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Micromachines May 2016Electrochemistry is ideally suited to serve as a detection mechanism in miniaturized analysis systems. A significant hurdle can, however, be the implementation of... (Review)
Review
Electrochemistry is ideally suited to serve as a detection mechanism in miniaturized analysis systems. A significant hurdle can, however, be the implementation of reliable micrometer-scale reference electrodes. In this tutorial review, we introduce the principal challenges and discuss the approaches that have been employed to build suitable references. We then discuss several alternative strategies aimed at eliminating the reference electrode altogether, in particular two-electrode electrochemical cells, bipolar electrodes and chronopotentiometry.
PubMed: 30404256
DOI: 10.3390/mi7050081 -
ACS Omega Aug 2020The acid base protonation equilibria of -acetylcysteine (Nac) and its equilibrium constants in water solutions were determined by the Hyperquad 2008 software assessment...
The acid base protonation equilibria of -acetylcysteine (Nac) and its equilibrium constants in water solutions were determined by the Hyperquad 2008 software assessment from the pH potentiometry data, which provides a diversity of statistics presentations. The effect of a number of organic solvents on the acid base protonation processes was also examined. The solution equilibria of -acetylcysteine (Nac) were studied at = 298.15 K in water ( ) + organic liquid mixtures [100 = 0, 20, 40, 60, and 80%] with an ionic strength of = 0.16 mol·dm NaNO. Also, the organic solvent's influence was studied based on the Kamlet-Taft linear solvation energy relationship. The experimental results were compared with theoretical ones obtained via the Gaussian 09 calculation computer program. The protonation equilibria of Nac were found to be important in the progress of separation systems in aqueous and non-aqueous ionic solutions. Nac showed a likely good metal dibasic chelating bioligand as the DFT calculations proved two binding sites. Spectrophotometry evaluation was also done for -acetylcysteine bioligands at various pH values in water solutions then its absorbance ratio was measured.
PubMed: 32803054
DOI: 10.1021/acsomega.0c02080 -
Biochemistry. Biokhimiia Oct 2023Heme-copper respiratory oxidases are highly efficient molecular machines. These membrane enzymes catalyze the final step of cellular respiration in eukaryotes and many... (Review)
Review
Heme-copper respiratory oxidases are highly efficient molecular machines. These membrane enzymes catalyze the final step of cellular respiration in eukaryotes and many prokaryotes: the transfer of electrons from cytochromes or quinols to molecular oxygen and oxygen reduction to water. The free energy released in this redox reaction is converted by heme-copper respiratory oxidases into the transmembrane gradient of the electrochemical potential of hydrogen ions ). Heme-copper respiratory oxidases have a unique mechanism for generating H+, namely, a redox-coupled proton pump. A combination of direct electrometric method for measuring the kinetics of membrane potential generation with the methods of prestationary kinetics and site-directed mutagenesis in the studies of heme-copper oxidases allows to obtain a unique information on the translocation of protons inside the proteins in real time. The review summarizes the data of studies employing time-resolved electrometry to decipher the mechanisms of functioning of these important bioenergetic enzymes.
Topics: Electron Transport Complex IV; Heme; Membrane Potentials; Oxidoreductases; Oxidation-Reduction; Protons; Ceruloplasmin; Oxygen
PubMed: 38105021
DOI: 10.1134/S0006297923100085 -
Journal of Neuroengineering and... Aug 2020Traumatic Brain Injury (TBI) is a leading cause of fatality and disability worldwide, partly due to the occurrence of secondary injury and late interventions. Correct...
BACKGROUND
Traumatic Brain Injury (TBI) is a leading cause of fatality and disability worldwide, partly due to the occurrence of secondary injury and late interventions. Correct diagnosis and timely monitoring ensure effective medical intervention aimed at improving clinical outcome. However, due to the limitations in size and cost of current ambulatory bioinstruments, they cannot be used to monitor patients who may still be at risk of secondary injury outside the ICU.
METHODS
We propose a complete system consisting of a wearable wireless bioinstrument and a cloud-based application for real-time TBI monitoring. The bioinstrument can simultaneously record up to ten channels including both ECoG biopotential and neurochemicals (e.g. potassium, glucose and lactate), and supports various electrochemical methods including potentiometry, amperometry and cyclic voltammetry. All channels support variable gain programming to automatically tune the input dynamic range and address biosensors' falling sensitivity. The instrument is flexible and can be folded to occupy a small space behind the ear. A Bluetooth Low-Energy (BLE) receiver is used to wirelessly connect the instrument to a cloud application where the recorded data is stored, processed and visualised in real-time. Bench testing has been used to validate device performance.
RESULTS
The instrument successfully monitored spreading depolarisations (SDs) - reproduced using a signal generator - with an SNR of 29.07 dB and NF of 0.26 dB. The potentiostat generates a wide voltage range from -1.65V to +1.65V with a resolution of 0.8mV and the sensitivity of the amperometric AFE was verified by recording 5 pA currents. Different potassium, glucose and lactate concentrations prepared in lab were accurately measured and their respective working curves were constructed. Finally,the instrument achieved a maximum sampling rate of 1.25 ksps/channel with a throughput of 105 kbps. All measurements were successfully received at the cloud.
