This article reviews recent advances and developments in the field of wearable sensors with emphasis on a subclass of these devices that are able to perform highly‐sensitive electrochemical analysis. ...Recent insights into novel fabrication methodologies and electrochemical techniques have resulted in the demonstration of chemical sensors able to augment conventional physical measurements (i.e. heart rate, EEG, ECG, etc.), thereby providing added dimensions of rich, analytical information to the wearer in a timely manner. Wearable electrochemical sensors have been integrated onto both textile materials and directly on the epidermis for various monitoring applications owing to their unique ability to process chemical analytes in a non‐invasive and non‐obtrusive fashion. In this manner, multi‐analyte detection can easily be performed, in real time, in order to ascertain the overall physiological health of the wearer or to identify potential offenders in their environment. Of profound importance is the development of an understanding of the impact of mechanical strain on textile‐ and epidermal (tattoo)‐based sensors and their failure mechanisms as well as the compatibility of the substrate employed in the fabrication process. We conclude this review with a retrospective outlook of the field and identify potential implications of this new sensing paradigm in the healthcare, fitness, security, and environmental monitoring domains. With continued innovation and detailed attention to core challenges, it is expected that wearable electrochemical sensors will play a pivotal role in the emergent body sensor networks arena.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
A novel implementation of an electrochemical sensors making use of Screen-Printed Electrodes (SPE) has been discussed. SPE's modified with Carbon-supported Platinum (Pt/C) and Gold (Au/C) were used ...to detect the three benzenediol isomers, Catechol (CC), Hydroquinone (HQ) and Resorcinol (RS) in acidic media using traditional electrochemical analytical methods such as Cyclic Voltammetry (CV), Chronoamperometry (CA) and Differential Pulse Voltammetry (DPV). Detection of each benzenediol in isolation was possible by CV measurements, and peak oxidation potentials for each isomer were noted. Simultaneous detection of more than one, or all analytes in the same solution was also observed through DPV, once again noting the peak oxidation potentials. Quantification limits were observed using CA's across concentration values ranging from close to saturation down to 1 mM for CC and HQ, and 100 nM for RS, until the recorded current values were nearly indistinguishable to a blank 1 M HCl solution containing no analyte(s), and also evaluating the maximum possible linear range of sensing. The analytes were introduced to the sensor elements in controlled amounts and the electrochemical responses of the sensor elements were recorded and processed. Measurements were repeated across two potentiostats to ensure reproducibility. With these results, successful detection of benzenediols in acidic environment was possible using modified SPE's, proving a potential viable mechanism for quick, simple and inexpensive Volatile Toxic Organic Compounds (VTOC) detection and monitoring.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A methodology is presented to develop tungsten-oxide based inks for screen-printing. Different amounts of tungsten oxide have been grown by co-precipitation on the surface of conducting ...microparticles. These modified particles have been formulated into inks, and electrodes have been screen-printed. The work describes the characterization of the materials using a range of techniques including XRD, SEM, as well as electrochemical and spectroscopic techniques. Thermal treatment of the co-precipited oxides changes their crystalline structure, increasing bandgap (from 2.48 eV to 2.87 eV) and worsening their electrochromic performance. Structures printed with untreated WO3-based materials display contrast ratios as high as 90 % in reflectance, and colour efficiencies between 30 and 40 cm2 C–1. Another important aspect is the pH stability of the oxide up to pH = 6.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•In this review, we highlight the preparation of conductive inks.•Low-cost conductive inks are attractive for electrochemistry.•Several strategies for electrodes preparation are ...addressed in this paper.
