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1.
Talanta ; 281: 126878, 2025 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-39276570

RESUMO

This contribution describes the development of a simple, fast, cost-effective, and sensitive impedimetric immunosensor for quantifying bovine tuberculosis (TB) in bovine serum samples. The construction of the immunosensor involved immobilizing the purified protein derivative (PPD) of M. bovis onto a screen-printed electrode that was modified with gold nanoparticles (AuNPs) and a polypyrrole (pPy) film synthesized electrochemically. The immunosensor exhibited a linear range from 0.5 µg mL-1 to 100 µg mL-1 and achieved a limit of detection (LD) of 100 ng mL-1 for the detection of anti-M. bovis antibody. The recovery percentages obtained in bovine serum samples were excellent, ranging between 98 % and 103 %. This device presents several advantages over alternative methods for determining TB in bovine serum samples. These include direct, in situ measurement without the need for pre-treatment, utilization of small volumes, thus avoiding harmful solvents and expensive reagents, and portability. In addition, the immunosensor exhibits both physical and chemical stability, retaining effectiveness even after 30 days of modification. This allows simultaneous incubations and facilitates large-scale detection. Hence, this immunosensor presents itself as a promising diagnostic tool for detecting anti-M. bovis antibodies in bovine serum. It serves as a viable alternative to tuberculin and ELISA tests.


Assuntos
Técnicas Biossensoriais , Técnicas Eletroquímicas , Ouro , Nanopartículas Metálicas , Tuberculose Bovina , Animais , Bovinos , Tuberculose Bovina/diagnóstico , Tuberculose Bovina/sangue , Tuberculose Bovina/imunologia , Ouro/química , Técnicas Eletroquímicas/métodos , Imunoensaio/métodos , Técnicas Biossensoriais/métodos , Nanopartículas Metálicas/química , Mycobacterium bovis/imunologia , Polímeros/química , Pirróis/química , Eletrodos , Limite de Detecção , Anticorpos Antibacterianos/sangue , Anticorpos Antibacterianos/imunologia
2.
Front Chem ; 12: 1372292, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38606079

RESUMO

The concentration effect of Tradescantia spathacea (T. spathacea) as corrosion inhibitor of API 5L X52 steel in 0.5 M of H2SO4 was studied here through electrochemical and gravimetric techniques. To achieve it, samples of the material were prepared to be submitted to each of the tests. Results from electrochemical impedance spectroscopy (EIS) showed that there was an optimum concentration of the inhibitor in which is reached the maximum inhibition efficiency, displaying the best inhibition characteristics for this system with a maximum inhibition of 89% by using 400 ppm. However, the efficiency decreased until 40% when the temperature was increased to 60°C. Potentiodynamic polarization curves (PDP) revealed that some of the present compounds of T. spathacea may affect anodic and cathodic process, so it can be classified as a mix-type corrosion inhibitor for API 5L X52 in sulfuric acid. Also, this compound followed an adsorption mechanism; this can be described through a Frumkin isotherm with an adsorption standard free energy difference (ΔG°) of -56.59 kJmol-1. Metal surface was studied through scanning electron microscope, results revealed that by adding inhibitor, the metal surface is protected; also, they evidenced low damages compared with the surface with no inhibitor. Finally, Tradescantia spathacea inhibited the corrosion process with 82% efficiency.

3.
Materials (Basel) ; 17(8)2024 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-38673181

RESUMO

Biodiesel is a mixture of saturated and unsaturated Fatty Acid Methyl Esters (FAMEs) whose composition affects the corrosion behavior of metal containers during storage. This study examines the effect of the C=C bond present in selected FAMEs (Methyl Stearate, Methyl Oleate, and Methyl Linoleate) in aluminum corrosion in the absence of oxygen. First, mass loss assays were carried out at 100, 200, and 280 °C for 1000 h using pure Methyl Stearate (MS), 5% Methyl Oleate in Methyl Stearate (MS-5% MO), and 5% Methyl Linoleate in Methyl Stearate (MS-5% ML). Next, chemical changes in FAMEs were studied using FTIR, TGA, and GC/MS. SEM/EDS analysis allowed us to inspect the aluminum surfaces and their chemical characterization. We estimated higher corrosion rates for MS assays than those of unsaturated methyl ester mixtures. In a separate set of experiments, we used electrochemical techniques (potentiodynamic polarization, linear polarization resistance, and electrochemical impedance spectroscopy) to investigate aluminum corrosion induced by thermal-degraded products from FAMEs at 100, 200, and 280 °C for 300 h able to dissolve in aqueous extracts. These electrochemical experiments revealed that the products in the aqueous extracts from the unsaturated methyl ester mixture form a passive layer on the Al surface thicker than pure MS at the corresponding degradation temperatures.

