| 1. |
- Fuoco, Tiziana, PhD, 1986-, et al.
(författare)
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Capturing the Real-Time Hydrolytic Degradation of a Library of Biomedical Polymers by Combining Traditional Assessment and Electrochemical Sensors
- 2021
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 22:2, s. 949-960
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Tidskriftsartikel (refereegranskat)abstract
- We have developed an innovative methodology to overcome the lack of techniques for real-time assessment of degradable biomedical polymers at physiological conditions. The methodology was established by combining polymer characterization techniques with electrochemical sensors. The in vitro hydrolytic degradation of a series of aliphatic polyesters was evaluated by following the molar mass decrease and the mass loss at different incubation times while tracing pH and L-lactate released into the incubation media with customized miniaturized electrochemical sensors. The combination of different analytical approaches provided new insights into the mechanistic and kinetics aspects of the degradation of these biomedical materials. Although molar mass had to reach threshold values for soluble oligomers to be formed and specimens' resorption to occur, the pH variation and L-lactate concentration were direct evidence of the resorption of the polymers and indicative of the extent of chain scission. Linear models were found for pH and released L-lactate as a function of mass loss for the Llactide-based copolymers. The methodology should enable the sequential screening of degradable polymers at physiological conditions and has potential to be used for preclinical material's evaluation aiming at reducing animal tests.
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| 2. |
- Aref, Mohaddeseh, et al.
(författare)
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Potentiometric pH Nanosensor for Intracellular Measurements: Real-Time and Continuous Assessment of Local Gradients
- 2021
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 93:47, s. 15744-15751
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Tidskriftsartikel (refereegranskat)abstract
- We present a pH nanosensor conceived for single intracellular measurements. The sensing architecture consisted of a two-electrode system evaluated in the potentiometric mode. We used solid-contact carbon nanopipette electrodes tailored to produce both the indicator (pH nanosensor) and reference electrodes. The indicator electrode was a membrane-based ion-selective electrode containing a receptor for hydrogen ions that provided a favorable selectivity for intracellular measurements. The analytical features of the pH nanosensor revealed a Nernstian response (slope of -59.5 mV/pH unit) with appropriate repeatability and reproducibility (variation coefficients of <2% for the calibration parameters), a fast response time (<5 s), adequate medium-term drift (0.7 mV h(-)(1)), and a linear range of response including physiological and abnormal cell pH levels (6.0-8.5). In addition, the position and configuration of the reference electrode were investigated in cell-based experiments to provide unbiased pH measurements, in which both the indicator and reference electrodes were located inside the same cell, each of them inside two neighboring cells, or the indicator electrode inside the cell and the reference electrode outside of (but nearby) the studied cell. Finally, the pH nanosensor was applied to two cases: (i) the tracing of the pH gradient from extra-to intracellular media over insertion into a single PC12 cell and (ii) the monitoring of variations in intracellular pH in response to exogenous administration of pharmaceuticals. It is anticipated that the developed pH nanosensor, which is a label-free analytical tool, has high potential to aid in the investigation of pathological states that manifest in cell pH misregulation, with no restriction in the type of targeted cells.
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| 3. |
- Cuartero, Maria, PhD, 1984-
(författare)
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Electrochemical sensors for in-situ measurement of ions in seawater
- 2021
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 334
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Tidskriftsartikel (refereegranskat)abstract
- In the current water monitoring panorama, certain benefits are expected to arise when the modus operandum of analysis shifts from sampling-based to purely in-situ approaches. Since the appearance of the first submersible conductivity-temperature-depth (CTD) probe in the 80 s, clear efforts to move towards decentralized strategies have been reported in the literature, with some having even been brought to the stage of fruitful commercialization. Among the portfolio of available analytical techniques, only a handful of approaches offer clear potential for implementation in submersible devices, in terms of adequate analytical features, autonomy, feasibility of miniaturization, and ease of portability. Electrochemical sensors have demonstrated excellent characteristics for this purpose, particularly in the detection of ions. The present review analyses electrochemical sensors that have shown an aptitude for in-situ measurements of ions, including trace metals, nutrients, and carbon species in seawater. The previous 5 years have been selected as the main period for review, although in some instances comment is made upon earlier contributions to the field or commercialized devices, where these are deemed to exemplify crucial technological advancements. There is a notable lack of electrochemical sensors being deployed in in-situ applications, and this scarcity is even more stark when seawater is considered: only a very few cases have been demonstrated under such challenging conditions. With the aim of providing inspiration towards genuine advances in the field of in-situ seawater analysis, this work also highlights some laboratory scale research as well as studies concerning other environmental waters than seawater.
