E2 detection in food samples with larger detection range from 1 × 10-12 to 1 × 10-5 and lower detection limit of 1 × 10-13. Therefore, such nanowell-based MIP electrochemical sensor may be a promising candidate electrochemical sensor for trace pollution detection in food samples.


Assuntos
Técnicas Eletroquímicas/instrumentação , Estradiol/análise , Análise de Alimentos/métodos , Impressão Molecular/métodos , Nanoestruturas/química , Técnicas Eletroquímicas/métodos , Eletrodos , Análise de Alimentos/instrumentação , Contaminação de Alimentos/análise , Ouro/química , Limite de Detecção , Polimerização , Polímeros/química , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
17.
Anal Chim Acta ; 1075: 120-127, 2019 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-31196417

RESUMO

In situ identification and quantification of unsaturated fatty acid (FA) C=C positional isomers in human serum is herein performed by negative-ion paper spray (PS) mass spectrometry. Typically, by direct application of an alternating current (AC) voltage to the wet paper, the PS ionization could perform stably in the negative-ion mode without severe discharge. We suppose epoxidation reaction between unsaturated C=C bonds and reactive oxidative species might be initiated by a mild electrical discharge, which could be rapidly and controllably produced via a low amplitude AC voltage. Upon collision-induce dissociation (CID), the epoxide was fragmented to generate diagnostic ions indicating the C=C location. The intensity of the characteristic product ions could also be used for absolute quantification of the FA C=C positional isomers. The limits of detection (LODs) and limits of quantification (LOQs) were roughly in the range of 0.0178-0.0506 µM and 0.0218-0.3634 µM for standard FAs. Without the additional sample preparations or reactive chemical reagents, epoxidation of unsaturated FAs and ionization of the epoxide could be achieved in one-step by negative-ion mode PS, which enable a promising methodology for on-site clinical diagnosis.


Assuntos
Ácidos Graxos Insaturados/sangue , Fontes de Energia Elétrica , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Compostos de Epóxi/síntese química , Desenho de Equipamento , Ácidos Graxos Insaturados/química , Humanos , Limite de Detecção , Papel , Reprodutibilidade dos Testes , Espectrometria de Massas por Ionização por Electrospray/instrumentação , Espectrometria de Massas por Ionização por Electrospray/métodos
18.
Anal Chim Acta ; 1075: 91-97, 2019 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-31196427

RESUMO

Antioxidants are important to protect and maintain biological barriers, such as the skin. Antioxidant effects are often assessed using clinical trials, however these tests are costly and time consuming. In this work we introduce a skin membrane-covered oxygen electrode (SCOE) as an in vitro tool for monitoring H2O2 and antioxidant reactions in skin. The SCOE gives amperometric response to H2O2 concentrations down to 0.05 mM. More importantly, the electrode allows measurements of polyphenol penetration and reaction with H2O2 in skin. Measurements with SCOE show that lipophilic polyphenols such as quercetin, piceatannol, resveratrol, and plant extract from Plantago major impose their antioxidant effect in skin within 2-20 min. Rutin is however too hydrophilic to penetrate into stratum corneum and therefore cannot deliver its antioxidant effect during similar time interval. The measurements are interpreted considering polyphenol partition-penetration through stratum corneum and the reaction with the H2O2-catalase system in the skin. The contribution of other enzymes will be addressed in the future.


Assuntos
Antioxidantes/metabolismo , Peróxido de Hidrogênio/análise , Inflamação/metabolismo , Polifenóis/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Pele/metabolismo , Animais , Técnicas Biossensoriais/instrumentação , Técnicas Biossensoriais/métodos , Catalase/metabolismo , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Peróxido de Hidrogênio/metabolismo , Hidroquinonas/metabolismo , Limite de Detecção , Oxigênio/química , Extratos Vegetais/química , Plantago/química , Pele/enzimologia , Suínos
19.
Analyst ; 144(13): 4073-4080, 2019 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-31165805

