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1.
Small ; 18(10): e2105880, 2022 03.
Artigo em Inglês | MEDLINE | ID: mdl-34989480

RESUMO

Glyconanoparticles (GNPs) made by self-assembly of carbohydrate-based polystyrene-block-ß-cyclodextrin copolymer are used as a building block for the design of nanostructured biomaterials of electrode. The firm immobilization of GNPs is carried out on electrochemically generated polymer, poly(pyrrole-adamantane), and copolymer, poly(pyrrole-adamantane)/poly(pyrrole-lactobionamide) via host-guest interactions between adamantane and ß-cyclodextrin. The ability of GNPs for the specific anchoring of biological macromolecules is investigated using glucose oxidase enzyme modified by adamantane groups as a protein model (GOx-Ad). The immobilization of GOx-Ad is carried out by incubation of an aqueous enzyme solution on a coating of GNPs adsorbed on a platinum electrode. The presence of immobilized GOx-Ad is evaluated in aqueous glucose solution by potentiostating the underlying platinum electrode at 0.7 V/SCE for the electro-oxidation of H2 O2 generated by the enzyme. The analytical performance of the bioelectrodes for the detection of glucose is compared to control electrodes prepared without GNPs or without electropolymerized films. The better permeability of copolymer compared to polymer and the possibility to elaborate two alternating layers of GNPs and GOx-Ad are clearly observed. The best amperometric response is recorded with a multilayered bioelectrode displaying a wide linear range linear range of the calibration curve: 68 µmol L-1 to 0.1 mol L-1 .


Assuntos
Técnicas Biossensoriais , Nanopartículas , beta-Ciclodextrinas , Eletrodos , Enzimas Imobilizadas/química , Glucose/química , Glucose Oxidase/química , Nanopartículas/química , Pirróis/química , beta-Ciclodextrinas/química
2.
Comput Intell Neurosci ; 2022: 7607592, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35528348

RESUMO

The early diagnosis of stress symptoms is essential for preventing various mental disorder such as depression. Electroencephalography (EEG) signals are frequently employed in stress detection research and are both inexpensive and noninvasive modality. This paper proposes a stress classification system by utilizing an EEG signal. EEG signals from thirty-five volunteers were analysed which were acquired using four EEG sensors using a commercially available 4-electrode Muse EEG headband. Four movie clips were chosen as stress elicitation material. Two clips were selected to induce stress as it contains emotionally inductive scenes. The other two clips were chosen that do not induce stress as it has many comedy scenes. The recorded signals were then used to build the stress classification model. We compared the Multilayer Perceptron (MLP) and Long Short-Term Memory (LSTM) for classifying stress and nonstress group. The maximum classification accuracy of 93.17% was achieved using two-layer LSTM architecture.


Assuntos
Eletroencefalografia , Redes Neurais de Computação , Encéfalo , Eletrodos , Humanos , Filmes Cinematográficos
3.
Mikrochim Acta ; 189(5): 208, 2022 05 02.
Artigo em Inglês | MEDLINE | ID: mdl-35501498

RESUMO

S, N co-doped graphene quantum dot (S, N-GQD) materials have been composited via a one-pot pattern and used as photosensitive materials to construct a label-free photoelectrochemical (PEC) sensor. The PEC experiments show an enhanced photocurrent response toward Bisphenol A (BPA) sensing due to the increased charge transfer rate and the enhanced absorption of visible light. Compared with dark conditions, the photocurrent signal (- 0.2 V vs. SCE) is greatly increased because of the effective oxidation of BPA by photogenerated holes and the rapid electron transfer of S, N-GQDs on the PEC sensing platform. Under optimal conditions linear current response to BPA is in two ranges of 0.12-5 µM and 5-40 µM. The limit of detection is 0.04 µM (S/N = 3). The designed sensor has enduring stability and admirable interference immunity. It  provides an alternative approach for BPA determination in real samples with recoveries of 99.3-103% and  RSD of 2.0-4.1%.