4.
Mikrochim Acta ; 191(1): 76, 2024 01 04.
Artigo em Inglês | MEDLINE | ID: mdl-38172448

RESUMO

A new conductive ink based on the addition of carbon black to a poly(vinyl alcohol) matrix is developed and investigated for electrochemical sensing and biosensing applications. The produced devices were characterized using morphological and electrochemical techniques and modified with Pd nanoparticles to enhance electrical conductivity and reaction kinetics. With the aid of chemometrics, the parameters for metal deposition were investigated and the sensor was applied to the determination of Parkinson's disease biomarkers, specifically epinephrine and α-synuclein. A linear behavior was obtained in the range 0.75 to 100 µmol L-1 of the neurotransmitter, and the device displayed a limit of detection (LOD) of 0.051 µmol L-1. The three-electrode system was then tested using samples of synthetic cerebrospinal fluid. Afterward, the device was modified with specific antibodies to quantify α-synuclein using electrochemical impedance spectroscopy. In phosphate buffer, a linear range was obtained for α-synuclein concentrations from 1.5 to 15 µg mL-1, with a calculated LOD of 0.13 µg mL-1. The proposed immunosensor was also applied to blood serum samples, and, in this case, the linear range was observed from 6.0 to 100.5 µg mL-1 of α-synuclein, with a LOD = 1.3 µg mL-1. Both linear curves attend the range for the real diagnosis, demonstrating its potential application to complex matrices.


Assuntos
Técnicas Biossensoriais , Nanopartículas , Doença de Parkinson , Humanos , Doença de Parkinson/diagnóstico , alfa-Sinucleína , Técnicas Biossensoriais/métodos , Imunoensaio
5.
Materials (Basel) ; 16(12)2023 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-37374663

RESUMO

In this paper, the influence of a nickel binder metal and molybdenum carbide as an additional alloying element on the microstructure and corrosion behavior of WC-based cemented carbides, processed by conventional powder metallurgy, was studied, and a comparison with conventional cemented carbide (WC-Co) was carried out. The sintered alloys were characterized, before and after corrosive tests, by analyses using optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. The corrosion resistance of the cemented carbides was investigated by open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy in a 3.5 wt.% NaCl solution. The WC-NiMo cemented carbides showed microstructures similar to those of WC-Co; however, pores and binder islands were observed in the microstructures. The corrosion tests showed promising results, the WC-NiMo cemented carbide showed superior corrosion resistance and higher passivation capacity than the WC-Co cemented carbide. The WC-NiMo alloy showed a higher EOC ≈-0.18 V vs. Ag|AgCl|KCl3mol/L than the WC-Co (EOC≈-0.45 V vs. Ag|AgCl|KCl3mol/L). The potentiodynamic polarization curves showed lower current density values throughout the potential range for the WC-NiMo alloy, and it was observed that Ecorr was less negative (≈-0.416 V vs. Ag|AgCl|KCl3mol/L) than for WC-Co (≈-0.543 V vs. V vs. Ag|AgCl|KCl3mol/L). The EIS analysis confirmed low rate corrosion of WC-NiMo associated with the formation of a passive thin layer. This alloy showed a higher Rct (1970.70 Ω).