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| 4. |
- Garcia-Guzman, Juan Jose, et al.
(författare)
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Microneedle based electrochemical (Bio)Sensing : Towards decentralized and continuous health status monitoring
- 2021
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Ingår i: TrAC. Trends in analytical chemistry. - : Elsevier BV. - 0165-9936 .- 1879-3142. ; 135
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Forskningsöversikt (refereegranskat)abstract
- Microneedle (MN) based electrochemical (bio)sensing has become a growing field within the discipline of analytical chemistry as a result of its unique capacity for continuous, decentralized health status monitoring. There are two significant advantages to this exclusive feature: i) the ability to directly analyze interstitial fluid (ISF), a body fluid with a similar enough composition to plasma (and blood) to be considered a plentiful source of information related to biologically relevant molecules and biomarkers; and ii) the capacity to overcome some of the major limitations of blood analysis including painful extraction, high interferant concentrations, and incompatibility with diagnosis of infants (and especially newborns). Recent publications have demonstrated important advancements in electrochemical MN sensor technology, among which are included new MN fabrication methods and various modification strategies, providing different architectures and allowing for the integration of electronics. This versatility highlights the undeniable need for interdisciplinary efforts towards tangible progress in the field. In a context evidently dominated by glucose sensing, which is slowly being expanded towards other analytes, the following crucial questions arise: to what extent are electrochemical MN (bio)sensors a reliable analytical tool for continuous ISF monitoring? Which is the best calibration protocol to be followed for in vivo assays? Which strategies can be employed to protect the sensing element during skin penetration? Is there an appropriate validation methodology to assess the accuracy of electrochemical MN (bio)sensors? How significant is the distinction between successful achievements in the laboratory and the real commercial feasibility of products? This paper aims to reflect on those previous questions while reviewing the progress of electrochemical MN (bio)sensors in the last decade with a focus on the analytical aspects. Overall, we describe the current state of electrochemical MN (bio)sensors, the benefits and challenges associated to ISF monitoring, as well as key features (and bottlenecks) regarding its implementation for in vivo assays.
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| 5. |
- Garcia-Guzman, Juan Jose, et al.
(författare)
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Toward In Vivo Transdermal pH Sensing with a Validated Microneedle Membrane Electrode
- 2021
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Ingår i: ACS Sensors. - : American Chemical Society (ACS). - 2379-3694. ; 6:3, s. 1129-1137
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Tidskriftsartikel (refereegranskat)abstract
- We present herein the most complete characterization of microneedle (MN) potentiometric sensors for pH transdermal measurements for the time being. Initial in vitro assessment demonstrated suitable analytical performances (e.g., Nernstian slope, linear range of response from 8.5 to 5.0, and fast response time) in both buffer media and artificial interstitial fluid (ISF). Excellent repeatability and reproducibility together with adequate selectivity and resiliency facilitate the appropriateness of the new pH MN sensor for transdermal ISF analysis in healthcare. The ability to resist skin insertions was evaluated in several ex vivo setups using three different animal skins (i.e., chicken, pork, and rat). The developed pH MN sensor was able to withstand from 5 to 10 repetitive insertions in all the skins considered with a minimal change in the calibration graph (<3% variation in both slope and intercept after the insertions). Ex vivo pH measurements were validated by determining the pH with the MN sensor and a commercial pH electrode in chicken skin portions previously conditioned at several pH values, obtaining excellent results with an accuracy of <1% and a precision of <2% in all cases. Finally, pH MN sensors were applied for the very first time to transdermal measurements in rats together with two innovative validation procedures: (i) measuring subcutaneous pH directly with a commercial pH microelectrode and (ii) collecting ISF using hollow MNs and then the pH measurement of the sample with the pH microelectrode. The pH values obtained with pH MN sensors were statistically more similar to subcutaneous measurements, as inferred by a paired sample t-test at 95% of confidence level. Conveniently, the validation approaches could be translated to other analytes that are transdermally measured with MN sensors.
