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1.
Talanta ; 233: 122527, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34215030

RESUMO

Dengue is one of the most commonly neglected tropical diseases transmitted by Aedes aegypti infected with Dengue virus. This virus belongs to the gender Flavivirus and produces a non-structural protein 1 (NS1), which is an important biomarker found at high levels in blood in early disease stage. Therefore, this study focused on the development of an electrochemical biosensor for NS1 detection using DNA aptamers. Gold electrodes were co-immobilized with specific aptamers and 6-mercapto-1-hexanol (MCH) to obtain a self-assembled monolayer. The molar ratio between aptamers and MCH was optimized and the platform characterized by electrochemical impedance spectroscopy and atomic force microscopy. Bovine serum albumin was added in NS1 solution to stabilize it and block the surface to avoid non-specific interactions. The biosensor performance was tested with NS1 protein serotype 4 (in phosphate saline buffer and human serum) and with a solution of serotype 1 in human serum. The results showed a sensitivity of 2.9%, 2.7% and 1.7% per decade, respectively, and low limit of detection (0.05, 0.022 and 0.025 ng/mL). The platform was also tested with Envelope protein as negative control. Furthermore, the aptamer sensor was able to detect NS1 in clinical range and it is a promising candidate for a new class for miniaturized point-of-care device for different Dengue serotypes.


Assuntos
Aptâmeros de Nucleotídeos , Técnicas Biossensoriais , Dengue , Dengue/diagnóstico , Espectroscopia Dielétrica , Eletrodos , Humanos , Limite de Detecção
2.
Talanta ; 233: 122539, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34215042

RESUMO

An amperometric sensor has been developed with high sensitivity for real-time measurement of H2S gas at room temperature (25 °C ± 2 °C). In order to enhance the utilization of platinum and improve its catalytic performance, an ultrathin and one-dimensional (1D) Pt nanotubes (Pt NTs, ~3.5 nm in wall thickness) were designed and used as sensing electrode materials. Different concentrations of H2S gas were tested to evaluate the sensitivity of the sensor and to obtain the relationship between the electricity response signal and H2S gas concentration. At room temperature, the sensor based on Pt NTs shows better sensing performance than that based on Pt nanoparticles, which is mainly attributed to two factors, namely, the inherent characteristic of the hollow 1D Pt NTs. The Pt NTs-based sensor shows a detection limit as low as 0.025 ppb, which are the lowest among H2S gas sensors reported in the literatures. The response and recovery times are 0.75 s and 0.86 s for 0.8 ppb H2S, respectively. In addition, the sensor shows a wide range (100 ppm-0.025 ppb), high selectivity compared to other gases (including CO, NH3, CH2O, NO and NO2), good reproducibility, and satisfactory long-term stability. Thus, the ultrathin Pt NTs-based gas sensor would be a great potential to the real-time and online monitoring of the trace ppb-level H2S gas at room temperature.


Assuntos
Nanotubos , Eletrodos , Gases , Platina , Reprodutibilidade dos Testes
3.
Talanta ; 233: 122545, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34215048

RESUMO

A nanocomposite of ordered mesoporous carbon/nickel oxide (OMC-NiO) was synthesized by hard-templating method. The nanocomposite remained ordered mesostructure and high surface area with the NiO nanocrystals embedded in the wall of the OMC. A sensitive sensor for electrochemical detection of epinephrine (EP) was developed with GCE modified by OMC-NiO nanocomposite. Cyclic voltammogram (CV) and differential pulse voltammetry (DPV) were used as the techniques to explore the electrochemical behavior of EP on OMC-NiO/GCE surface. The result showed that the electrode demonstrated better electrocatalytic performance to EP compared to that seen at OMC/GCE. Under the optimum condition, DPV measurements of the electrode response displayed a linear detection range for 8.0 × 10-7 to 5.0 × 10-5 M with a detection limit of 8.5 × 10-8 M (S/N = 3). It is worth noting that the electrocatalytic redox mechanism of EP on the electrode have studied through experiments and calculations (cyclic voltammetry and molecular electrostatic potential distribution). Moreover, the electrocatalytic behavior for the oxidation of EP and uric acid (UA) on OMC-NiO/GCE surface was investigated. The result showed that the sensor can be used to selectively determinate EP in the presence of an excesses of UA. Finally, the developed sensor was successfully applied to the determination of EP in spiked human blood serum and EP injection with satisfactory results.