6.
Micromachines (Basel) ; 14(6)2023 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-37374847

RESUMO

Alzheimer's disease (AD) is a neurodegenerative disease with only late-stage detection; thus, diagnosis is made when it is no longer possible to treat the disease, only its symptoms. Consequently, this often leads to caregivers who are the patient's relatives, which adversely impacts the workforce along with severely diminishing the quality of life for all involved. It is, therefore, highly desirable to develop a fast, effective and reliable sensor to enable early-stage detection in an attempt to reverse disease progression. This research validates the detection of amyloid-beta 42 (Aß42) using a Silicon Carbide (SiC) electrode, a fact that is unprecedented in the literature. Aß42 is considered a reliable biomarker for AD detection, as reported in previous studies. To validate the detection with a SiC-based electrochemical sensor, a gold (Au) electrode-based electrochemical sensor was used as a control. The same cleaning, functionalization and Aß1-28 antibody immobilization steps were used on both electrodes. Sensor validation was carried out by means of Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) aiming to detect an 0.5 µg·mL-1 Aß42 concentration in 0.1 M buffer solution as a proof of concept. A repeatable peak directly related to the presence of Aß42 was observed, indicating that a fast SiC-based electrochemical sensor was constructed and may prove to be a useful approach for the early detection of AD.

7.
Biotechnol Prog ; 39(3): e3334, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36795023

RESUMO

This article developed a novel electrochemical immunosensor for the specific detection of aflatoxin B1 (AFB1). Amino-functionalized iron oxide nanoparticles (Fe3 O4 -NH2 ) were synthesized. Fe3 O4 -NH2 were chemically bound on self-assembly monolayers (SAMs) of mercaptobenzoic acid (MBA). Finally, polyclonal antibodies (pAb) were immobilized on Fe3 O4 -NH2 -MBA. The sensor system was evaluated through atomic force microscopy (AFM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). A reduction in the anodic and cathodic peak currents was observed after the assembly of the sensor platform. The charge transfer resistance (Rct ) was increased due to the electrically insulating bioconjugates. Then, the specific interaction between the sensor platform and AFB1 blocks the electron transfer of the [Fe(CN)6 ]3-/4- redox pair. The nanoimmunosensor showed a linear response range estimated from 0.5 to 30 µg/mL with a limit of detection (LOD) of 9.47 µg/mL and a limit of quantification (LOQ) of 28.72 µg/mL for AFB1 identification in a purified sample. In addition, a LOD of 3.79 µg/mL, a LOQ of 11.48 µg/mL, and a regression coefficient of 0.9891 were estimated for biodetection tests on peanut samples. The proposed immunosensor represents a simple alternative, successfully applied in detecting AFB1 in peanuts, and therefore, represents a valuable tool for ensuring food safety.


Assuntos
Arachis , Técnicas Biossensoriais , Aflatoxina B1/análise , Aflatoxina B1/química , Técnicas Biossensoriais/métodos , Técnicas Eletroquímicas/métodos , Imunoensaio , Limite de Detecção , Ouro/química
8.
Membranes (Basel) ; 12(11)2022 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-36422146

RESUMO

The surface modification of materials obtained from natural polymers, such as silk fibroin with metal nanoparticles that exhibit intrinsic electrical characteristics, allows the obtaining of biocomposite materials capable of favoring the propagation and conduction of electrical impulses, acting as communicating structures in electrically isolated areas. On that basis, this investigation determined the electrochemical and electroconductive behavior through electrochemical impedance spectroscopy of a silk fibroin electrospun membrane from silk fibrous waste functionalized with gold or silver nanoparticles synthetized by green chemical reduction methodologies. Based on the results obtained, we found that silk fibroin from silk fibrous waste (SFw) favored the formation of gold (AuNPs-SFw) and silver (AgNPs-SFw) nanoparticles, acting as a reducing agent and surfactant, forming a micellar structure around the individual nanoparticle. Moreover, different electrospinning conditions influenced the morphological properties of the fibers, in the presence or absence of beads and the amount of sample collected. Furthermore, treated SFw electrospun membranes, functionalized with AuNPs-SFw or AgNPS-SFw, allowed the conduction of electrical stimuli, acting as stimulators and modulators of electric current.

