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Electroanalytical chemistry has been advanced through portable devices, providing methods and sensors for the detection of analytes with high sensitivity and accuracy. This subfield of electrochemistry has the potential to be utilized in industry and analytical quality control, in general. This results in an increasing demand for trained personnel, capable of operating benchtop and portable electroanalytical equipment. Although electrochemical techniques are routinely taught in theoretical undergraduate courses, they need to be more often incorporated into experimental didactic activities. Herein, we describe the application of an effective, hands-on, and low-maintenance experiment that can enhance the learning experience of electroanalytical methods and their use in industrial quality control settings. This activity is based on the detection of ascorbic acid (vitamin C) by employing cyclic voltammetry at unmodified glassy carbon electrodes (GCE) in real juice samples. This didactic experiment teaches students about the theoretical concepts of cyclic voltammetry, three-electrode cell setup, chemical reversibility, data treatment, and quantitative analysis. This teaching approach was conducted in a second-year analytical chemistry course and was easily adapted to social distancing measures imposed by the COVID-19 pandemic.
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Electrochemical biosensors are known for their high sensitivity, selectivity, and low cost. Recently, they have gained significant attention and became particularly important as promising tools for the detection of COVID-19 biomarkers, since they offer a rapid and accurate means of diagnosis. Biorecognition strategies are a crucial component of electrochemical biosensors and determine their specificity and sensitivity based on the interaction of biological molecules, such as antibodies, enzymes, and DNA, with target analytes (e.g., viral particles, proteins and genetic material) to create a measurable signal. Different biorecognition strategies have been developed to enhance the performance of electrochemical biosensors, including direct, competitive, and sandwich binding, alongside nucleic acid hybridization mechanisms and gene editing systems. In this review article, we present the different strategies used in electrochemical biosensors to target SARS-CoV-2 and other COVID-19 biomarkers, as well as explore the advantages and disadvantages of each strategy and highlight recent progress in this field. Additionally, we discuss the challenges associated with developing electrochemical biosensors for clinical COVID-19 diagnosis and their widespread commercialization.
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Técnicas Biosensibles , COVID-19 , Humanos , COVID-19/diagnóstico , SARS-CoV-2/genética , Prueba de COVID-19 , Biomarcadores , Técnicas ElectroquímicasRESUMEN
Cytochrome c oxidase deficiency (COXD) is an inherited disorder characterized by the absence or mutation in the genes encoding for the cytochrome c oxidase protein (COX). COX deficiency results in severe muscle weakness, heart, liver, and kidney disorders, as well as brain damage in infants and adolescents, leading to death in many cases. With no cure for this disorder, finding an efficient, inexpensive, and early means of diagnosis is essential to minimize symptoms and long-term disabilities. Furthermore, muscle biopsy, the traditional detection method, is invasive, expensive, and time-consuming. This study demonstrates the applicability of scanning electrochemical microscopy to quantify COX activity in living human fibroblast cells. Taking advantage of the interaction between the redox mediator N, N, N', N'-tetramethyl-para-phenylene-diamine, and COX, the enzymatic activity was successfully quantified by monitoring current changes using a platinum microelectrode and determining the apparent heterogeneous rate constant k0 using numerical modeling. This study provides a foundation for developing a diagnostic method for detecting COXD in infants, which has the potential to increase treatment effectiveness and improve the quality of life of affected individuals.
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Deficiencia de Citocromo-c Oxidasa , Lactante , Humanos , Adolescente , Deficiencia de Citocromo-c Oxidasa/genética , Microscopía Electroquímica de Rastreo , Calidad de Vida , Complejo IV de Transporte de Electrones/metabolismo , Fibroblastos/metabolismoRESUMEN
Scanning electrochemical microscopy (SECM) is being used increasingly to monitor electrochemical processes at the interface of living cells and electrodes. This allows the detection and quantification of biomarkers that further the understanding of various diseases. Rapid SECM experiments are often carried out without monitoring the analyte solution temperature or are performed at room temperature. The reported research demonstrates that temperature control is crucial during SECM imaging of living cells to obtain reliable data. In this study, a SECM-integrated thermostatic ring on the sample stage enabled imaging of living biological cells in a constant height mode at various temperatures. Two-dimensional line scans were conducted while scanning single Adenocarcinoma Cervical cancer (HeLa) cells. Numerical modeling was carried out to evaluate the effect of the temperature on the electrochemical current response of living cells to compare the apparent heterogeneous rate constant (k0), representing cellular reaction kinetics. This study reveals that even slight temperature variations of approximately 2 °C affect the reaction kinetics of single living cells, altering the measured current during SECM.