Assuntos
Grafite , Pontos Quânticos , Compostos Benzidrílicos , Técnicas Eletroquímicas , Eletrodos , Fenóis
4.
Med Biol Eng Comput ; 60(6): 1801-1814, 2022 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-35505176

RESUMO

Power-line-interference (PLI) is one of the major disturbing factors in almost all ground-free biopotential acquisition applications. The body is a volume conductor and collects PLI currents. Some of these currents pass through the sensing electrodes, then the electrode cables, and finally via the amplifier input impedances they reach the signal ground. The electrode impedances and the amplifier input impedances form an impedance bridge. Due to electrode impedance instability over time, the bridge tends to be imbalanced and produces differential PLI which is amplified together with the useful signal. This paper describes a powerful mixed analog-digital solution for automatic impedance bridge balance using software PLL for line synchronization. The approach is implemented and validated through recorded real ECG signals. The PLI is canceled by adding part of the common-mode voltage, with automatically adjusted amplitude and phase, to the useful differential biosignal. The described approach produces high-quality biosignals without the need for a common-mode reference electrode. It is applicable to all biosignals taken with surface electrodes like ECG, EEG, EMG, EOG, etc., and can benefit all diagnostic and therapeutic medical devices where these signals are in use.


Assuntos
Amplificadores Eletrônicos , Eletrocardiografia , Impedância Elétrica , Eletrodos , Desenho de Equipamento
5.
Sci Rep ; 12(1): 7417, 2022 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-35523838

RESUMO

The presented paper fundamentally investigates the influence of different electron transfer mechanisms, various metal-based electrodes, and a static magnetic field on the overall performance of microfluidic microbial fuel cells (MFCs) for the first time to improve the generated bioelectricity. To do so, as the anode of microfluidic MFCs, zinc, aluminum, tin, copper, and nickel were thoroughly investigated. Two types of bacteria, Escherichia coli and Shewanella oneidensis MR-1, were used as biocatalysts to compare the different electron transfer mechanisms. Interaction between the anode and microorganisms was assessed. Finally, the potential of applying a static magnetic field to maximize the generated power was evaluated. For zinc anode, the maximum open circuit potential, current density, and power density of 1.39 V, 138,181 mA m-2 and 35,294 mW m-2 were obtained, respectively. The produced current density is at least 445% better than the values obtained in previously published studies so far. The microfluidic MFCs were successfully used to power ultraviolet light-emitting diodes (UV-LEDs) for medical and clinical applications to elucidate their application as micro-sized power generators for implantable medical devices.


Assuntos
Fontes de Energia Bioelétrica , Fontes de Energia Bioelétrica/microbiologia , Eletricidade , Eletrodos , Elétrons , Campos Magnéticos , Microfluídica , Zinco
6.
Anal Chim Acta ; 1208: 339851, 2022 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-35525595

RESUMO

We have designed and prepared an electrochemical biosensor for lactate determination. Through a diazotation process, the enzyme lactate oxidase (LOx) is anchored onto chevron-like graphene nanoribbons (GNR), previously synthesized by a solution-based chemical route, and used as modifiers of glassy carbon electrodes. In a first step, we have performed the grafting of a 4-carboxyphenyl film, by electrochemical reduction of the corresponding 4-carboxyphenyl diazonium salt, on the GNR-modified electrode surface. In this way, the carboxylic groups are exposed to the solution, enabling the covalent immobilization of the enzyme through the formation of an amide bond between these carboxylic groups and the amine groups of the enzyme. The biosensor design was optimized through the morphological and electrochemical characterization of each construction step by atomic force microscopy, scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy.The cyclic voltammetric response of the biosensor in a solution of hydroxymethylferrocene in presence of l-lactate evidenced a clear electrocatalytic effect powered by the specific design of the biosensing platform with LOx covalently attached to the GNR layer. From the calibration procedures employed for l-lactate determination, a linear concentration range of 3.4 · 10-5- 2.8 · 10-4 M and a detection limit of 11 µM were obtained, with relative errors and relative standard deviations less than 6.0% and 8.4%, respectively. The applicability of the biosensor was tested by determining lactate in apple juices, leading to results that are in good agreement with those obtained with a well-established enzymatic spectrophotometric assay kit.