CONCLUSION
The proposed instrument uniquely positions itself by presenting an aggressive optimisation of size and cost while maintaining high measurement accuracy. The system can effectively extend neuroelectrochemical monitoring to all TBI patients including those who are mobile and those who are outside the ICU. Finally, data recorded in the cloud application could be used to help diagnosis and guide rehabilitation.
Topics: Biosensing Techniques; Brain Chemistry; Brain Injuries, Traumatic; Electrocorticography; Humans; Male; Monitoring, Ambulatory; Neurophysiological Monitoring
PubMed: 32825829
DOI: 10.1186/s12984-020-00742-x -
Materials (Basel, Switzerland) Dec 2023Tin determination allows for the monitoring of pollution and assessment of the impact of human activities on the environment. The determination of tin in the environment... (Review)
Review
Tin determination allows for the monitoring of pollution and assessment of the impact of human activities on the environment. The determination of tin in the environment is crucial for the protection of human health and ecosystems, and for maintaining sustainability. Tin can be released into the environment from various sources, such as industry, transportation, and electronic waste. The concentration of tin in the environment can be determined by different analytical methods, depending on the form of tin present and the purpose of the analysis. The choice of an appropriate method depends on the type of sample, concentration levels, and the available instrumentation. In this paper, we have carried out a literature review of electrochemical methods for the determination of tin. Electrochemical methods of analysis such as polarography, voltammetry, and potentiometry can be used for the determination of tin in various environmental samples, as well as in metal alloys. The detection limits and linearity ranges obtained for the determination of tin by different electrochemical techniques are collected and presented. The influence of the choice of base electrolyte and working electrode on signals is also presented. Practical applications of the developed tin determination methods in analyzing real samples are also summarized.
PubMed: 38138688
DOI: 10.3390/ma16247545 -
Ground Water Sep 2021
Topics: Groundwater; Potentiometry
PubMed: 34272877
DOI: 10.1111/gwat.13123 -
Lab on a Chip May 2017The demand for wearable sensors has grown rapidly in recent years, with increasing attention being given to epidermal chemical sensing. Here, we present the first...
The demand for wearable sensors has grown rapidly in recent years, with increasing attention being given to epidermal chemical sensing. Here, we present the first example of a fully integrated eyeglasses wireless multiplexed chemical sensing platform capable of real-time monitoring of sweat electrolytes and metabolites. The new concept has been realized by integrating an amperometric lactate biosensor and a potentiometric potassium ion-selective electrode into the two nose-bridge pads of the glasses and interfacing them with a wireless electronic backbone placed on the glasses' arms. Simultaneous real-time monitoring of sweat lactate and potassium levels with no apparent cross-talk is demonstrated along with wireless signal transduction. The electrochemical sensors were screen-printed on polyethylene terephthalate (PET) stickers and placed on each side of the glasses' nose pads in order to monitor sweat metabolites and electrolytes. The electronic backbone on the arms of the glasses' frame offers control of the amperometric and potentiometric transducers and enables Bluetooth wireless data transmission to the host device. The new eyeglasses system offers an interchangeable-sensor feature in connection with a variety of different nose-bridge amperometric and potentiometric sensor stickers. For example, the lactate bridge-pad sensor was replaced with a glucose one to offer convenient monitoring of sweat glucose. Such a fully integrated wireless "Lab-on-a-Glass" multiplexed biosensor platform can be readily expanded for the simultaneous monitoring of additional sweat electrolytes and metabolites.
Topics: Biosensing Techniques; Electrolytes; Equipment Design; Eyeglasses; Female; Humans; Lactic Acid; Male; Monitoring, Physiologic; Potentiometry; Sweat; Wireless Technology
PubMed: 28470263
DOI: 10.1039/c7lc00192d -
ACS Sensors Oct 2021Potentiometric sensors induce a spontaneous voltage that indicates ion activity in real time. We present here an advanced self-powered potentiometric sensor with memory....
Potentiometric sensors induce a spontaneous voltage that indicates ion activity in real time. We present here an advanced self-powered potentiometric sensor with memory. Specifically, the approach allows for one to record a deviation from the analyte's original concentration or determine whether the analyte concentration has surpassed a threshold in a predefined time interval. The sensor achieves this by harvesting energy in a capacitor and preserving it with the help of a diode. While the analyte concentration is allowed to return to an original value following a perturbation over time, this may not influence the sensor readout. To achieve the diode function, the sensor utilizes an additional pair of driving electrodes to move the potentiometric signal to a sufficiently high base voltage that is required for operating the diode placed in series with the capacitor and between the sensing probes. A single voltage measurement across the capacitor at the end of a chosen time interval is sufficient to reveal any altered ion activity occurring during that period. We demonstrate the applicability of the sensor to identify incurred pH changes in a river water sample during an interval of 2 h. This approach is promising for achieving deployable sensors to monitor ion activity relative to a defined threshold during a time interval with minimal electronic components in a self-powered design.