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Diagnóstico por Imagen , Humanos , Microscopía Electroquímica de Rastreo , Temperatura , Electrodos , Células HeLaRESUMEN
Produced as toxic metabolites by fungi, mycotoxins, such as ochratoxin A (OTA), contaminate grain and animal feed and cause great economic losses. Herein, we report the fabrication of an electrochemical sensor consisting of an inexpensive and label-free carbon black-graphite paste electrode (CB-G-CPE), which was fully optimized to detect OTA in durum wheat matrices using differential pulse voltammetry (DPV). The effect of carbon paste composition, electrolyte pH and DPV parameters were studied to determine the optimum conditions for the electroanalytical determination of OTA. Full factorial and central composite experimental designs (FFD and CCD) were used to optimize DPV parameters, namely pulse width, pulse height, step height and step time. The developed electrochemical sensor successfully detected OTA with detection and quantification limits equal to 57.2 nM (0.023 µg mL-1) and 190.6 nM (0.077 µg mL-1), respectively. The accuracy and precision of the presented CB-G-CPE was used to successfully quantify OTA in real wheat matrices. This study presents an inexpensive and user-friendly method with potential applications in grain quality control.
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Grafito , Triticum , Animales , Técnicas Electroquímicas/métodos , Carbono/química , Grafito/química , ElectrodosRESUMEN
Microelectrodes as analytical sensing tools have gained immense popularity in a wide range of applications, ranging from probe design advancement to single live cell imaging. Micro-optical-ring electrodes (MOREs) are micro-scale ring-electrodes with an optical fiber core, that enables the MORE to conduct an optical signal while performing electrochemistry. Herein, we present a user-friendly and cost-effective method to fabricate MOREs for scanning photoelectrochemical microscopy (SPECM) applications. MOREs were characterized by electrochemistry, numerical modelling, and scanning electron microscopy (SEM), ensuring reproducibility in terms of a well-defined geometry and functionality. In this study, the integration of MOREs into scanning probe microscopy enabled the spectro-electrochemical detection of N, N, N, N'- Tetramethyl-p-phenyl-enediamine (TMPD) and its oxidized radical cation counterpart. UV-VIS spectroscopy capabilities of MOREs were optimized through tip-to-substrate distance variations. To demonstrate the applicability of MOREs to electrochemical single live cell imaging, oxygen production was detected in living algae (Eremosphaera viridis) by local illumination and concurrent electrochemical measurements.
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Técnicas Biosensibles , Microscopía , Técnicas Biosensibles/métodos , Electrodos , Microelectrodos , Microscopía Electrónica de Rastreo , Oxígeno , Reproducibilidad de los ResultadosRESUMEN
The emergence and spread of bacterial resistance to antibiotics has developed into one of the most challenging threats to public health. Antibiotic susceptibility tests (ASTs) for bacterial infections are now essential, because they provide guidance for physicians in the selection of antibiotics, to which bacteria will respond. Most current AST methods require long periods of time, because of bacterial growth and incubation, leading to a prolonged and overuse of broad-spectrum antibiotics. Thus, there is a growing demand for methods and technologies that enable rapid antibiotic susceptibility assessment. Due to advantages related to cost-effectiveness, rapid response time and high sensitivity, electrochemical detection methods are promising analytical tools that can successfully quantify antibiotic uptake and retention in clinically relevant bacterial strains. This study presents the electroanalytical quantification of tobramycin (TOB) retention in susceptible and resistant bacterial strains of Pseudomonas aeruginosa. The electrochemical behavior of TOB was characterized by voltammetry, identifying redox potentials, the current dependence on pH conditions, and the detection limit at unmodified glassy carbon electrodes. The presented methodology was able to distinguish between susceptible and resistant bacterial strains, and is also capable of identifying varying degrees of resistance against TOB. The presented approach detects the immediate interaction of bacteria with an antibiotic, without the need of complex and cost-intense equipment related to genomic testing methods.