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| 6. |
- Liu, Yujie, et al.
(författare)
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Semi-empirical treatment of ionophore-assisted ion-transfers in ultrathin membranes coupled to a redox conducting polymer
- 2021
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 388, s. 138634-
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Tidskriftsartikel (refereegranskat)abstract
- Applying spectroelectrochemistry to all-solid-state electrodes composed of poly(3-octylthiophene) (POT) and an ultrathin ion-selective membrane on top, it is possible to monitor the dynamic charge transfer (CT) in POT when this event is coupled to ion transfers (ITs) promoted by the absence/presence of a se-lective ionophore in the membrane. Herein, we report on a combination of empirical and theoretical ev-idence revealing that different molar ratios of the ionophore and the cation exchanger in the membrane result in the modulation of non-assisted and assisted ITs of different stoichiometries. This occurs upon the same anodic voltammetric scan. The use of the developed theory together with Sigmoidal & minus;Boltzmann fittings of the experimental dynamic absorbance observed in the POT film permits calculating voltammo-grams with different ITs. An easy semi-empirical treatment additionally provides the calculation of bind-ing constants related to the assisted transfers. Furthermore, the approach is suitable for both preferred and non-preferred ions by the ionophore, which additionally leads to the estimation of the selectivity profile of the POT-membrane system. The extra discovery about the number of electrons associated to the CT in the POT film is expected to propitiate further research towards maximizing peak resolution in the voltammetric experiments. In this context, the developed theory would help in future steps to-wards the prediction of voltammetric responses for multi-ionophore membranes backside contacted with new redox materials, prospecting hence new electrodes for multi-ion detection with optimized analytical features.
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| 7. |
- Molina Osorio, Andres, et al.
(författare)
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Modelling electrochemical modulation of ion release in thin-layer samples
- 2021
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Ingår i: JOURNAL OF ELECTROANALYTICAL CHEMISTRY. - : Elsevier BV. - 1572-6657. ; 903, s. 115851-
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we present a model based on the finite element approach to describe the electrochemically controlled release of ions from a redox-active film into a sample confined to a thin-layer spatial domain. The model includes the effect of interfacial charge transfer kinetics and 1D-diffusion treatment for an electron transfer-ion transfer (ET-IT) coupled reaction. More in detail, the oxidation of the redox-active film (ET) involves an ion release to an aqueous phase (IT). The dynamic concentration of the released ion is calculated when the ET-IT reaction proceeds under potentiostatic control, and the effect of the thickness of each phase (i.e., film or aqueous) on the diffusion profile is analyzed. The model is experimentally validated for the particular case in which oxidation of a thin film of polyaniline (PANI, 10 mu m in thickness) is linked to the release of protons from the film into an electrolyte solution. The proton release produces certain pH changes in the electrolyte that are monitored by a pH sensor located at 330 mu m from the PANI film. The charge associated with the proton release is related to the dynamic concentration of protons in the electrolyte through pH-coulograms that agree with the theoretical predictions. Overall, the model can reproduce the general behavior of the experimental proton pump and provides key insights into the functioning mechanism of electrochemical systems where redox and ion transfer reactions are coupled.
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| 8. |
- Van Hoovels, Kevin, et al.
(författare)
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Can Wearable Sweat Lactate Sensors Contribute to Sports Physiology?