RESUMO

Ratiometric electrochemical sensors can provide a relatively accurate analysis of target analytes due to their self-calibration function. Herein, we report a simple ratiometric strategy for achieving the electrochemical detection of Cd(ii), Hg(ii), Pb(ii) and Zn(ii), as well as multiple cancer biomarkers by using metal sulfide nanoparticles as signal tags. A conductive polymer film of poly(2-amino terephthalic acid) (ATA) was electrochemically produced on a glassy carbon electrode (GCE) and doped with carbon nanotubes (CNTs) and mercaptosuccinic acid (MSA). Using Bi(iii) as an enhancer and internal reference in anodic stripping voltammetry, the MSA-CNT-ATA/GCE exhibited sensitive and distinguishable voltammetric responses to Cd(ii), Hg(ii), Pb(ii) and Zn(ii), with detection limits of 0.13, 0.49, 0.16 and 0.089 µg L-1, respectively. By using CdS, HgS, PbS and ZnS labeled secondary antibodies as the signal tags, alpha-fetoprotein, carbohydrate antigen 19-9, carbohydrate antigen 125, and carcinoembryonic antigen were determined simultaneously according to the amounts of metal sulfide in the sandwich-type complexes, with detection limits of 0.11 pg mL-1, 0.68 mU mL-1, 1.4 mU mL-1 and 0.23 pg mL-1, respectively. This ratiometric approach has a wide scope in the electrochemical detection of heavy metal ions as well as immunoassays with metal ions serving as signal tags.


Assuntos
Biomarcadores Tumorais/sangue , Bismuto/química , Nanopartículas Metálicas/química , Metais Pesados/análise , Sulfetos/química , Anticorpos/imunologia , Biomarcadores Tumorais/imunologia , Antígeno Ca-125/sangue , Antígeno Ca-125/imunologia , Antígeno CA-19-9/sangue , Antígeno CA-19-9/imunologia , Antígeno Carcinoembrionário/sangue , Antígeno Carcinoembrionário/imunologia , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Imunoensaio/métodos , Limite de Detecção , Proteínas de Membrana/sangue , Proteínas de Membrana/imunologia , Metais Pesados/química , Nanotubos de Carbono/química , Ácidos Ftálicos/química , Polímeros/química , Reprodutibilidade dos Testes , alfa-Fetoproteínas/análise , alfa-Fetoproteínas/imunologia
20.
Anal Chim Acta ; 1076: 55-63, 2019 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-31203964

RESUMO

In this work, an implantable and minimally invasive micro-aptasensor for adenosine monitoring in vivo, based on flexible integrated electrodes, was developed. Firstly the sensor was made by the modification of a needle-type electrode with reduced graphene oxide and gold nanoclusters (rGO-AuNCs) using two-step electrodeposition. Secondly Sulfhydryl-terminated capture probe (ssDNA1) was immobilized on rGO-AuNCs modified electrode surface by self-assembly, and then it was hybridized with adenosine aptamer (ssDNA2). Lastly methylene blue (MB) as an electrochemical indicator was adsorbed on the aptamer through specific interaction of MB with guanine base. The peak current of MB decreased linearly with increasing adenosine concentration due to the formation of aptamer-adenosine complex and displacement of the aptamer from the modified electrode surface. The sensor showed a low detection limit of 0.1 nM with signal-to-noise ratio equal to 3 as well as a wide linear response range (0.1 nM-1 mM) in vitro. Also, a high selectivity was demonstrated for adenosine in relation to uridine, guanosine, and cytidine. Experiments in vivo demonstrated fast responses for a range of adenosine concentrations. This work demonstrates a promising path for implantable devices for the determination of biomolecules in vivo, thus allowing for health tests, detection of infectious diseases, and other medical conditions.


Assuntos
Adenosina/análise , Aptâmeros de Nucleotídeos/química , DNA/química , Animais , Aptâmeros de Nucleotídeos/genética , Técnicas Biossensoriais/instrumentação , Técnicas Biossensoriais/métodos , DNA/genética , Sondas de DNA/química , Sondas de DNA/genética , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Ouro/química , Grafite/química , Indicadores e Reagentes/química , Limite de Detecção , Masculino , Nanopartículas Metálicas/química , Azul de Metileno/química , Hibridização de Ácido Nucleico , Ratos Wistar
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