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Infecciones por Pseudomonas , Tobramicina , Antibacterianos/farmacología , Carbono , Humanos , Pruebas de Sensibilidad Microbiana , Infecciones por Pseudomonas/tratamiento farmacológico , Infecciones por Pseudomonas/microbiología , Pseudomonas aeruginosa , Tobramicina/farmacologíaRESUMEN
Rapid determination of antibiotic residues is crucial for both environmental monitoring and the ecosystem. The presented study explores the development of a sensitive, selective, and highly reproducible chemical sensor to detect the antibiotic ciprofloxacin (Cip) in 0.1 M NaNO3 and in tap water. The designed sensor was constructed using oxygen functionalized carbon nanotubes (OCNTs), a layer of conductive polymer (polydopamine; PDA), and electro-deposited silver nanoparticles (Ag-NPs) at a glassy carbon electrode. Double-pulse electro-deposition was employed, as it offers numerous advantages including quick analysis time (s, ms), high reproducibility, and does not require expensive complexing agents, even at room temperature. The fabricated chemical sensor was fully optimized and characterized using physiochemical and electrochemical techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and voltammetry. Electrochemical measurements demonstrate high applicability of the chemical sensor towards the detection of Cip in the pico-molar concentration range. Detection and quantification levels were determined and the stability of the sensor was assessed. The obtained results demonstrate the potential of the OCNTs-PDA-Ag sensor to detect Cip in environmental samples.
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Nanopartículas del Metal , Nanotubos de Carbono , Antibacterianos , Ciprofloxacina , Ecosistema , Técnicas Electroquímicas/métodos , Electrodos , Límite de Detección , Nanopartículas del Metal/química , Nanotubos de Carbono/química , Reproducibilidad de los Resultados , Plata/químicaRESUMEN
Antibiotic resistance is a significant challenge encountered by healthcare systems on a global scale. Knowledge about membrane transport of antibiotics and other pharmacologically relevant molecules in bacteria is crucial towards understanding and overcoming antibiotic resistance, as drug resistance often depends on drug transport. This comprehensive literature review discusses the detection and quantification of membrane transport of pharma-molecules in bacteria and highlights the importance of molecule transport to antibiotic resistance. This review emphasizes electrochemical and electrophysiological methods of detection and quantification. The results of this literature review reveal a substantial diversity in methods and types of quantitative information collected.
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Antibacterianos/farmacología , Bacterias/efectos de los fármacos , Técnicas Electroquímicas , Antibacterianos/química , Farmacorresistencia Bacteriana/efectos de los fármacosRESUMEN
Bacterial infections present one of the leading causes of mortality worldwide, resulting in an urgent need for sensitive, selective, cost-efficient, and easy-to-handle technologies to rapidly detect contaminations and infections with pathogens. The presented research reports a fully functional chemical-detection principle, addressing all of the above-mentioned requirements for a successful biosensing device. With the examples of Escherichia coli and Neisseria gonorrheae, we present an electrochemical biosensor based on the bacterial expression of cytochrome c oxidase for the selective detection of clinically relevant concentrations within seconds after pathogen immobilization. The generality of the biochemical reaction, as well as the easy substitution of target-specific antibodies make this concept applicable to a large number of different pathogenic bacteria. The successful transfer of this semidirect detection principle onto inexpensive, screen-printed electrodes for portable devices represents a potential major advance in the field of biosensor development.
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Técnicas Biosensibles/métodos , Recuento de Células/métodos , Técnicas Electroquímicas/métodos , Escherichia coli/aislamiento & purificación , Neisseria gonorrhoeae/aislamiento & purificación , Anticuerpos Inmovilizados , Avidina/química , Células Inmovilizadas , Técnicas Electroquímicas/instrumentación , Electrodos , Complejo IV de Transporte de Electrones/química , Escherichia coli/enzimología , Escherichia coli/inmunología , Oro/química , Límite de Detección , Neisseria gonorrhoeae/enzimología , Neisseria gonorrhoeae/inmunología , Oxidación-Reducción , Tetrametilfenilendiamina/químicaRESUMEN
The electrochemical dissolution of citrate-capped gold nanoparticles (AuNPs) was studied in cyanide (CN-) containing solutions. It was found that the gold nanoparticles exhibited different dissolution behaviours as ensembles compared to the single particles. At the single particle level, a nearly complete oxidation of 60 nm AuNPs was achieved at concentrations greater than or equal to 35.0 mM CN- and at a potential of 1.0 V. Mechanistic insights and rate data are reported.