- 2021
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Ingår i: ACS Sensors. - : American Chemical Society (ACS). - 2379-3694. ; 6:10, s. 3496-3508
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Forskningsöversikt (refereegranskat)abstract
- The rise of wearable sensors to measure lactate content in human sweat during sports activities has attracted the attention of physiologists given the potential of these "analytical tools" to provide real-time information. Beyond the assessment of the sensing technology per se, which, in fact, has not rigorously been validated yet in controlled conditions, there are many open questions about the true usefulness of such wearable sensors in real scenarios. On the one hand, the evidence for the origin of sweat lactate (e.g., via the sweat gland, derivation from blood, or other alternative mechanisms), its high concentration (1-25 mM or even higher) compared to levels in the blood, and the possible correlation between different biofluids (particularly blood) is rather contradictory and generates vivid debate in the field. On the other hand, it is important to point out that accurate detection of sweat lactate is highly dependent on the procedure used to collect and/or reach the fluid, and this can likely explain the large discrepancies reported in the literature. In brief, this paper provides our vision of the current state of the field and a thoughtful evaluation of the possible reasons for present controversies, together with an analysis of the impact of wearable sweat lactate sensors in the physiological context. Finally, although there is not yet overwhelming scientific evidence to provide an unequivocal answer to whether wearable sweat lactate sensors can contribute to sports physiology, we still understand the importance to bring this challenging question up-front to create awareness and guidance in the development, validation, and implementation of wearable sensors.
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| 9. |
- Wang, Qianyu, et al.
(författare)
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Electrochemical biosensor for glycine detection in biological fluids
- 2021
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Ingår i: Biosensors & bioelectronics. - : Elsevier BV. - 0956-5663 .- 1873-4235. ; 182
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Tidskriftsartikel (refereegranskat)abstract
- We present herein the very first amperometric biosensor for the quantitative determination of glycine in diverse biological fluids. The biosensor is based on a novel quinoprotein that catalyzes the oxidation of glycine with high specificity. This process is coupled to the redox conversion of Prussian blue in the presence of hydrogen peroxide originating from the enzymatic reaction. The optimized tailoring of the biosensor design consists of the effective encapsulation of the quinoprotein in a chitosan matrix with the posterior addition of an outer Nafion layer, which is here demonstrated to suppress matrix interference. This is particularly important in the case of ascorbic acid, which is known to influence the redox behavior of the Prussian blue. The analytical performance of the biosensor demonstrates fast response time (<7 s), acceptable reversibility, reproducibility, and stability (<6% variation) as well as a wide linear range of response (25?500 ?M) that covers healthy (and even most unhealthy) physiological levels of glycine in blood/serum, urine and sweat. A total of 6 real samples from healthy patients and animals were analyzed: two serum, two urine and two sweat samples. The results were validated via commercially available fluorescence kit, displaying discrepancy of less than 9% in all the samples. The unique analytical features and effortless preparation of the new glycine biosensor position it at the forefront of current technologies towards decentralized clinical applications and sport performance monitoring.
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| 10. |
- Wiorek, Alexander, et al.
(författare)
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Reagentless Acid–Base Titration for Alkalinity Detection in Seawater
- 2021
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 93:42, s. 14130-14137
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we report on a reagentless electroanalytical methodology for automatized acid–base titrations of water samples that are confined into very thin spatial domains. The concept is based on the recent discovery from our group (Wiorek, A. Anal. Chem. 2019, 91, 14951−14959), in which polyaniline (PANI) films were found to be an excellent material to release a massive charge of protons in a short time, achieving hence the efficient (and controlled) acidification of a sample. We now demonstrate and validate the analytical usefulness of this approach with samples collected from the Baltic Sea: the titration protocol indeed acts as an alkalinity sensor via the calculation of the proton charge needed to reach pH 4.0 in the sample, as per the formal definition of the alkalinity parameter. In essence, the alkalinity sensor is based on the linear relationship found between the released charge from the PANI film and the bicarbonate concentration in the sample (i.e., the way to express alkalinity measurements). The observed alkalinity in the samples presented a good agreement with the values obtained by manual (classical) acid–base titrations (discrepancies <10%). Some crucial advantages of the new methodology are that titrations are completed in less than 1 min (end point), the PANI film can be reused at least 74 times over a 2 week period (<5% of decrease in the released charge), and the utility of the PANI film to even more decrease the final pH of the sample (pH ∼2) toward applications different from alkalinity detection. Furthermore, the acidification can be accomplished in a discrete or continuous mode depending on the application demands. The new methodology is expected to impact the future digitalization of in situ acid–base titrations to obtain high-resolution data on alkalinity in water resources.