Assuntos
Técnicas Biossensoriais , Grafite , Nanotubos de Carbono , Técnicas Biossensoriais/métodos , Técnicas Eletroquímicas/métodos , Eletrodos , Enzimas Imobilizadas/química , Grafite/química , Ácido Láctico , Oxigenases de Função Mista , Nanotubos de Carbono/química
7.
Sci Rep ; 12(1): 7507, 2022 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-35525846

RESUMO

In this work, we report a wafer-scale and chemical-free fabrication of nickel (Ni) and copper (Cu) heteroatomic Cu-Ni thin films using RF magnetron sputtering technique for non-enzymatic glucose sensing application. The as-prepared wafer-scale Cu-Ni thin films exhibits excellent electrocatalytic activity toward glucose oxidation with a 1.86 µM detection limit in the range of 0.01 mM to 20 mM range. The Cu-Ni film shows 1.3- and 5.4-times higher glucose oxidation activity in comparison to the Cu and Ni electrodes, respectively. The improved electrocatalytic activity is attributed to the synergistic effect of the bimetallic catalyst and high density of grain boundaries. The Cu-Ni electrodes also possessed excellent anti-interference characteristics. These results indicate that Cu-Ni heteroatomic thin film can be a potential candidate for the development of non-enzymatic glucose biosensor because of its chemical free synthesis, excellent reproducibility, reusability, and long-term stability.


Assuntos
Técnicas Biossensoriais , Níquel , Técnicas Biossensoriais/métodos , Cobre , Eletrodos , Glucose , Reprodutibilidade dos Testes
8.
Sci Rep ; 12(1): 7335, 2022 05 05.
Artigo em Inglês | MEDLINE | ID: mdl-35513410

RESUMO

Our long-term goal is the development of a wearable warning system that uses electrocutaneous stimulation. To find appropriate stimulation parameters and electrode configurations, we investigate perception amplitude thresholds and qualitative perceptions of electrocutaneous stimulation for varying pulse widths, electrode sizes, and electrode positions. The upper right arm was stimulated in 81 healthy volunteers with biphasic rectangular current pulses varying between 20 and [Formula: see text]. We determined perception, attention, and intolerance thresholds and the corresponding qualitative perceptions for 8 electrode pairs distributed around the upper arm. For a pulse width of [Formula: see text], we find median values of 3.5, 6.9, and 13.8 mA for perception, attention, and intolerance thresholds, respectively. All thresholds decrease with increasing pulse width. Lateral electrode positions have higher intolerance thresholds than medial electrode positions, but perception and attention threshold are not significantly different across electrode positions. Electrode size between [Formula: see text] and [Formula: see text] has no significant influence on the thresholds. Knocking is the prevailing perception for perception and attention thresholds while mostly muscle twitching, pinching, and stinging are reported at the intolerance threshold. Biphasic stimulation pulse widths between [Formula: see text] and [Formula: see text] are suitable for electric warning wearables. Within the given practical limits at the upper arm, electrode size, inter-electrode distance, and electrode position are flexible parameters of electric warning wearables. Our investigations provide the basis for electric warning wearables.


Assuntos
Percepção , Sensação , Estimulação Elétrica , Eletrodos , Humanos
9.
Comput Intell Neurosci ; 2022: 6414664, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35528339

RESUMO

The multichannel electrode array used for electromyogram (EMG) pattern recognition provides good performance, but it has a high cost, is computationally expensive, and is inconvenient to wear. Therefore, researchers try to use as few channels as possible while maintaining improved pattern recognition performance. However, minimizing the number of channels affects the performance due to the least separable margin among the movements possessing weak signal strengths. To meet these challenges, two time-domain features based on nonlinear scaling, the log of the mean absolute value (LMAV) and the nonlinear scaled value (NSV), are proposed. In this study, we validate the proposed features on two datasets, the existing four feature extraction methods, variable window size, and various signal-to-noise ratios (SNR). In addition, we also propose a feature extraction method where the LMAV and NSV are grouped with the existing 11 time-domain features. The proposed feature extraction method enhances accuracy, sensitivity, specificity, precision, and F1 score by 1.00%, 5.01%, 0.55%, 4.71%, and 5.06% for dataset 1, and 1.18%, 5.90%, 0.66%, 5.63%, and 6.04% for dataset 2, respectively. Therefore, the experimental results strongly suggest the proposed feature extraction method, for taking a step forward with regard to improved myoelectric pattern recognition performance.


