Green-Synthesized Nanoparticles as Potential Sensors for Health Hazardous Compounds
Richard L. K. Glover, Daniel Nyanganyura, Rofhiwa Bridget Mulaudzi, Maluta Steven Mufamadi in Green Synthesis in Nanomedicine and Human Health, 2021
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).
Experimental models and measurements to study cardiovascular physiology
Neil Herring, David J. Paterson in Levick's Introduction to Cardiovascular Physiology, 2018
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.
Drug Monitoring by Capillary Electrophoresis
Steven H. Y. Wong, Iraving Sunshine in Handbook of Analytical Therapeutic Drug Monitoring and Toxicology, 2017
For electrokinetic separations, small amounts of samples (typically nL volumes or pmol to subfmol solute quantities) are introduced by electrokinetic or hydrodynamic techniques. Upon application of power (about 5 to 30 kV, 1 to 150 μA) samples are transported through the capillary by the combined action of electrophoresis and electroosmosis. Detection principles applied include, on-column direct and indirect absorbance, direct and indirect fluorescence, and occasionally, radiometry, as well as end-column or off-column monitoring employing conductivity, mass spectrometry (MS), or amperometry. Until recently, most of the employed instruments have been assembled in the researchers laboratories. Whereas the first commercial instrument emerged in 1988, there are currently about a dozen companies manufacturing electrokinetic capillary instrumentation.7 Many of these apparatuses are fully automated comprising an autosampler, as well as data gathering, and evaluation with a computerized data station.
Recent trends and perspectives in enzyme based biosensor development for the screening of triglycerides: a comprehensive review
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Vinita Hooda, Anjum Gahlaut, Ashish Gothwal, Vikas Hooda
In electrochemical techniques, amperometry is insightful in which current is the signal of concern linearly depending upon the concentration of the target analyte when a steady potential is applied [26]. In amperometric TG biosensors, the collective reaction of enzymes –lipase (LIP), glycerol kinase (GK) and gycerol-3-phosphate oxidase (GPO) generate H2O2 from TG, which is finally decomposed to release electrons at high voltages as shown in Figure 3. In an enzymatic reaction cascade, H2O2 produced is directly proportional to the flow of electrons, i.e. current which in turn, is directly proportional to the amount of analyte (TG) in the sample [27]. There are mainly two types of amperometric biosensors, which have been reported for determination of TG in past years: (1) Membrane based TG biosensors, (2) DO metric based TG biosensors
Adaptive, personalized closed-loop therapy for Parkinson’s disease: biochemical, neurophysiological, and wearable sensing systems
Published in Expert Review of Neurotherapeutics, 2021
Lazzaro di Biase, Gerd Tinkhauser, Eduardo Martin Moraud, Maria Letizia Caminiti, Pasquale Maria Pecoraro, Vincenzo Di Lazzaro
An alternative technique to microdialysis for biochemical sensing is electrochemical sensing (amperometry or voltammetry), this technique uses microelectrodes that are able to oxidize/reduce a molecule of interest. Electrochemical sensing can record relative changes in neurochemicals of interest, since currents generated from these reactions are correlated to the concentration of the electroactive molecules in the extracellular space [38]. Amperometry works through the measurement of current flow at a fixed constant potential. Whit this technique, the current is monitored continuously; therefore has a time resolution lower than ≤ 1 msec [38]. Fast scan cyclic voltammetry (FSCV), like all voltammetry, works similarly to amperometry through continuous measurement of current flow, but in this case, the potential is not constant but is linearly changed with respect to time. Voltammogram which is a diagram of measured current versus applied potential shows the chemical signature that allows identifying an analyte [38].
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 impedimetric biosensor, which is fabricated by immobilizing the NA probe onto the transducer surface, uses impedance as the transduction principle. Impedimetric biosensors measure the variation in charge capacitance and conductance of the electrode surface as determined by the variation in the activity of the electrons or ions generated during the conjugation of receptors and target analytes [71]. Generally, an electrochemical impedance spectroscopy (EIS) technique is used to measure the changes in impedance [72] generated due to hybridization or coupling of analytes with designed probes or aptamers. EIS is a sensitive indicator for diverse chemical and physical properties [73–75]. It may also be designed without the need for indicator molecules, that is, for label-free detection. This non-destructive technique could be used as a tool for investigating biorecognition events at the electrode surface [76]. However, it is time-consuming compared with amperometry or potentiometry, and may not be appropriate for POC applications. An example of an impedimetric biosensor is shown in Figure 5 [77].