9.
Molecules ; 27(18)2022 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-36144512

RESUMO

Polypyrrole (PPy) is an interesting conducting polymer due to its good environmental stability, high conductivity, and biocompatibility. The association between PPy and metallic nanoparticles has been widely studied since it enhances electrochemical properties. In this context, gold ions are reduced to gold nanoparticles (AuNPs) directly on the polymer surface as PPy can be oxidized to an overoxidized state. This work proposes the PPy electrochemical synthesis followed by the direct reduction of gold on its surface in a fast reaction. The modified electrodes were characterized by electronic microscopic and infrared spectroscopy. The effect of reduction time on the electrochemical properties was evaluated by the electrocatalytic properties of the obtained material from the oxidation of ascorbic acid (AA) and electrochemical impedance spectroscopy studies. The presence of AuNPs improved the AA electrocatalysis by reducing oxidation potential and lowering charge transfer resistance. EIS data were fitted using a transmission line model. The results indicated an increase in the electronic transport of the polymeric film in the presence of AuNPs. However, PPy overoxidation occurs when the AuNPs' deposition is higher than 30 s. In PPy/AuNPs 15 s, smaller and less agglomerated particles were formed with fewer PPy overoxidized, confirming the observed electrocatalytic behavior.


Assuntos
Técnicas Biossensoriais , Nanopartículas Metálicas , Ácido Ascórbico , Técnicas Biossensoriais/métodos , Ouro/química , Íons , Polímeros/química , Pirróis/química
10.
ACS Nano ; 16(9): 14239-14253, 2022 09 27.
Artigo em Inglês | MEDLINE | ID: mdl-35969505

RESUMO

Limitations of the recognition elements in terms of synthesis, cost, availability, and stability have impaired the translation of biosensors into practical use. Inspired by nature to mimic the molecular recognition of the anti-SARS-CoV-2 S protein antibody (AbS) by the S protein binding site, we synthesized the peptide sequence of Asn-Asn-Ala-Thr-Asn-COOH (abbreviated as PEP2003) to create COVID-19 screening label-free (LF) biosensors based on a carbon electrode, gold nanoparticles (AuNPs), and electrochemical impedance spectroscopy. The PEP2003 is easily obtained by chemical synthesis, and it can be adsorbed on electrodes while maintaining its ability for AbS recognition, further leading to a sensitivity 3.4-fold higher than the full-length S protein, which is in agreement with the increase in the target-to-receptor size ratio. Peptide-loaded LF devices based on noncovalent immobilization were developed by affording fast and simple analyses, along with a modular functionalization. From studies by molecular docking, the peptide-AbS binding was found to be driven by hydrogen bonds and hydrophobic interactions. Moreover, the peptide is not amenable to denaturation, thus addressing the trade-off between scalability, cost, and robustness. The biosensor preserves 95.1% of the initial signal for 20 days when stored dry at 4 °C. With the aid of two simple equations fitted by machine learning (ML), the method was able to make the COVID-19 screening of 39 biological samples into healthy and infected groups with 100.0% accuracy. By taking advantage of peptide-related merits combined with advances in surface chemistry and ML-aided accuracy, this platform is promising to bring COVID-19 biosensors into mainstream use toward straightforward, fast, and accurate analyses at the point of care, with social and economic impacts being achieved.


Assuntos
Técnicas Biossensoriais , COVID-19 , Nanopartículas Metálicas , Técnicas Biossensoriais/métodos , COVID-19/diagnóstico , Teste para COVID-19 , Carbono/química , Técnicas Eletroquímicas , Eletrodos , Ouro/química , Humanos , Nanopartículas Metálicas/química , Simulação de Acoplamento Molecular , Peptídeos/química
11.
Heliyon ; 8(5): e09515, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35647356