Assuntos
Carbono , Nanocompostos , Técnicas Eletroquímicas , Eletrodos , Epinefrina , Humanos , Níquel
4.
Talanta ; 233: 122565, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34215061

RESUMO

This work presents a new fast and sensitive method for voltammetric determination of Al(III) as Al(III)-cupferron complexes, which was used for the analysis of solution after exposure of aluminum alloy AA2024. Experimental conditions of voltammetric measurement such as preconcentration time, potential, and operating parameters were optimized. The formed Al(III)-cupferron complexes were adsorbed on an in situ plated lead film electrode (PbFE) using the potentials of -1.2 V (15 s) and -0.7 V (60 s) versus Ag/AgCl electrode. The promising results were obtained in 0.1 mol L-1 ammonia buffer at pH = 8.15 and 6 ∙ 10-5 mol L-1 Pb(II), 3 ∙ 10-4 mol L-1cupferron. The calibration graph was linear from 1 ∙ 10-10 to 2 ∙ 10-7 mol L-1 with the calculated detection limit of 3.3 ∙ 10-11 mol L-1, repeatability with RSD of 4.9% (n = 5). The accuracy was established by analysis of the synthetic sample.


Assuntos
Alumínio , Adsorção , Corrosão , Eletroquímica , Eletrodos
5.
Talanta ; 233: 122569, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34215065

RESUMO

In this study, a novel, fast, selective, and sensitive molecularly imprinted polymer (MIP)-based electrochemical sensor was developed to determine axitinib (AXI) at low concentrations in pharmaceutical dosage forms and human serum. The newly developed MIP-based sensor (MIP@o-PD/GCE) was designed through electropolymerization of functional monomer o-phenylenediamine (o-PD) in the presence of a template molecule AXI, on a glassy carbon electrode (GCE) using cyclic voltammetry. Differential pulse voltammetry and electrochemical impedance spectroscopy (EIS) techniques were employed for removal and rebinding processes, optimization of conditions, as well as for performance evaluation of MIP@o-PD/GCE using [Fe(CN)6]3-/4- as the redox probe. Under the optimum experimental conditions, MIP@o-PD/GCE shows a linear response toward AXI in a range of 1 × 10-13 M - 1 × 10-12 M. The limit of the detection value of MIP@o-PD/GCE was found as 0.027 pM while the limit of the quantification was obtained as 0.089 pM, respectively. To demonstrate the applicability and validity of the developed sensor, it was successfully applied to tablet dosage form and human serum sample. The selectivity of the sensor was qualified by comparing the binding of AXI, erlotinib, dasatinib, nilotinib, and imatinib, which are similarly structured and in the same group of anticancer drugs. MIP@o-PD/GCE sensor showed a significant selectivity toward AXI. The non-imprinted polymer (NIP) based GCE was prepared and used to control the analytical performance of the MIP-based electrochemical sensor.


Assuntos
Antineoplásicos , Impressão Molecular , Axitinibe , Técnicas Eletroquímicas , Eletrodos , Humanos , Limite de Detecção
6.
Talanta ; 233: 122571, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34215067

RESUMO

Single-cell analysis has gained considerable attention for disease diagnosis, drug screening, and differentiation monitoring. Compared to the well-established flow cytometry, which uses fluorescent-labeled antibodies, microfluidic impedance cytometry (MIC) offers a simple, label-free, and noninvasive method for counting, classifying, and monitoring cells. Superior features including a small footprint, low reagent consumption, and ease of use have also been reported. The MIC device detects changes in the impedance signal caused by cells passing through the sensing/electric field zone, which can extract information regarding the size, shape, and dielectric properties of these cells. According to recent studies, electrode configuration has a remarkable effect on detection accuracy, sensitivity, and throughput. With the improvement in microfabrication technology, various electrode configurations have been reported for improving detection accuracy and throughput. However, the various electrode configurations of MIC devices have not been reviewed. In this review, the theoretical background of the impedance technique for single-cell analysis is introduced. Then, two-dimensional, three-dimensional, and liquid electrode configurations are discussed separately; their sensing mechanisms, fabrication processes, advantages, disadvantages, and applications are also described in detail. Finally, the current limitations and future perspectives of these electrode configurations are summarized. The main aim of this review is to offer a guide for researchers on the ongoing advancement in electrode configuration designs.