The monitoring of species of medical, environmental, and industrial interests has been urgently demanded. Several times, the necessity of point of care and/or point of use is important to obtain precise and rapid quantification, in which wearable and flexible disposable electrochemical sensors and biosensors have been great alternatives. In this context, a short review describing the main advances in the fabrication and development of conductive inks for the construction of miniaturized and disposable electrochemical devices is presented. Electrochemical devices developed from conductive inks have been an innovative system that promotes flexibility for the design of the electrodes. The growing increase in the number of researches regarding the development of inks is driven by the search for simplicity, low-cost, less waste generation, mass production, and environmentally friendly manufacturing methods. The present review focuses on alternative conductive inks and their compounds, binders, and conductive materials for electrochemistry. The binder such as varnishes, natural resins, and natural polymeric compounds will be presented, once they promote the dispersion of conductive material, as well as the adhesion on the substrate. Special attention is given to conductive materials. We highlight some nanostructured materials such as platinum, silver, and gold nanoparticles, due to their great conductivity and extensive use to develop electrochemical sensors. Inks and electrodes from carbon-based materials are also discussed, such as graphite, carbon nanotubes, carbon black, and graphene. The biocompatibility of these materials, especially important for wearable sensors, will also be approached. Finally, we present new perspectives on the development of sensors and biosensors using conductive inks.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Screen-printed electrodes modified with nanomaterials provide better analytical features.•Paper based electrochemical devices provide easy and cost effective analyses.•Label-free innovative ...electrochemical immunosensors as screening methods to detect important metabolites.•Novel DNA-based electrochemical disposable sensors: new devices to measure low concentrations of clinical markers.
This review addresses recent advances in the development of screen-printed electrode based biosensors modified with different nanomaterials such as carbon nanotubes, graphene, metallic nanoparticles as gold, silver and magnetic nanoparticles, and mediator nanoparticles (Prussian Blue, Cobalt Phthalocyanine, etc.), coupled with biological recognition elements such as enzymes, antibodies, DNA and aptamers to obtain probes with improved analytical features. Examples of clinical applications are illustrated, together with examples of paper-based electrochemical devices, of multiple detections using arrays of screen printed electrodes, and of the most recent developments in the field of wearable biosensors. Also the use of smartphones as final detectors is briefly depicted.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•There has been increasing interest in disposable sensors in pharmaceutical analysis.•Various applications of screen-printed electrodes (SPEs) in pharmaceutical analysis are discussed.•SPEs used for ...the analysis of pharmaceutical residues in different matrices are described.•The basic fabrication and recent advances in the design of SPEs are presented.•Different SPE modification procedures are described.
Miniaturization is crucial for the development of the current analytical tools. Several types of disposable electrochemical sensors based on the technology of screen printing have been designed for economic and practical feasibility. In the past few decades, several advances have been made in the setup and assembly of printing materials for screen-printed electrodes (SPEs). Due to their excellent material properties, simplicity, disposability, and short response times, SPEs have been efficiently used for rapid in situ analysis. This review aims to describe the elementary fabrication principles, the different designs of SPEs, and the different analytical methods based on SPEs. We particularly focus on the electrochemical application of SPEs in pharmaceutical analysis, including the determination of drugs, metabolites, and degradation products in different matrices.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
This short article overviews the use of screen-printed electrodes (SPEs) in the field of electroanalysis and compares their application against traditional laboratory based analytical techniques. ...Electroanalysis coupled with SPEs can offer low-cost, precise, sensitive, rapid, quantitative information and laboratory equivalent results. The combined use of SPEs and electroanalysis reduces the need of sample transportation and preparation to a centralised laboratory allowing experimentalists to perform the measurements where they are needed the most. We first introduce the basic concepts and principles of analytical techniques to the reader, with particular attention to electroanalysis, and then discuss the application of SPEs to common analytical targets such as food, environmental, forensics, cancer