Assuntos
Algoritmos , Reconhecimento Automatizado de Padrão , Eletrodos , Eletromiografia/métodos , Movimento , Reconhecimento Automatizado de Padrão/métodos
10.
Nano Lett ; 22(9): 3793-3800, 2022 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-35499312

RESUMO

Probe reactivity has long been considered to play a key role in artificial nanochannel sensors, but systematic studies of membrane wettability on detection performance are currently lacking. Inspired by biological aquaporins, we developed an effective strategy to regulate the hydrophilic/hydrophobic balance by the controllable in situ assembly of coordination polymers (CPs) using BDC-NH2 on anodic aluminum oxide (AAO) nanochannels to promote HCHO detection. We found that the hydrophobic/hydrophilic balance in CP/AAO heterosomes plays significant roles in the effective detection of HCHO. The hydrophobic AAO barrier layer is necessary to support the confinement effect, while the hydrophilic CP surface is favorable for HCHO to access the channels and then condense with the responsive amine to generate a new imine. The optimized CP/AAO Janus device shows excellent performance in the quantitative analysis of HCHO over a wide range from 100 pM to 1 mM by monitoring the rectified ionic current.


Assuntos
Aquaporinas , Técnicas Biossensoriais , Óxido de Alumínio/química , Eletrodos , Polímeros
11.
Mikrochim Acta ; 189(5): 185, 2022 04 09.
Artigo em Inglês | MEDLINE | ID: mdl-35396635

RESUMO

Graphene-based materials present unique properties for electrochemical applications, and laser-induced conversion of polyimide to graphene is an emerging route to obtain a high-quality material for sensing. Herein we present compact and low-cost equipment constructed from an open-source 3D printer at which a 3.5-W visible (449 nm) laser was adapted to fabricate laser-induced graphene (LIG) electrodes from commercial polyimide, which resulted in electron transfer kinetic (k0) of 5.6 × 10-3 cm s-1 and reproducibility calculated by relative standard deviation (RSD < 5%) from cyclic voltammograms of [Fe(CN)6]3-/4- using 5 different electrodes. LIG electrodes enabled the simultaneous voltammetric determination of uric acid (+ 0.1 V vs. pseudo-reference) and nitrite (+ 0.4 V vs pseudo-reference), with limit of detection (LOD) values of 0.07 and 0.27 µmol L-1, respectively. Amperometric measurements for the detection of H2O2 (applying + 0.0 V vs. Ag|AgCl|KCl(sat.)) after Prussian blue (PB) modification and ciprofloxacin (applying + 1.2 V vs. Ag|AgCl|KCl(sat.)) were performed under flow conditions, which confirmed the high stability of LIG and LIG-PB surfaces. The LOD values were 1.0 and 0.2 µmol L-1 for H2O2 and ciprofloxacin, respectively. The RSD values (< 12%) obtained for the analysis using three different electrodes attested the precision of LIG electrodes manufactured in two designs. No sample matrix effects on the determination of ciprofloxacin in milk samples were observed  (recoveries between 84 and 96%). The equipment can be built with less than $300 and each LIG electrode costs less than $0.01.


Assuntos
Grafite , Ciprofloxacina , Eletrodos , Grafite/química , Peróxido de Hidrogênio , Lasers , Reprodutibilidade dos Testes
12.
Mikrochim Acta ; 189(5): 188, 2022 04 11.
Artigo em Inglês | MEDLINE | ID: mdl-35404013

RESUMO

A laser-induced graphene (LIG) surface modified with Prussian blue (iron hexacyanoferrate) is demonstrated as a novel electrochemical sensing platform for the sensitive and selective detection of hydrogen peroxide. Electrochemical Prussian blue (PB) modification on porous graphene films engraved by infrared laser over flexible polyimide was accomplished. Scanning electron microscopy images combined with Raman spectra confirm the formation of porous graphene and homogenous electrodeposition of PB over this porous surface. Electrochemical impedance spectroscopy reveals a substantial decrease in the resistance to charge transfer values (from 395 to 31.4 Ω) after the PB insertion, which confirms the formation of a highly conductive PB-graphene composite. The synergistic properties of PB and porous graphene were investigated for the constant monitoring of hydrogen peroxide at 0.0 V vs. Ag|AgCl|KCl(sat.), under high-flow injections (166 µL s-1) confirming the high stability of the modified surface and fast response within a wide linear range (from 1 to 200 µmol L-1). Satisfactory detection limit (0.26 µmol L-1) and selectivity verified by the analysis of complex samples confirmed the excellent sensing performance of this platform. We highlight that the outstanding sensing characteristics of the developed sensor were superior in comparison with other PB-based or LIG-based electrochemical sensors reported for hydrogen peroxide detection.