Assuntos
Técnicas Analíticas Microfluídicas , Microfluídica , Impedância Elétrica , Eletrodos , Citometria de Fluxo , Dispositivos Lab-On-A-Chip
7.
Talanta ; 233: 122596, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34215084

RESUMO

Detection of explosives at trace levels is crucial for security purposes because of increasing worldwide terrorist threats at public places. Previously, a hollow cathode discharge (HCD) ion source has been fabricated for detection of explosives. Recently, the HCD ion source has been modified for a dual pressures operating system and coupled to a linear ion trap MS to analyze explosives simultaneously. Here, trinitrotoluene (TNT), nitroglycerin (NG), pentaerythritol tetranitrate (PETN) and 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) were taken as model explosive compounds and the mass spectra were recorded in the negative mode ionization. At the higher ion source pressure (~28.0-30.0 Torr), NG, PETN and RDX gave adduct ions with the NO3- ion while TNT showed the [TNT + NO3-HNO2]- (m/z 242) simultaneously. However, NG and PETN did not give any ion signals at the lower ion source pressure (~0.8-1.0 Torr) while TNT exhibited its molecular ion, [TNT]-• (m/z 227), as a major ion through electron attachment and RDX showed fragment ions that followed electron capture dissociation concurrently. The modified HCD ion source exhibited better sensitivity in simultaneous detection and quantification of the explosives. The NO3- and NO2- as reagent ions in the air HCD plasma form stable adduct ions with the NG, PETN and RDX even with TNT at the higher temperature (140-200 °C). The formation of the NO3-, NO2- in the HCD plasma also causes the formation of [TNT-H]- (m/z 226) at the higher ion source pressure. The inner metallic surface of the hollow tube assists the Birch reduction type reaction that results in the formation of hydride ion of the TNT, [TNT + H]- (m/z 228). No significant difference in the spectral pattern for simultaneous and individual measurements for the explosives was observed at the higher ion source pressure. Therefore, it may conclude that the present modified HCD ion source can be used for simultaneous detection and quantification of the explosive compounds at trace and/or ultra-trace levels using air as a carrier gas.


Assuntos
Substâncias Explosivas , Tetranitrato de Pentaeritritol , Trinitrotolueno , Eletrodos , Humanos , Alta do Paciente
8.
Talanta ; 233: 122597, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34215085

RESUMO

1-(3-chlorophenyl) piperazine (mCPP) is a synthetic drug with hallucinogenic effects that has often been found in seized samples. In this context, easy to use point-of-care tests can be of great value in preliminary forensic analysis. Herein, we proposed a simple, fast, and portable electrochemical method for the detection of mCPP in seized samples. The method is based on the use of disposable screen-printed carbon electrodes (SPCE) and rapid screening procedures by square-wave voltammetry using minimal sample sizes (100 µL). mCPP showed an irreversible electrochemical oxidation process at +0.65 V on SPCE (vs Ag) using 0.04 mol L-1 Britton Robinson (BR) buffer solution (pH 7) as the supporting electrolyte. The proposed method exhibited a linear correlation (r = 0.998) between peak current and mCPP concentration in the range of 1-30 µmol L-1 (LOD = 0.1 µmol L-1). Interference studies were performed for adulterants and other classes of drugs of abuse, which can also be found in seized samples containing mCPP, such as caffeine, amphetamine, methamphetamine, 1-benzylpiperazine, 3,4-methylenedioxymethamphetamine, methylone, mephedrone, ethylone and 3, 4-methylenedioxypyrovalerone. The developed method presents great potential as a rapid and simple screening tool to detect mCPP in forensic samples.