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We report the redox mediated detection of Escherichia coli bacteria at carbon microelectrodes, using the impact electrochemistry technique. By employing N,N,N',N'-tetramethyl-para-phenylene-diamine (TMPD) as redox mediator a concentration dependency for bacteria impacts was observed, whereby its impact frequency is shown to be in good agreement with theoretically predicted values.
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Técnicas Electroquímicas/métodos , Escherichia coli/aislamiento & purificación , Carbono/química , Complejo IV de Transporte de Electrones/química , Proteínas de Escherichia coli/química , Microelectrodos , Oxidación-Reducción , Tetrametilfenilendiamina/químicaRESUMEN
Bacterial infections represent one of the leading causes of mortality worldwide, nevertheless the design and development of rapid, cost-efficient and reliable detection methods for pathogens remains challenging. In recent years, electrochemical sensing methods have gained increasing attention for the detection of pathogenic bacteria, due to their increasingly competitive sensitivity. However, combining sensitivity with cost efficiency, high selectivity and a facile working procedure in a portable device is difficult. The presented review provides a summary of biosensing strategies for bacteria, published since 2015, by covering significant achievements towards custom-designed portable point-of-care devices. Herein, the direct chemical recognition of bacteria via enzyme activity or secretion products, as well as their detection at various electrode surfaces and materials, such as nanomaterials, indium tin oxide or paper-based immunosensors, is discussed. Furthermore, newly established hyphenated sensing principles, incorporated into lab-on-a-chip and microfluidic devices, are presented and remaining technical challenges and limitations are considered.
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Bacterias/aislamiento & purificación , Técnicas Biosensibles/métodos , Técnicas Electroquímicas/métodos , Anticuerpos/inmunología , Bacterias/inmunología , ADN/química , Electrodos , Dispositivos Laboratorio en un Chip , Límite de Detección , Nanoestructuras/químicaRESUMEN
We report the electrochemical sensing of Hg2+ based on tannic acid capped gold nanoparticle (AuNP@TA) complexes. At optimal conditions using square wave voltammetry, the presented analytical method exhibits a "measurable lower limit" of 100.0 fM. This limit is considerably below the permissible level of 30.0 nM for inorganic mercury in drinking water, specified by the World Health Organization (WHO). The effect of potentially interfering ions, such as Zn2+ and Al3+, was studied and results indicate an excellent selectivity for Hg2+. The transfer of the proposed strategy onto AuNP@TA modified screen-printed electrodes demonstrates its applicability to routine monitoring of Hg2+ in tap water.
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Controlled payload release is one of the key elements in the creation of a reliable drug delivery system. We report the discovery of a drug delivery vessel able to transport chemotherapeutic agents to target cancer cells and selectively trigger their release using the electrochemical activity of a ferrocene-modified phospholipid. Supported by in vitro assays, the competitive advantages of this discovery are (i) the simple one step scalability of the synthetic process, (ii) the stable encapsulation of toxic drugs (doxorubicin) during transport, and (iii) the selective redox triggering of the liposomes to harness their cytotoxic payload at the cancer site. Specifically, the redox-modified giant unilamellar vesicle and liposomes were characterized using advanced methods such as scanning electrochemical microscopy (SECM), transmission electron microscopy (TEM), dynamic light scattering (DLS), and fluorescent imaging.
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Portadores de Fármacos/química , Liberación de Fármacos , Compuestos Ferrosos/química , Metalocenos/química , Fosfolípidos/química , Doxorrubicina/química , Células HeLa , Humanos , Oxidación-ReducciónRESUMEN
Scanning electrochemical microscopy (SECM) allows imaging and analysis of a variety of biological samples, such as living cells. Up to now, it still remains a challenge to successfully decouple signals related to topography and reactivity. Furthermore, such delicate samples require careful adjustment of experimental parameters, such as scan velocity. The present study proposes a method to extract a substrate's kinetic rate by numerical modeling and experimental high speed constant height SECM imaging. This is especially useful for the determination of substrates with unknown surface reaction kinetics and large topographical features. To make this approach applicable to soft cell samples, which cannot be imaged at high velocity, a nonlinear fit strategy is presented to obtain kinetic rate values also under slow scan velocity conditions.