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| 11. |
- Xu, Kequan
(författare)
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Electrochemical detection of trace metals: from traditional techniques to new ultrathin membrane electrodes
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Accurate detection of trace metals in environmental waters is an analytical challenge that is still open for the time being. The current state of the field reveals the predominance of the so-called hanging mercury drop electrode (HMDE) for multi-metal detection by means of anodic stripping voltammetry (ASV) readout. Being aware of the high toxicity of mercury and the high risk of a serious environmental footprint when water measurements are performed with the HMDE, in the past years, the electrochemistry field has rapidly moved towards the provision of tangible alternatives. Yet, none of the proposed methodologies has reached appropriate maturation and/or analytical features to substitute the use of the HMDE in the detection of trace metal ions in water.The investigations presented in this thesis are framed within the direction of new analytical strategies for the detection of trace metals in water, with special focus on the silver ion (Ag+). Voltammetric ion-selective electrodes (ISEs) with a working mechanism conceived on the basis of interconnected charge-transfer (CT) and ion-transfer (IT) processes are selected for such purpose due to their unique characteristics towards decentralized measurements.The first chapter of the thesis aims to provide a general background about electrochemistry measurements of ions, providing special attention to all-solid-state voltammetric ISEs based on ultrathin membranes that provide the CT–IT mechanism. Fundaments about ASV and the use of the HMDE for trace metal detection are also revised. Of particular interest is the case of Ag+ determination, which is not fully addressed with the HMDE. Accordingly, the state-of-the-art of electrochemical analysis of trace Ag+ has been established (Paper I).The second chapter shows the experimental details and the third chapter presents and discusses all the results obtained in this thesis.The first section is about a new analytical strategy for nanomolar detection of Ag+ in waters by coupling a silver-selective electrode (AgSE) based on a CT–IT mechanism with IT stripping voltammetry readout (Paper II). Specifically, the IT occurs via providing the CT process in electrodes that are modified with a redox-active conductive polymer and an ultrathin silver-selective membrane placed on top. Thus, the CT–IT tandem in voltammetric ISEs is unprecedently demonstrated for the detection of Ag+ in different water samples.The second section is based on the improvement of the limit of detection of the developed AgSE to detect sub-nanomolar concentration of Ag+ even in the presence of high interference levels, e.g., sodium ion (Paper III). Through the reduction of the total ion-exchange capacity of the ultrathin membrane, it is possible to increase the effectiveness towards the intake of Ag+ versus sodium ions (Na+) when IT stripping voltammetry is applied. The resulting ISE displayed a limit of detection of 0.05 nM, with a linear range of response up to 10 nM and is successfully applied for the analysis of Ag+ in several water samples, including seawater.The third section presents the investigation of the HMDE for multi-metal detection at trace levels in soil waters while establishing the fundaments, features and controversies of the technique (Paper IV). The entire replacement of the HMDE will only occur when multi-metal trace detection is provided by a sole electrode or an electrode array able to provide similar analytical characteristics, which are collected in this thesis, while avoiding the use of mercury or any other pollutant in the electrode manufacturing.The fourth section inquiries the possibility of using voltammetric ISE based on interconnected CT–IT processes for other trace metals, in particular lead and copper ions (Pb2+ and Cu2+) (Paper V). Despite more work being necessary in that direction, preliminary insights have revealed the potential of the CT–IT technique developed in this thesis towards multi-metal detection either with the incorporation in the membrane of multiple ionophores with different selectivity profiles for each metal or with a multi-sensor array. Accordingly, the research work presented in this thesis has a strong potential towards future investigations in this direction.