Assuntos
N-Metil-3,4-Metilenodioxianfetamina , Anfetaminas , Eletrodos , Piperazinas
9.
Talanta ; 233: 122500, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34215117

RESUMO

As a biomarker of several diseases, the activity of acid phosphatase (ACP) is generally used to assistantly diagnose these diseases. Thus, developing reliable ACP activity analytical methods becomes quite significant. Herein, we recommend a one-step sampling filtration-free electrochemical method for ACP activity determination based on the target-induced synergetic modulation of tag concentration and surface passivation. Mn3O4 microspheres with favorable oxidase-mimicking activity are synthesized to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to its product TMBox, resulting in a remarkable re-reduction signal of TMBox to TMB recorded by an integrated electrochemical system consisting of screen-printed electrode (SPE) and 3D-printed holder. When hexametaphosphate ions (HMPi) with rich negative charges are employed to interact positively charged TMBox, the formed flocculent precipitate TMBox-HMPi automatically sedimentates onto SPE surface, and both the decreased concentration of free TMBox in solution and the increased electrode surface passivation triggered by TMBox-HMPi sedimentation synergistically reduce the re-reduction signal of TMBox. When ACP is present, it hydrolyzes the HMPi substrate, greatly relieving the formation of the TMBox-HMPi precipitate and its sedimentation onto SPE surface. As a result, the electrochemical re-reduction signal of TMBox becomes remarkable again. With the strategy of using one stimulus to generate two-fold signal change, highly sensitive ACP activity detection was realized, with a wide linear range from 0.05 to 50 U/L and a limit of detection down to 0.024 U/L. Reliable monitoring of ACP activity in clinical serum was also demonstrated.


Assuntos
Técnicas Biossensoriais , Colorimetria , Fosfatase Ácida , Catálise , Técnicas Eletroquímicas , Eletrodos , Limite de Detecção , Oxirredução
10.
Talanta ; 233: 122506, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34215121

RESUMO

Early diagnosis of cancer is crucial for therapeutic methods to be more effective and to decrease the mortality rate due to this disease. Current diagnostic methods include imaging techniques that require expensive equipment and specialized personnel, making it difficult to apply them to many patients. To overcome these limitations, many biosensors have been developed to monitor cancer biomarkers. Here, we report on the electrochemical biosensor for selective detection of tumor cells using a simple and low-cost methodology. Layer-by-layer (LbL) self-assembly was used to modify indium tin oxide (ITO) electrodes with alternating layers of polyallylamine hydrochloride (PAH) and folic acid (FA), which binds to overexpressed folate receptors alpha (FRα) in tumor cells. The LbL-based biosensor showed high sensitivity in detecting cervical cancer cells (HeLa cells) using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). A linear dependence with the logarithm cell concentration was observed and excellent detection limits were found, 4 cells mL-1 and 19 cells mL-1 for EIS and CV measurements, respectively. The developed biosensor also presented great reproducibility (RSD = 1.7%) and repeatability (RSD = 1.8%). The selectivity was confirmed after the biosensor interaction with healthy cells (HMEC cells), which did not produce significant changes in the electrochemical signals. Furthermore, it was demonstrated that selective detection of tumor cells occurs via an interaction with FA. The LbL-based biosensor provides a simple, accurate, and cost-effective platform to be applied in the early diagnosis of cancer.


Assuntos
Técnicas Biossensoriais , Neoplasias , Técnicas Eletroquímicas , Eletrodos , Células HeLa , Humanos , Neoplasias/diagnóstico , Reprodutibilidade dos Testes
11.
Anal Chim Acta ; 1174: 338736, 2021 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-34247730

