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Green-Synthesized Nanoparticles as Potential Sensors for Health Hazardous Compounds
Published in Richard L. K. Glover, Daniel Nyanganyura, Rofhiwa Bridget Mulaudzi, Maluta Steven Mufamadi, Green Synthesis in Nanomedicine and Human Health, 2021
Rachel Fanelwa Ajayi, Sphamandla Nqunqa, Yonela Mgwili, Siphokazi Tshoko, Nokwanda Ngema, Germana Lyimo, Tessia Rakgotho, Ndzumbululo Ndou, Razia Adam
The most popular electrochemical sensors for the detection of hazardous compounds such as hydrazine and nitrobenzene are conductometric, amperometric and potentiometric sensors (Zhou et al., 2011). Amperometric sensors are leading and are more preferred in electrochemical sensing platforms, particularly when enzymes are used in the sensor construction because these techniques produce electroactive responses that can be easily detected by amperometry. In amperometry, a particular potential is applied to the working electrode against the reference electrode and the subsequent current is measured (Noah and Ndangili, 2019). Finally, in potentiometric sensing, very small currents are allowed; the potential difference between the working electrode and the reference electrode is determined without polarizing the electrochemical cell. The working electrode develops an adjustable potential depending on the action or the concentration of the analyte of interest. The change in potential is related to concentration in a logarithmic manner (Garzón et al., 2019).
Determination of oxygen status in human blood
Published in John Edward Boland, David W. M. Muller, Interventional Cardiology and Cardiac Catheterisation, 2019
The remaining component of oxygen concentration, pO2(B), is commonly measured using a Clark electrochemical cell. A platinum cathode is maintained at a negative potential relative to a silver/silver chloride reference electrode (anode), both immersed in electrolyte solution (potassium chloride). Oxygen is reduced at the platinum cathode producing a current proportional to the pO2(B). It is therefore an amperometric sensor.22 In order to recognise the analyte, most sensors for blood analytes have a receptor or recognition element that binds with the analyte, and a transduction element that converts the process into a signal which can be electrochemical or optical (optodes). Thus, the Clark electrochemical cell, by measuring the current produced by direct reduction of oxygen, has no recognition element that binds to oxygen and instead uses a recognition system.23
Experimental models and measurements to study cardiovascular physiology
Published in Neil Herring, David J. Paterson, Levick's Introduction to Cardiovascular Physiology, 2018
Neil Herring, David J. Paterson
Electrophysiological techniques can also be used to detect neurotransmitter release. In cells with large enough vesicles, their incorporation into the cell membrane during exocytosis can be detected as an increase in cell capacitance as membrane area increases. Alternatively, the release of neurotransmitters into the extracellular environment can be detected with a carbon fibre electrode ver y close to a release site, which is held at a particular potential at which the neurotransmitter may oxidize. Oxidation causes the transfer of electrons to the electrode, which can be detected as small currents via a process called amperometry. The size of the current spike can be used to estimate the number of vesicles released and the frequency of spikes gives an indication of release probability. The technique is challenging in single isolated neurons given the small amounts of vesicles being rleased at low probability; it works best with dense clusters of neurons, although it then becomes difficult to control because of the number of neurons contributing to the resultant release signal.
Point of care blood glucose devices in the hospital setting
Published in Critical Reviews in Clinical Laboratory Sciences, 2023
Nam K. Tran, Clayton LaValley, Berit Bagley, John Rodrigo
Amperometric electrochemical biosensors serve as the mainstay for glucose monitoring technology [23]. Figure 1 illustrates a typical amperometric glucose-oxidase (GO)-based biosensor. In brief, an electrical signal is produced during an enzymatically catalyzed reduction-oxidation reaction. Glucose oxidase is the most common enzyme used in BGMS biosensors. Early GO-amperometric biosensors relied on oxygen as an electron carrier as shown in Figure 1 [24]. Later GO-biosensors utilized artificial electron carriers that had the added benefit of reducing the applied electrical potential on the sensor. Utilizing GO offers the benefit of its high specificity for glucose, but this enzyme can be affected by oxygen tension, as discussed below [9,24]. As such, some manufacturers have developed amperometric sensors that use glucose dehydrogenase (GDH) coupled to electron carriers such as nicotinamide adenine dinucleotide, flavin adenine dinucleotide, or pyrroloquinoline quinone (PQQ). The drawback in using GDH is its reduced specificity for glucose [25]. Glucose sensors using coulometric, colorimetric, or spectrophotometric principles also exist but have become less common.
The electronic tongue: an advanced taste-sensing multichannel sensory tool with global selectivity for application in the pharmaceutical and food industry
Published in Pharmaceutical Development and Technology, 2023
It measures the current response to find the analyte concentration at a certain potential. Measurement involves applying a voltage between two electrodes. To prevent harming the electrode, a working potential is only applied briefly. Only when the potential is being applied is the current measured (Yin et al. 2021). During amperometric detection, an electrode experiences an electrochemical conversion (potentiostatically), and the current produced by this electrochemical reaction is then measured as shown in Figure 3(D). Only partial electrolysis occurs when using the amperometric method. The target chemical must be electroactive for this form of detection to work (at the applied potential, in the solution used, and at the prevailing pH). Due to the fact that only electroactive species may be detected, this has both a limitation and a benefit in that detection can be highly selective (Braz et al. 2022).
Nucleic acid-based electrochemical biosensors for rapid clinical diagnosis: advances, challenges, and opportunities
Published in Critical Reviews in Clinical Laboratory Sciences, 2022
Abu Hashem, M. A. Motalib Hossain, Ab Rahman Marlinda, Mohammad Al Mamun, Suresh Sagadevan, Zohreh Shahnavaz, Khanom Simarani, Mohd Rafie Johan
The amperometric biosensor generates a current when a potential is applied between the reference and working electrodes. It is a self-reliant integrated device based on the quantification of the current generated from the oxidation or reduction of an electroactive biological component [60]. The current produced is directly related to the amount of the electroactive component or its generation or feeding rate within the adjacent biocatalytic layer [61]. This biosensor is rapid, highly sensitive, specific, and precise compared with the potentiometric biosensor; it does not need thermodynamic equilibrium and its response is proportional to the amount of the analyte. The signal-to-noise ratio can be improved by increasing the amount of electroactive measurable analyte-related species [60]. However, the redox potential of other electroactive species in the sample controls the selectivity of the amperometric devices. Thus, the current measured by the device can contain the contributions of species other than the target analyte [58].