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| 12. |
- Xu, Kequan, et al.
(författare)
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Electrochemical detection of trace silver
- 2021
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 374
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Tidskriftsartikel (refereegranskat)abstract
- Increasing utilization of silver and silver nanoparticles (AgNPs) in daily processes and products has led to a significant growth in scientific interest in methods for monitoring silver. In particular, the amount of silver ions (Ag +) released to the environment is known to have a detrimental effect on aquatic ecology, and thus some control actions have been implemented in recent years; for example, the manufacturing industry is now required to control and certify the quantity of AgNPs present in products. Electrochemical sensors are well suited to the task of silver monitoring due to several beneficial properties, including low costs, fast measurements, and facile adaptation to miniaturized, portable instrumentation. The predominant method for electrochemical silver determination involves potentiometric ion selective electrodes (ISEs) and voltammetric measurements. Reviewing the literature of the last ten years reveals significant improvements in the analytical performance of electrochemical sensors, mainly related to the development of new protocols, selective receptors, and electrode materials. Remarkably, ISEs with limits of detection (LOD) in the nanomolar range have been reported, employing careful control of ion fluxes across the membrane interfaces. What's more, sub-nanomolar LODs are attainable by stripping voltammetry using either ligand-based deposition strategies or thin layer membranes coupled to conducting polymers. Selectivity has also been optimized through the membrane composition of ISEs, with special focus on Ag+ ionophores. Furthermore, novel voltammetric methods allow for discrimination between Ag+ and AgNPs. However, there is still a dearth of studies applying such electrochemical sensors to on-site water analysis, and hence, further research is needed in order to translate these laboratory scale achievements to real-world contexts. Overall, this review describes the state-of-the-art in electrochemical silver detection, and provides a comprehensive description of those aspects contributing to the further development and improvement of analytical performance.
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| 13. |
- Xuan, Xing, et al.
(författare)
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Lactate Biosensing for Reliable On-Body Sweat Analysis
- 2021
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Ingår i: ACS Sensors. - : American Chemical Society (ACS). - 2379-3694. ; 6:7, s. 2763-2771
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Tidskriftsartikel (refereegranskat)abstract
- Wearable lactate sensors for sweat analysis are highly appealing for both the sports and healthcare fields. Electrochemical biosensing is the approach most widely used for lactate determination, and this technology generally demonstrates a linear range of response far below the expected lactate levels in sweat together with a high influence of pH and temperature. In this work, we present a novel analytical strategy based on the restriction of the lactate flux that reaches the enzyme lactate oxidase, which is immobilized in the biosensor core. This is accomplished by means of an outer plasticized polymeric layer containing the quaternary salt tetradodecylammonium tetrakis(4-chlorophenyl) borate (traditionally known as ETH500). Also, this layer prevents the enzyme from being in direct contact with the sample, and hence, any influence with the pH and temperature is dramatically reduced. An expanded limit of detection in the millimolar range (from 1 to 50 mM) is demonstrated with this new biosensor, in addition to an acceptable response time; appropriate repeatability, reproducibility, and reversibility (variations lower than 5% for the sensitivity); good resiliency; excellent selectivity; low drift; negligible influence of the flow rate; and extraordinary correlation (Pearson coefficient of 0.97) with a standardized method for lactate detection such as ion chromatography (through analysis of 22 sweat samples collected from 6 different subjects performing cycling or running). The developed lactate biosensor is suitable for on-body sweat lactate monitoring via a microfluidic epidermal patch additionally containing pH and temperature sensors. This applicability was demonstrated in three different body locations (forehead, thigh, and back) in a total of five on-body tests while cycling, achieving appropriate performance and validation. Moreover, the epidermal patch for lactate sensing is convenient for the analysis of sweat stimulated by iontophoresis in the subjects' arm, which is of great potential toward healthcare applications.
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