RESUMO

The constant need of humans and animals for food resources was led to overuse of antibiotics as vital medicines. In this regard, we are now facing major concern about the risks on the food safety and environment owing to their uncontrolled disposal. Hence, the progress of simple and sensitive approaches for fast monitoring of antibiotic levels is highly desirable. Here, we aimed to describe a new sensitive and easy-to use strategy based on electrochemical single off apta-assay toward ciprofloxacin (CFX). A novel interface using 3D Au-PAMAM/rGO have been designed via full electrochemically technique on the surface of glassy carbon electrodes (GCE) and evaluated with cyclic voltammetry method. Firstly, rGO with large amount of active functional groups as substrate was fabricated on the GCE electrode. Thereby, the 3D Au-PAMAM nanocomposite was synthesized and covalently electrodeposited onto the rGO-GCE modified surface. The structure and morphology of 3D Au-PAMAM were studied using UV-Vis spectroscopy, Field emission scanning electron microscopes (FE-SEM) and Transmission electron microscopy. Also, FE-SEM and Energy-dispersive X-ray spectroscopy (EDS) have been carry out to illustrate surface morphology of electrodes. The obtained results from square wave voltammetry, different pulse voltammetry, and chronoamperometry techniques implied that the suggested scaffold could be used as facile bio-device toward antibiotic detection with low limit of quantification (LLOQ) of 1 nM and a linear range of 1 µM-1 nM. Interestingly, the suggested aptasensor is successfully used to measure CFX residues in local and pasteurized milk samples. It can be deduced that Apt/rGO/3D Au-PAMAM/GCE as a novel biocompatible interface could offer suitable, cost-effective, reliable, rapid, and user-friendly sensing device for direct determination of CFX in real samples.


Assuntos
Dendrímeros , Grafite , Animais , Antibacterianos , Ciprofloxacina , Técnicas Eletroquímicas , Eletrodos , Humanos , Leite , Poliaminas
12.
Analyst ; 146(14): 4473-4479, 2021 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-34227625

RESUMO

Electrochemical detection is the simplest analytical tool to be integrated into digital microfluidics (DMF). It offers the advantages of small size, with detector electrodes incorporated into the device by patterning, and high compatibility with portable analytical instruments. Indium tin oxide (ITO) coated on glass has been commonly used for the top plate of DMF due to its good conductivity and transparency. However, instability and the low current response of ITO electrodes patterned on glass hindered their application for immunoassays. It has been reported that ITO coated on polyethylene terephthalate (PET) has better conductivity, owing to its higher carrier concentration, faster mobility and lower resistivity. Herein, we investigated the use of ITO electrodes patterned on PET film as the top plate of DMF for a simple and stable electrochemical immunoassay using square wave voltammetry (SWV), with an excellent peak resolution and high sensitivity. A magnetic bead-based immunoassay for H5N1 antigen was performed on a DMF platform with a limit of detection of 0.6 ng mL-1 in buffer and 18 ng mL-1 in human serum. These results showed the good electrochemical performance of ITO coated on a PET film, a lightweight, shock resistant and cost-effective material, which is promising for DMF fabrication and transparent electrodes for various electroanalytical methods.


Assuntos
Virus da Influenza A Subtipo H5N1 , Polietilenotereftalatos , Eletrodos , Humanos , Imunoensaio , Microfluídica , Compostos de Estanho
13.
Biosens Bioelectron ; 190: 113464, 2021 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-34197998

RESUMO

Microbial electrosynthesis is a promising electricity-driven technology for converting carbon dioxide into value-added compounds, but the formation of cathodic electroactive-biofilms (CEBs) is challenging. Herein, we have demonstrated an innovative strategy for CEBs assembly via magnetic nanoparticle bioconjugation, which lies in the synergistic interactions among a bonder (Streptavidin, SA), conductive nanomaterials (Fe3O4), and a methanogen (M. barkeri). The results showed that the bioconjugated M. barkeri-SA-Fe3O4 biohybrids significantly enhanced both methane yield (33.2-fold) and faradaic efficiency (5.6-fold), compared with that of bare M. barkeri. Such an enhancement was attributed to the improved viability of CEBs with a higher biomass density. Particularly, more live cells were presented in the inner biofilms and promoted the long-distance electron exchange between the live outer-layer biofilm and the cathode electrode. Meanwhile, the higher redox activity of CEBs with the M. barkeri-SA-Fe3O4 biohybrids resulted in an improved transient charge storage capability, which was beneficial for the biological CO2-to-CH4 conversion via acting as an additional electron donor. This work has provided a new approach to accelerate the formation of CEBs and subsequent electron transfer, which holds a great potential for accomplishing electrosynthesis and CO2 fixation.