Topics: Electrodes; Electronics; Potentiometry
PubMed: 34582164
DOI: 10.1021/acssensors.1c01273 -
Inorganic Chemistry Jun 2022As an element-equivalent theranostic pair, lead-203 (Pb, 100% EC, half-life = 51.92 h) and lead-212 (Pb, 100% β, half-life = 10.64 h), through the emission of γ rays...
As an element-equivalent theranostic pair, lead-203 (Pb, 100% EC, half-life = 51.92 h) and lead-212 (Pb, 100% β, half-life = 10.64 h), through the emission of γ rays and an α particle in its decay chain, respectively, can aid in the development of personalized targeted radionuclide treatment for advanced and currently untreatable cancers. With these isotopes currently being used in clinical trials, an understanding of the relationship between the chelator structure, ability to incorporate the radiometal, and metal-complex stability is needed to help design appropriate chelators for clinical use. Herein, we report an investigation into the effect of ring size in macrocyclic chelators where pyridine, an intermediate Lewis base, acts as an electron donor toward lead. Crown-4Py (4,7,13,16-tetrakis(pyridin-2-ylmethyl)-1,10-dioxa-4,7,13,16-tetraazacyclooctadecane), cyclen-4Py (1,4,7,10-tetrakis(pyridin-2-ylmethyl)-1,4,7,10-tetraazacyclododecane), and NOON-2Py (7,16-bis(pyridin-2-ylmethyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane) were synthesized and analyzed for their ability to coordinate Pb. Metal complex stability was investigated via [Pb]Pb radiolabeling studies, H NMR spectroscopy, X-ray crystallography, and potentiometry. With the smallest macrocyclic backbone, cyclen-4Py had the highest radiochemical yield, while, in descending order, crown-4Py and NOON-2Py had the lowest. Thermodynamic stability constants (log ) of 19.95(3), 13.29(5), and 11.67 for [Pb(Cyclen-4Py)], [Pb(Crown-4Py)], and [Pb(NOON-2Py)], respectively, correlated with their radiochemical yields. The X-ray crystal structure of the least stable complexes [Pb(NOON-2Py)] revealed a hemidirected Pb center, as reflected by a void within the coordination sphere, and [Pb(Crown-4Py)] showed an average Pb-N pyridine interatomic distance of >3 Å. By contrast, the crystal structure of [Pb(Cyclen-4Py)] showed shorter Pb-N pyridine interactions, and in solution, only one highly symmetric isomer existed for this complex, whereas conformational flexibility was observed for both [Pb(Crown-4Py)] and [Pb(NOON-2Py)] at the NMR timescale. This study illustrates the importance of the macrocyclic backbone size when incorporating bulky electron-donor groups into the design of a macrocyclic chelator as it affects the accessibility of lead to the donor arms. Our results show that cyclen-4Py is a promising chelator for future studies with this theranostic pair.
Topics: Chelating Agents; Coordination Complexes; Crystallography, X-Ray; Cyclams; Lead; Ligands; Pyridines
PubMed: 35704752
DOI: 10.1021/acs.inorgchem.2c01114 -
Journal of Contaminant Hydrology Oct 2015The emplacement of nano zerovalent iron (nZVI) for groundwater remediation is usually monitored by common measurements such as pH, total iron content, and... (Review)
Review
The emplacement of nano zerovalent iron (nZVI) for groundwater remediation is usually monitored by common measurements such as pH, total iron content, and oxidation-reduction potential (ORP) by potentiometry. However, the interpretation of such measurements can be misleading because of the complex interactions between the target materials (e.g., suspensions of highly reactive and variably aggregated nanoparticles) and aquifer materials (sediments and groundwater), and multiple complications related to sampling and detection methods. This paper reviews current practice for both direct and indirect characterizations of nZVI during groundwater remediation and explores prospects for improving these methods and/or refining the interpretation of these measurements. To support our recommendations, results are presented based on laboratory batch and column studies of nZVI detection using chemical, electrochemical, and geophysical methods. Chemical redox probes appear to be a promising new method for specifically detecting nZVI, based on laboratory tests. The potentiometric and voltammetric detections of iron nanoparticles, using traditional stationary disc electrodes, rotating disc electrodes, and flow-through cell disc electrodes, provide insight for interpreting ORP measurements, which are affected by solution chemistry conditions and the interactions between iron nanoparticles and the electrode surface. The geophysical methods used for characterizing ZVI during groundwater remediation are reviewed and its application for nZVI detection is assessed with results of laboratory column experiments.
Topics: Electrochemical Techniques; Environmental Monitoring; Environmental Restoration and Remediation; Groundwater; Iron; Nanoparticles; Oxidation-Reduction; Water Pollutants, Chemical
PubMed: 25841976
DOI: 10.1016/j.jconhyd.2015.03.004