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Técnicas de Química Analítica/métodos , Microscopía Electroquímica de Rastreo , Polímeros/química , Electrodos , Cinética , Platino (Metal)/químicaRESUMEN
Scanning electrochemical microscopy (SECM) is increasingly applied to study and image live cells. Quantitative analyses of biological systems, however, still remain challenging. In the presented study, single human adenocarcinoma cervical cancer cells are electrochemically investigated by means of SECM. The target cell's electrochemical response is observed over time under the influence of green tea catechins (GTC), which are suggested to offer chemopreventive and therapeutic effects on cancer. The electrochemical response of living target cells is measured experimentally and quantified in an apparent heterogeneous rate constant by using a numerical model, based on forced convection during high speed SECM imaging. The beneficial effect of GTC on cancer cells could be confirmed by SECM, and the presented study shows an alternative approach toward unraveling the mechanisms involved during inhibition of carcinogenesis.
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Catequina/química , Técnicas de Química Analítica/métodos , Electroquímica , Microscopía Electroquímica de Rastreo , Neoplasias/patología , Carcinogénesis/efectos de los fármacos , Catequina/farmacología , Supervivencia Celular/efectos de los fármacos , Células HeLa , Humanos , Cinética , Té/químicaRESUMEN
The emergence of resistance to multiple unrelated chemotherapeutic drugs impedes the treatment of several cancers. Although the involvement of ATP-binding cassette transporters has long been known, there is no in situ method capable of tracking this transporter-related resistance at the single-cell level without interfering with the cell's environment or metabolism. Here, we demonstrate that scanning electrochemical microscopy (SECM) can quantitatively and noninvasively track multidrug resistance-related protein 1-dependent multidrug resistance in patterned adenocarcinoma cervical cancer cells. Nonresistant human cancer cells and their multidrug resistant variants are arranged in a side-by-side format using a stencil-based patterning scheme, allowing for precise positioning of target cells underneath the SECM sensor. SECM measurements of the patterned cells, performed with ferrocenemethanol and [Ru(NH3)6](3+) serving as electrochemical indicators, are used to establish a kinetic "map" of constant-height SECM scans, free of topography contributions. The concept underlying the work described herein may help evaluate the effectiveness of treatment administration strategies targeting reduced drug efflux.
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Técnicas de Cultivo de Célula/métodos , Resistencia a Múltiples Medicamentos/fisiología , Microscopía de Sonda de Barrido/métodos , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/metabolismo , Femenino , Compuestos Ferrosos , Células HeLa , Humanos , Microelectrodos , Microscopía Fluorescente , Microscopía de Sonda de Barrido/instrumentaciónRESUMEN
Cancer cell multidrug resistance is a molecular signature that highly influences the outcome of chemotherapy treatment and for which there is currently no robust method to monitor in vitro its activity. Herein, we demonstrate that ferrocenemethanol (FcCH(2)OH) and its oxidized form ([FcCH(2)OH](+)) affect the redox state of cancer cells. Specifically, the interaction of FcCH(2)OH with the glutathione couple (GSH/GSSG) is shown in human adenocarcinoma cervical cancer cells HeLa and a multidrug resistant variant overexpressing the multidrug resistant associated protein 1 (MRP1) using bioanalytical techniques, such as flow cytometry and fluorescence microscopy. It is further demonstrated that the differential response to FcCH(2)OH in multidrug-resistant cells is in part due to MRP1's unspecific efflux. Scanning electrochemical microscopy confirmed the interaction between FcCH(2)OH and the cells, and the differential response was observed to depend on MRP1 expression. This newly established relation between FcCH(2)OH/[FcCH(2)OH](+), GSH/GSSG and multidrug resistance in human cancer cells enables than the acquisition of scanning electrochemical microscopy images.