Assuntos
Técnicas Biossensoriais , Nanopartículas de Magnetita , Biofilmes , Dióxido de Carbono , Eletrodos , Metano
14.
Biosensors (Basel) ; 11(6)2021 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-34200338

RESUMO

The detection of cancer antigens is a major aim of cancer research in order to develop better patient management through early disease detection. Many cancers including prostate, lung, and ovarian secrete a protein disulfide isomerase protein named AGR2 that has been previously detected in urine and plasma using mass spectrometry. Here we determine whether a previously developed monoclonal antibody targeting AGR2 can be adapted from an indirect two-site ELISA format into a direct detector using solid-phase printed gold electrodes. The screen-printed gold electrode was surface functionalized with the anti-AGR2 specific monoclonal antibody. The interaction of the recombinant AGR2 protein and the anti-AGR2 monoclonal antibody functionalized electrode changed its electrochemical impedance spectra. Nyquist diagrams were obtained after incubation in an increasing concentration of purified AGR2 protein with a range of concentrations from 0.01 fg/mL to 10 fg/mL. In addition, detection of the AGR2 antigen can be achieved from cell lysates in medium or artificial buffer. These data highlight the utility of an AGR2-specific monoclonal antibody that can be functionalized onto a gold printed electrode for a one-step capture and quantitation of the target antigen. These platforms have the potential for supporting methodologies using more complex bodily fluids including plasma and urine for improved cancer diagnostics.


Assuntos
Técnicas Biossensoriais , Mucoproteínas/análise , Proteínas Oncogênicas/análise , Anticorpos Monoclonais , Técnicas Eletroquímicas , Eletrodos , Ouro , Humanos , Limite de Detecção , Nanopartículas Metálicas , Neoplasias
15.
Biosensors (Basel) ; 11(6)2021 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-34200646

RESUMO

Coumaphos is an organophosphorus compound used as insecticide and frequently used by beekeepers for the management of parasitic mites. The most important metabolite, chlorferron (CFN), has been identified in biological samples and foodstuff. The need to quickly identify the presence of typical metabolites, as an indication of interaction with coumaphos has driven the need to produce a highly sensitive electrochemical method for chlorferron analysis, based on molecularly imprinting polymers (MIP) technology. It showed irreversible behaviour with mixed diffusion/adsorption-controlled reactions at the electrode surface. A monoelectronic mechanism of reaction for oxidation has also been suggested. The linear range observed was from 0.158 to 75 µM. Median precision in terms of %RSD around 3% was also observed. For DPV, the limit of detection (LOD) and the limit of quantitation (LOQ) for the CFN-MIP were 0.158 µM and 0.48 µM, respectively. The obtained median % recovery was around 98%. The results were also validated to reference values obtained using GC-MS. Urine and human synthetic plasma spiked with CFN were used to demonstrate the usability of the method in biological samples, showing the potential for biomonitoring. The developed imprinted sensor showed maximum signal change less than 16.8% when related metabolites or pesticide were added to the mix, suggesting high selectivity of the MIP sensor toward CFN molecules. The results from in vitro metabolism of CMP analysed also demonstrates the potential for detection and quantification of CFN in environmental samples. The newly developed CFN-MIP sensor offers similar LoDs than chromatographic methods with shorter analysis time.