RESUMO

With the aim of verifying the optical properties of the systems formed by poly(3-methylthiophene) (P3MT) and poly(3-octylthiophene) (P3OT) on platinum (Pt) for use in organic photovoltaic device applications, electrochemical preparations of different interfaces with poly(3-alkylthiophenes) (P3ATs), synthesized both with 18 °C and without temperature control, were compared. These interfaces were prepared both as blends (Pt/P3MT:P3OT) and as layered films (Pt/P3MT/P3OT and Pt/P3OT/P3MT). Electrochemical impedance spectroscopy (EIS) was used to characterize the systems, and based on Bode-Phase diagrams, it was possible to monitor the stabilization of radical cation and dication segments of the thiophene ring. The findings corroborated previous studies by electrochemical spectroscopy and using in situ Raman spectroscopy under the same experimental conditions. We were able to verify the effects of experimental variables, such as synthesis temperature and different kinds of deposition. Temperature was found to be an extremely important factor in synthesis, since films synthesized at 18 °C favored the stabilization of radical cation segments in the polymer matrix, and layered deposition also favored the stabilization of these segments, since the layer closest to the electrode can act as an induction layer for the stability of radical cation segments in the system. Photoluminescence spectroscopy was used to verify the optical properties of the interfaces, in which occur the contributions of three segments in the P3ATs matrix. Thus, it has been demonstrated through photoluminescence decay time that the relative amount of radical cation and dication segments in the polymer matrix affects the lifetime of these segments in the different materials prepared, due to emission effects for these systems.

12.
Molecules ; 27(9)2022 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-35566054

RESUMO

The detection of pathogens through alternative methodologies based on electrochemical biosensors is being studied. These devices exhibit remarkable properties, such as simplicity, specificity, and high sensitivity in monitoring pathogens. However, it is necessary to continue conducting studies that adequately improve these characteristics, especially the recognition molecule. This work aims to design and evaluate a new peptide, named PEPTIR-2.0, as a recognition molecule in electrochemical biosensors to detect E. coli O157:H7 in water. PEPTIR-2.0 was obtained from modifications of the PEPTIR-1.0 peptide sequence, which was previously reported and exhibited excellent properties for detecting and quantifying this pathogenic microorganism. PEPTIR-1.0 is a peptide analogous to the TIR (Translocated Intimin Receptor) protein capable of interacting with the Intimin outer membrane. The basis of this study was to obtain, by using bioinformatics tools, a molecule analogous to PEPTIR-1.0 that maintains its three-dimensional structure but increases the hydrophobic interactions between it and Intimin, since these intermolecular forces are the predominant ones. The designed PEPTIR-2.0 peptide was immobilized on screen-printed electrodes modified with gold nanoparticles. The detection capacity of E. coli O157:H7 in water was evaluated using electrochemical impedance spectroscopy in the presence of other microorganisms, such as P. aeruginosa, S. aureus, and non-pathogenic E. coli. The results showed that PEPTIR-2.0 confers remarkable specificity to the biosensor towards detecting E. coli, even higher than PEPTIR-1.0.


Assuntos
Técnicas Biossensoriais , Escherichia coli O157 , Nanopartículas Metálicas , Técnicas Biossensoriais/métodos , Escherichia coli O157/química , Ouro/química , Peptídeos/química , Staphylococcus aureus , Água
13.
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
14.
Food Chem ; 385: 132678, 2022 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-35290953

RESUMO

This study aimed to evaluate the applicability of electrochemical impedance spectroscopy to identify raw bovine milk adulteration with urea. Three batches of raw milk adulterated with urea were studied. Hierarchical clustering indicated that the samples could be split in three groups corresponding to low adulteration (less than 7 wt%), medium adulteration (between 8 and 16 wt%) and high adulteration (over than 16 wt%). A linear discriminant analysis was performed resulting in 90% of accuracy in classifying between groups. Besides, a partial least squares model containing three directions provided good accuracy in quantitatively predicting the urea mass fraction added to raw bovine milk. Finally, calculations using an approximated electric circuit model suggested the formation of urea aggregates that hinder charge transportation within the milk thus diminishing the solution conductivity. Results indicate that electrochemical impedance spectroscopy can be a useful, low cost and rapid tool to identify milk adulteration with urea.