Assuntos
Grafite , Técnicas Eletroquímicas/métodos , Eletrodos , Ferrocianetos , Grafite/química , Peróxido de Hidrogênio/análise , Lasers
13.
Anal Chim Acta ; 1206: 339777, 2022 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-35473858

RESUMO

We investigate electropolymerized molecularly imprinted polymers (E-MIPs) for the selective recognition of SARS-CoV-2 whole virus. E-MIPs imprinted with SARS-CoV-2 pseudoparticles (pps) were electrochemically deposited onto screen printed electrodes by reductive electropolymerization, using the water-soluble N-hydroxmethylacrylamide (NHMA) as functional monomer and crosslinked with N,N'-methylenebisacrylamide (MBAm). E-MIPs for SARS-CoV-2 showed selectivity for template SARS-CoV-2 pps, with an imprinting factor of 3:1, and specificity (significance = 0.06) when cross-reacted with other respiratory viruses. E-MIPs detected the presence of SARS-CoV-2 pps in <10 min with a limit of detection of 4.9 log10 pfu/mL, suggesting their suitability for detection of SARS-CoV-2 with minimal sample preparation. Using electrochemical impedance spectroscopy (EIS) and principal component analysis (PCA), the capture of SARS-CoV-2 from real patient saliva samples was also evaluated. Fifteen confirmed COVID-19 positive and nine COVID-19 negative saliva samples were compared against the established loop-mediated isothermal nucleic acid amplification (LAMP) technique used by the UK National Health Service. EIS data demonstrated a PCA discrimination between positive and negative LAMP samples. A threshold real impedance signal (ZRe) ≫ 4000 Ω and a corresponding charge transfer resistance (RCT) ≫ 6000 Ω was indicative of absence of virus (COVID-19 negative) in agreement with values obtained for our control non-imprinted polymer control. A ZRe at or below a threshold value of 600 Ω with a corresponding RCT of <1200 Ω was indicative of a COVID-19 positive sample. The presence of virus was confirmed by treatment of E-MIPs with a SARS-CoV-2 specific monoclonal antibody.


Assuntos
COVID-19 , Polímeros Molecularmente Impressos , Anticorpos Antivirais , COVID-19/diagnóstico , Eletrodos , Humanos , SARS-CoV-2 , Saliva , Medicina Estatal
14.
Nat Commun ; 13(1): 2253, 2022 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-35474069

RESUMO

Drug-induced cardiotoxicity arises primarily when a compound alters the electrophysiological properties of cardiomyocytes. Features of intracellular action potentials (iAPs) are powerful biomarkers that predict proarrhythmic risks. In the last decade, a number of vertical nanoelectrodes have been demonstrated to achieve parallel and minimally-invasive iAP recordings. However, the large variability in success rate and signal strength have hindered nanoelectrodes from being broadly adopted for proarrhythmia drug assessment. In this work, we develop vertically-aligned nanocrown electrodes that are mechanically robust and achieve > 99% success rates in obtaining intracellular access through electroporation. We validate the accuracy of nanocrown electrode recordings by simultaneous patch clamp recording from the same cell. Finally, we demonstrate that nanocrown electrodes enable prolonged iAP recording for continual monitoring of the same cells upon the sequential addition of four incremental drug doses. Our technology development provides an advancement towards establishing an iAP screening assay for preclinical evaluation of drug-induced arrhythmogenicity.


Assuntos
Fenômenos Eletrofisiológicos , Miócitos Cardíacos , Potenciais de Ação/fisiologia , Eletrodos , Eletroporação , Miócitos Cardíacos/fisiologia
15.
Mikrochim Acta ; 189(5): 200, 2022 04 26.
Artigo em Inglês | MEDLINE | ID: mdl-35474402