Assuntos
Monitoramento Biológico/métodos , Polímeros Molecularmente Impressos , Umbeliferonas/análise , Adsorção , Técnicas Eletroquímicas , Eletrodos , Humanos , Limite de Detecção , Impressão Molecular , Polímeros , Umbeliferonas/química
16.
Biosensors (Basel) ; 11(6)2021 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-34200755

RESUMO

Prussian blue analogs (PBAs) are well-known artificial enzymes with peroxidase (PO)-like activity. PBAs have a high potential for applications in scientific investigations, industry, ecology and medicine. Being stable and both catalytically and electrochemically active, PBAs are promising in the construction of biosensors and biofuel cells. The "green" synthesis of PO-like PBAs using oxido-reductase flavocytochrome b2 is described in this study. When immobilized on graphite electrodes (GEs), the obtained green-synthesized PBAs or hexacyanoferrates (gHCFs) of transition and noble metals produced amperometric signals in response to H2O2. HCFs of copper, iron, palladium and other metals were synthesized and characterized by structure, size, catalytic properties and electro-mediator activities. The gCuHCF, as the most effective PO mimetic with a flower-like micro/nano superstructure, was used as an H2O2-sensitive platform for the development of a glucose oxidase (GO)-based biosensor. The GO/gCuHCF/GE biosensor exhibited high sensitivity (710 A M-1m-2), a broad linear range and good selectivity when tested on real samples of fruit juices. We propose that the gCuHCF and other gHCFs synthesized via enzymes may be used as artificial POs in amperometric oxidase-based (bio)sensors.


Assuntos
Técnicas Biossensoriais , Ferrocianetos/química , Peroxidase/análise , Fontes de Energia Bioelétrica , Eletroquímica , Eletrodos , Enzimas Imobilizadas , Glucose , Glucose Oxidase , Grafite , Peróxido de Hidrogênio , Oxirredutases , Paládio , Peroxidases
17.
Sensors (Basel) ; 21(13)2021 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-34282758

RESUMO

Electrical stimulation can be used to modulate activity within the nervous system in one of two modes: (1) Activation, where activity is added to the neural signalling pathways, or (2) Block, where activity in the nerve is reduced or eliminated. In principle, electrical nerve conduction block has many attractive properties compared to pharmaceutical or surgical interventions. These include reversibility, localization, and tunability for nerve caliber and type. However, methods to effect electrical nerve block are relatively new. Some methods can have associated drawbacks, such as the need for large currents, the production of irreversible chemical byproducts, and onset responses. These can lead to irreversible nerve damage or undesirable neural responses. In the present study we describe a novel low frequency alternating current blocking waveform (LFACb) and measure its efficacy to reversibly block the bradycardic effect elicited by vagal stimulation in anaesthetised rat model. The waveform is a sinusoidal, zero mean(charge balanced), current waveform presented at 1 Hz to bipolar electrodes. Standard pulse stimulation was delivered through Pt-Black coated PtIr bipolar hook electrodes to evoke bradycardia. The conditioning LFAC waveform was presented either through a set of CorTec® bipolar cuff electrodes with Amplicoat® coated Pt contacts, or a second set of Pt Black coated PtIr hook electrodes. The conditioning electrodes were placed caudal to the pulse stimulation hook electrodes. Block of bradycardic effect was assessed by quantifying changes in heart rate during the stimulation stages of LFAC alone, LFAC-and-vagal, and vagal alone. The LFAC achieved 86.2±11.1% and 84.3±4.6% block using hook (N = 7) and cuff (N = 5) electrodes, respectively, at current levels less than 110 µAp (current to peak). The potential across the LFAC delivering electrodes were continuously monitored to verify that the blocking effect was immediately reversed upon discontinuing the LFAC. Thus, LFACb produced a high degree of nerve block at current levels comparable to pulse stimulation amplitudes to activate nerves, resulting in a measurable functional change of a biomarker in the mammalian nervous system.


Assuntos
Bloqueio Nervoso , Condução Nervosa , Animais , Vias Autônomas , Estimulação Elétrica , Eletrodos , Ratos
18.
Molecules ; 26(11)2021 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-34198893