Assuntos
Contaminação de Alimentos , Leite , Animais , Espectroscopia Dielétrica , Contaminação de Alimentos/análise , Análise dos Mínimos Quadrados , Leite/química , Ureia/análise
15.
Mikrochim Acta ; 189(3): 127, 2022 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-35233646

RESUMO

Smart electronic devices based on micro-controllers, also referred to as fashion electronics, have raised wearable technology. These devices may process physiological information to facilitate the wearer's immediate biofeedback in close contact with the body surface. Standard market wearable devices detect observable features as gestures or skin conductivity. In contrast, the technology based on electrochemical biosensors requires a biomarker in close contact with both a biorecognition element and an electrode surface, where electron transfer phenomena occur. The noninvasiveness is pivotal for wearable technology; thus, one of the most common target tissues for real-time monitoring is the skin. Noninvasive biosensors formats may not be available for all analytes, such as several proteins and hormones, especially when devices are installed cutaneously to measure in the sweat. Processes like cutaneous transcytosis, the paracellular cell-cell unions, or even reuptake highly regulate the solutes content of the sweat. This review discusses recent advances on wearable devices based on electrochemical biosensors for biomarkers with a complex blood-to-sweat partition like proteins and some hormones, considering the commented release regulation mechanisms to the sweat. It highlights the challenges of wearable epidermal biosensors (WEBs) design and the possible solutions. Finally, it charts the path of future developments in the WEBs arena in converging/emerging digital technologies.


Assuntos
Técnicas Biossensoriais , Dispositivos Eletrônicos Vestíveis , Biomarcadores/análise , Hormônios/análise , Suor/química
16.
Bioelectrochemistry ; 144: 108003, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-34906820

RESUMO

Although microbial fuel cells (MFCs) are an attractive alternative to environmental remediation and power generation, there are still significant limitations related to power density and coulombic efficiency. Previous works have shown that the addition of humic acids (HA, a type of organic matter contained in soils and composting-by-products), improves the fuel to electricity conversion at the porous bioanodes (ba)|anolyte junction. In this work, MFCs having HA-modified bioanodes (MFC/baHA) were prepared and electrochemically analyzed utilizing discharge curves (cell potential vs current density plots) and electrochemical impedance spectroscopy (EIS). This investigation was motivated by looking for a deeper understanding of the functional effects of HA molecules on the operation of baHA-containing Microbial Fuel Cells (MFC/baHA). Our results revealed that the modification of bioanodes with HA molecules decreases the activation energy of the acetate ion oxidation, increasing by a factor of three the consumption rate of this fuel at the baHA|anolyte interface, and enhancing the diffusive transport of these ions through the pores of the baHA permeated by the anolyte.


Assuntos
Fontes de Energia Bioelétrica
17.
Molecules ; 26(24)2021 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-34946501

RESUMO

Croton lechleri, commonly known as Dragon's blood, is a tree cultivated in the northwest Amazon rainforest of Ecuador and Peru. This tree produces a deep red latex which is composed of different natural products such as phenolic compounds, alkaloids, and others. The chemical structures of these natural products found in C. lechleri latex are promising corrosion inhibitors of admiralty brass (AB), due to the number of heteroatoms and π structures. In this work, three different extracts of C. lechleri latex were obtained, characterized phytochemically, and employed as novel green corrosion inhibitors of AB. The corrosion inhibition efficiency (IE%) was determined in an aqueous 0.5 M HCl solution by potentiodynamic polarization (Tafel plots) and electrochemical impedance spectroscopy, measuring current density and charge transfer resistance, respectively. In addition, surface characterization of AB was performed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy techniques. Chloroform alkaloid-rich extracts resulted in IE% of 57% at 50 ppm, attributed to the formation of a layer of organic compounds on the AB surface that hindered the dezincification process. The formulation of corrosion inhibitors from C. lechleri latex allows for the valorization of non-edible natural sources and the diversification of the offer of green corrosion inhibitors for the chemical treatment of heat exchangers.