RESUMO

Three-dimensional (3D) cobalt molybdate (CoMoO4) hierarchical nanoflake arrays on pencil graphite electrode (PGE) (CoMoO4/PGE) are actualized via one-pot hydrothermal technique. The morphological features comprehend that the CoMoO4 nanoflake arrays expose the 3D, open, porous, and interconnected network architectures on PGE. The formation and growth mechanisms of CoMoO4 nanostructures on PGE are supported with different structural and morphological characterizations. The constructed CoMoO4/PGE is operated as an electrocatalytic probe in enzyme-less electrochemical glucose sensor (ELEGS), confronting the impairments of cost- and time-obsessed conventional electrode polishing and catalyst amendment progressions and obliged the employment of a non-conducting binder. The wide-opened interior and exterior architectures of CoMoO4 nanoflake arrays escalate the glucose utilization efficacy, whilst the intertwined nanoflakes and graphitic carbon layers, respectively, of CoMoO4 and PGE articulate the continual electron mobility and catalytically active channels of CoMoO4/PGE. It jointly escalates the ELEGS concerts of CoMoO4/PGE including high sensitivity (1613 µA mM-1 cm-2), wide linear glucose range (0.0003-10 mM), and low detection limit (0.12 µM) at a working potential of 0.65 V (vs. Ag/AgCl) together with the good recovery in human serum. Thus, the fabricated CoMoO4/PGE extends exclusive virtues of modest electrode production, virtuous affinity, swift response, and excellent sensitivity and selectivity, exposing innovative prospects to reconnoitring the economically viable ELEGSs with binder-free, affordable cost, and expansible 3D electrocatalytic probes.


Assuntos
Grafite , Cobalto , Eletrodos , Glucose , Grafite/química , Humanos , Prostaglandinas E
16.
Molecules ; 27(8)2022 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-35458591

RESUMO

Element doping and nanoparticle decoration of graphene is an effective strategy to fabricate biosensor electrodes for specific biomedical signal detections. In this study, a novel nonenzymatic glucose sensor electrode was developed with copper oxide (CuO) and boron-doped graphene oxide (B-GO), which was firstly used to reveal rhubarb extraction's inhibitive activity toward α-amylase. The 1-pyreneboronic acid (PBA)-GO-CuO nanocomposite was prepared by a hydrothermal method, and its successful boron doping was confirmed by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), in which the boron doping rate is unprecedentedly up to 9.6%. The CuO load reaches ~12.5 wt.%. Further electrochemical results showed that in the enlarged cyclic voltammograms diagram, the electron-deficient boron doping sites made it easier for the electron transfer in graphene, promoting the valence transition from CuO to the electrode surface. Moreover, the sensor platform was ultrasensitive to glucose with a detection limit of 0.7 µM and high sensitivity of 906 µA mM-1 cm-2, ensuring the sensitive monitoring of enzyme activity. The inhibition rate of acarbose, a model inhibitor, is proportional to the logarithm of concentration in the range of 10-9-10-3 M with the correlation coefficient of R2 = 0.996, and an ultralow limit of detection of ~1 × 10-9 M by the developed method using the PBA-GO-CuO electrode. The inhibiting ability of Rhein-8-b-D-glucopyranoside, which is isolated from natural medicines, was also evaluated. The constructed sensor platform was proven to be sensitive and selective as well as cost-effective, facile, and reliable, making it promising as a candidate for α-amylase inhibitor screening.


Assuntos
Técnicas Biossensoriais , Grafite , Boro , Cobre/química , Técnicas Eletroquímicas , Eletrodos , Glucose/química , Grafite/química , alfa-Amilases
17.
Molecules ; 27(8)2022 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-35458653

RESUMO

This work focuses on a carbon-based imprinted polymer composite, employed as a molecular recognition and sensing interface in fabricating a disposable electrochemical sensor. The carbon-paste electrode was made of a molecularly imprinted polymer comprising a copolymer of methacrylic acid as the functional monomer and blended crosslinking monomers of N,N'-methylenebisacrylamide, and ethylene glycol dimethacrylate, with theophylline as the template. The analytical properties of the proposed theophylline sensor were investigated, and the findings revealed an increase in differential pulse voltammetric current compared to the non-imprinted electrode. Under optimized conditions, the sensor has shown high sensitivity, high selectivity, lower detection limit (2.5 µg/mL), and satisfactory long-term stability. Further, the sensor was tested in whole bovine blood and validated without any matrix effect and cross-reactivity. Additionally, chronoamperometry of the sensor chip supported a rapid determination of THO with a short response time of 3 s. This carbon-paste electrode is highly specific for theophylline and may be applied as a drug sensor for clinical use.