RESUMO

In this work, a low-cost and rapid electrochemical resistive DNA biosensor based on the current relaxation method is described. A DNA probe, complementary to the specific human papillomavirus type 16 (HPV-16) sequence, was immobilized onto a screen-printed gold electrode. DNA hybridization was detected by applying a potential step of 30 mV to the system, composed of an external capacitor and the modified electrode DNA/gold, for 750 µs and then relaxed back to the OCP, at which point the voltage and current discharging curves are registered for 25 ms. From the discharging curves, the potential and current relaxation were evaluated, and by using Ohm's law, the charge transfer resistance through the DNA-modified electrode was calculated. The presence of a complementary sequence was detected by the change in resistance when the ssDNA is transformed in dsDNA due to the hybridization event. The target DNA concentration was detected in the range of 5 to 20 nM. The results showed a good fit to the regression equation ΔRtotal(Ω)=2.99 × [DNA]+81.55, and a detection limit of 2.39 nM was obtained. As the sensing approach uses a direct current, the electronic architecture of the biosensor is simple and allows for the separation of faradic and nonfaradaic contributions. The simple electrochemical resistive biosensor reported here is a good candidate for the point-of-care diagnosis of HPV at a low cost and in a short detection time.


Assuntos
Técnicas Biossensoriais/instrumentação , DNA Viral/análise , Papillomavirus Humano 16/isolamento & purificação , Infecções por Papillomavirus/diagnóstico , Técnicas Eletroquímicas/instrumentação , Eletrodos , Ouro/química , Papillomavirus Humano 16/genética , Humanos , Limite de Detecção , Testes Imediatos
19.
J Nanosci Nanotechnol ; 21(12): 5795-5811, 2021 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-34229776

RESUMO

Widespread usage of pesticides in agricultural practice caused their residues to appear in water and food products intended for human consumption. The potential toxicity of these resources has raised awareness about pesticide tracking in the environment. Development of reliable electrochemical sensors for the on-site determination of pesticide concentrations is envisioned as an alternative to conventional chromatographic methods which are robust, expensive and require skilled work force. Modification of the working electrode surface can result in enhanced electrochemical response towards selected pesticide making such electrode convenient sensor for facile and efficient determination of pesticides in low concentrations. New generation of nanomaterials is applied in electrode modification in order to improve its sensitivity and selectivity. The present review summarizes significant advances in voltammetric detection of pesticides for the period of the past five years. The major focus of this review is set to the types of carbon and oxide based materials, metal nanoparticles, composites and other materials employed to upgrade standard electrode configurations such as glassy carbon and carbon paste electrodes, boron doped diamond electrodes, screen printed and film electrodes, metal and amalgam, and other kinds of electrodes.


Assuntos
Praguicidas , Boro , Carbono , Diamante , Técnicas Eletroquímicas , Eletrodos , Humanos , Praguicidas/análise
20.
J Nanosci Nanotechnol ; 21(12): 5881-5889, 2021 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-34229782

RESUMO

Recently, flexible electronic device technology has evolved beyond curved devices with the development of flexible/stretchable devices that can be crumpled or stretched. Both elasticity and durability are essential for these devices, which should have high-conductivity for antennas and repeatability for sensors. In addition, electronic-skins, which can have a direct impact on the human-body, should be harmless to the human-body and should not be deformed by contact with sweat or organic matter. In this study, PDMS substrates were used to satisfy the above conditions. PDMS is used to fabricate human-friendly, flexible/stretchable substrates, and it has excellent repeat durability characteristics. To improve the adhesion of these PDMS films and electrodes, conductive paste was produced based on PDMS resins of the same properties. In addition, two types of Ag particles were selected as conductive fillers because the electrode characteristics of the antenna application requires excellent conductivity, and conductive paste were produced using flake Ag, which could affect conductivity, and Ag nanoparticles that affect stretchability and repeatability. The paste was applied using a high-efficiency printing technique. The printed electrodes were cured in a thermal oven. For higher conductivity, photonic-sintering was carried out during post-processing. As a result, 1.1117×106 (S/m) had excellent conductivity, performed well in repeated tensile-durability experiments of 30% to 100 times, and produced a bow-tie antenna for the above electrodes. As a result of tensing up to 35% through a Network-Analyzer, there was no performance change in the resonance-frequency or return-loss values, and excellent electrodes were developed that would achieve excellent performance even if they are applied in the sub-frequency area of 5G-antennas in the future.


Assuntos
Nanopartículas Metálicas , Dispositivos Eletrônicos Vestíveis , Eletrodos , Eletrônica , Humanos , Prata
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