Assuntos
Cobre/química , Croton/química , Ácido Clorídrico/química , Extratos Vegetais/química , Zinco/química , Corrosão
18.
Microbiol Res ; 251: 126834, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34364021

RESUMO

Biosensors are pre-prepared diagnostic devices composed of at least one biological probe. These devices are envisaged for the practical identification of specific targets of microbiological interest. In recent years, the use of narrow-specific probes such as lectins has been proven to distinguish bacteria and glycoproteins based on their superficial glycomic pattern. For instance, Concanavalin A is a carbohydrate-binding lectin indicated as a narrow-specific biological probe for Gram-negative bacteria. As a drawback, Gram-positive bacteria are frequently overlooked from lectin-based biosensing studies because their identification results in low resolution and overlapped signals. In this work, the authors explore the effect that platform nanostructuration has over the electrochemical response of ConA-based platforms constructed for bacterial detection; one is formed of chitosan-capped magnetic nanoparticles, and another is composed of gold nanoparticle-decorated magnetic nanoparticles. The biosensing platforms were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) as a function of bacterial concentration. Our results show that probe-target interaction causes variations in the electrical responses of nanostructured transducers. Moreover, the association of gold nanoparticles to magnetic nanoparticles resulted in an electrical enhancement capable of overcoming low resolution and overlapping Gram-positive identification. Both platforms attained a limit of detection of 10 ° CFU mL-1, which is useful for water analyses and sanitation concerns, where low CFU mL-1 are always expected. Although both platforms were able to detect Gram-negative bacteria, Gram-positives were only correctly differentiated by the gold nanoparticle-decorated magnetic nanoparticles, thus demonstrating the positive influence of hierarchically nanostructured platforms.


Assuntos
Técnicas Biossensoriais , Concanavalina A , Bactérias Gram-Positivas , Técnicas Biossensoriais/métodos , Concanavalina A/farmacologia , Ouro , Bactérias Gram-Positivas/classificação , Bactérias Gram-Positivas/efeitos dos fármacos , Nanopartículas Metálicas , Transdutores
19.
Anal Bioanal Chem ; 413(25): 6393-6399, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34389880

RESUMO

Saxitoxin is a cyanotoxin which is very harmful to human health; the concentration limit in drinking water is only 3 µg/L. Therefore, a simple, fast, sensitive, low-cost, and specific method for its detection, quantification, and monitoring in water bodies is needed to avoid adverse effects on animal and human health. In this work, we developed an electrochemical impedimetric biosensor using a specific aptamer as recognition element for saxitoxin detection. This method allies the superior sensing characteristics of aptamers with the nondestructive, label-free, and easy working principles of the electrochemical impedance technique. The device presented sensitivity for detecting saxitoxin concentrations above 0.3 µg/L, with high selectivity in negative control experiments, demonstrating a promising alternative for water toxin detection.

20.
Anal Bioanal Chem ; 413(18): 4673-4680, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34046698

RESUMO

A fast PCR-assisted impedimetric biosensor was developed for the selective detection of the clbN gene from the polyketide synthase (pks) genomic island in real Escherichia coli samples. This genomic island is responsible for the production of colibactin, a harmful genotoxin that has been associated with colorectal cancer. The experimental protocol consisted of immobilizing the designated forward primer onto an Au electrode surface to create the sensing probe, followed by PCR temperature cycling in blank, positive, and negative DNA controls. Target DNA identification was possible by monitoring changes in the system's charge transfer resistance values (Rct) before and after PCR treatment through electrochemical impedance spectroscopy (EIS) analysis. Custom-made, flexible gold electrodes were fabricated using chemical etching optical lithography. A PCR cycle study determined the optimum conditions to be at 6 cycles providing fast results while maintaining a good sensitivity. EIS data for the DNA recognition process demonstrated the successful distinction between target interaction resulting in an increase in resistance to charge transfer (Rct) percentage change of 176% for the positive DNA control vs. 21% and 20% for the negative and non-DNA-containing controls, respectively. Results showed effective fabrication of a fast, PCR-based electrochemical biosensor for the detection of pks genomic island with a calculated limit of detection of 17 ng/µL.


Assuntos
Técnicas Biossensoriais/métodos , Espectroscopia Dielétrica/métodos , Escherichia coli/genética , Genoma Bacteriano , Peptídeos/genética , Policetídeo Sintases/genética , Reação em Cadeia da Polimerase/métodos , Limite de Detecção , Policetídeos
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