Assuntos
Grafite , Impressão Molecular , Animais , Carbono/química , Bovinos , Técnicas Eletroquímicas , Eletrodos , Grafite/química , Limite de Detecção , Polímeros/química , Teofilina
18.
Molecules ; 27(8)2022 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-35458692

RESUMO

In this work, we present an electrochemical study of the boron cage monomercaptoundecahydro-closo-dodecaborate [B12H11SH]2- in solution and in a self-assembled monolayer over a polycrystalline gold electrode. Cyclic voltammetry of the anion [B12H11SH]2- in solution showed a shift in the peak potentials related to the redox processes of gold hydroxides, which evidences the interaction between the boron cage and the gold surface. For an Au electrode modified with the anion [B12H11SH]2-, cyclic voltammetry response of the probe Fe(CN)63-/Fe(CN)64- showed a ΔEp value typical for a surface modification. Electrochemical impedance spectroscopy presented Rtc and Cdl values related to the formation of a self-assembled monolayer (SAM). A comparison of electrochemical responses of a modified electrode with thioglycolic acid (TGA) reveals that the boron cage [B12H11SH]2- diminishes the actives sites over the Au surface due to the steric effects. Differential capacitance measurements for bare gold electrode and those modified with [B12H11SH]2- and (TGA), indicate that bulky thiols enhance charge accumulation at the electrode-solution interface. In addition to electrochemical experiments, DFT calculations and surface plasmon resonance measurements (SPR) were carried out to obtain quantum chemical descriptors and to evaluate the molecular length and the dielectric constant of the Boron cage. From SPR experiments, the adsorption kinetics of [B12H11SH]2- were studied. The data fit for a Langmuir kinetic equation, typical for the formation of a monolayer.


Assuntos
Boro , Ouro , Compostos de Boro , Eletrodos , Ouro/química , Ressonância de Plasmônio de Superfície
19.
Molecules ; 27(8)2022 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-35458750

RESUMO

Cathode thickness plays a major role in establishing an active area for an oxygen reduction reaction in energy converter devices, such as solid oxide fuel cells. In this work, we prepared SrFe0.9Ti0.1O3-δ-Ce0.8Sm0.2O1.9 composite cathodes with different layers (1×, 3×, 5×, 7×, and 9× layer). The microstructural and electrochemical performance of each cell was then explored through scanning electron microscopy and electrochemical impedance spectroscopy (EIS). EIS analysis showed that the area-specific resistance (ASR) decreased from 0.65 Ωcm2 to 0.12 Ωcm2 with the increase in the number of layers from a 1× to a 7×. However, the ASR started to slightly increase at the 9× layer to 2.95 Ωcm2 due to a higher loss of electrode polarization resulting from insufficient gas diffusion and transport. Therefore, increasing the number of cathode layers could increase the performance of the cathode by enlarging the active area for the reaction up to the threshold point.


Assuntos
Óxidos , Titânio , Eletrodos , Óxidos/química
20.
Sensors (Basel) ; 22(8)2022 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-35458984

RESUMO

A stable reference electrode (RE) plays a crucial role in the performance of an ion-sensitive field-effect transistor (ISFET) for bio/chemical sensing applications. There is a strong demand for the miniaturization of the RE for integrated sensor systems such as lab-on-a-chip (LoC) or point-of-care (PoC) applications. Out of several approaches presented so far to integrate an on-chip electrode, there exist critical limitations such as the effect of analyte composition on the electrode potential and drifts during the measurements. In this paper, we present a micro-scale solid-state pseudo-reference electrode (pRE) based on poly(3,4-ethylene dioxythiophene): poly(styrene sulfonic acid) (PEDOT:PSS) coated with graphene oxide (GO) to deploy with an ion-sensitive field-effect transistor (ISFET)-based sensor platform. The PEDOT:PSS was electropolymerized from its monomer on a micro size gold (Au) electrode and, subsequently, a thin GO layer was deposited on top. The stability of the electrical potential and the cross-sensitivity to the ionic strength of the electrolyte were investigated. The presented pRE exhibits a highly stable open circuit potential (OCP) for up to 10 h with a minimal drift of ~0.65 mV/h and low cross-sensitivity to the ionic strength of the electrolyte. pH measurements were performed using silicon nanowire field-effect transistors (SiNW-FETs), using the developed pRE to ensure good gating performance of electrolyte-gated FETs. The impact of ionic strength was investigated by measuring the transfer characteristic of a SiNW-FET in two electrolytes with different ionic strengths (1 mM and 100 mM) but the same pH. The performance of the PEDOT:PSS/GO electrode is similar to a commercial electrochemical Ag/AgCl reference electrode.


Assuntos
Técnicas Biossensoriais , Compostos Bicíclicos Heterocíclicos com Pontes , Eletrodos , Eletrólitos , Grafite , Íons , Polímeros
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