biomarkers and pathogenic monitoring and sensing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This work reports the determination of 5 neonicotinoid pesticides (Clothianidin, Imidacloprid, Thiamethoxam, Nitenpyram and Dinotefuran) in water samples by cathodic differential pulse (DP) ...voltammetry at screen‐printed disposable sensors featuring a sputtered bismuth thick‐film working electrode, a Ag reference electrode and a carbon counter electrode. The performance of the bismuth thick‐film electrodes was compared to that of a home‐made bismuth thin‐film electrode and a bismuth‐bulk electrode. The electrodes were further characterized by electrochemical and optical techniques. The effect of the pH of the supporting electrolyte on the DP reduction currents of the 5 pesticides was studied. The limits of quantification (LOQs) in 4 water matrices (distilled water, tap water, mineral water and surface water) were in the range 0.76 to 2.10 mg L−1 but severe matrix effects were observed in the analysis of mineral and, especially, surface water samples. Using a solid‐phase extraction (SPE) procedure using Lichrolut EN cartridges and elution with methanol, the matrix effects were substantially reduced and the LOQs were in the range 9 to 17 µg L−1. The recoveries of surface water samples spiked with the 5 target neonicotinoids at two concentration levels (20 and 50 µg L−1) were in the range 89 to 109 % and the % relative standard deviations ranged from 4.3 to 7.2 %.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Early detection of cancer increases the possibility for an adequate and successful treatment of the disease. Therefore, in this work, a disposable electrochemical immunosensor for the front-line ...detection of the ExtraCellular Domain of the Human Epidermal growth factor Receptor 2 (HER2-ECD), a breast cancer biomarker, in a simple and efficient manner is presented. Bare screen-printed carbon electrodes were selected as the transducer onto which a sandwich immunoassay was developed. The affinity process was detected through the use of an electroactive label, core/shell CdSe@ZnS Quantum Dots, by differential pulse anodic stripping voltammetry in a total time assay of 2 h, with an actual hands-on time of less than 30 min. The proposed immunosensor responded linearly to HER2-ECD concentration within a wide range (10–150 ng/mL), showing acceptable precision and a limit of detection (2.1 ng/mL, corresponding to a detected amount (sample volume = 40 μL) of 1.18 fmol) which is about 7 times lower than the established cut-off value (15 ng/mL). The usefulness of the developed methodology was tested through the analysis of spiked human serum samples. The reliability of the presented biosensor for the selective screening of HER2-ECD was confirmed by analysing another breast cancer biomarker (CA15-3) and several human serum proteins.
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•Detection of cancer biomarkers in biological fluids is useful for early diagnosis.•An electrochemical immunosensor was developed for HER2-ECD.•Quantum dots were used as detection label.•The assay was selective towards the target biomarker.•The assay was successfully tested in the analysis of human serum.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Triple-negative breast cancer (TNBC) is one of the most aggressive and lethal types of BC, affecting mostly young women and its diagnosis is difficult and requires invasive methods, such as tissue ...biopsy which is painful and expensive. However, nowadays liquid biopsy is emerging as a great tool for determining blood-circulating species associated to cancer and to its early diagnosis and prognosis. Among the species, the relevance of microRNAs (miRNAs) has been highlighted as promising biomarker, and miRNA-652 has been associated with TNBC as it promotes the growth and migration of cancer cells. In this work we designed and characterized a paper-based electrochemical device capable of recognizing and quantifying miRNA-652, as future tool for liquid biopsy in TNBC. The device consists of an AuNP-modified office paper-based screen-printed electrode customized with an anti-miRNA probe for the selective recognition of miRNA-652. All the experimental parameters have been carefully evaluated, and the platform allowed to detect miRNA-652 in standard solution and human serum down to 0.4 nM, with a satisfactory repeatability of about 6 and 3 % respectively. The selectivity presence of other miRNA sequences was satisfactory demonstrated. In addition, we demonstrated the effectiveness of pre-concentration of miRNA by coupling the office paper-based electrode with an external disk made by chromatographic paper: the detection limit has been improved of 10-fold without the use of complex/expensive procedures. The presented manuscript represents an important step towards the development of a non-invasive, sensitive and TNBC-specific diagnostic platform that could improve patients' prognosis and quality of life, ulteriorly improved with pre-concentering properties of frugal supports as the external chromatographic paper-based ones.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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