EM behavior when the wavelength is large compared to the object size
James R. Nagel, Cynthia M. Furse, Douglas A. Christensen, Carl H. Durney in Basic Introduction to Bioelectromagnetics, 2018
Electrodes interact with the basic elements of the nervous system, the neurons that combine to create nerves, which transmit impulses throughout the body. A protective fatty coating called myelin insulates the nerve fibers, so that several fibers can run side by side in a bundle without interfering with each other. In this respect, nerves work much like transmission lines and are sometimes modeled this way electrically. The nerve cell uses a combination of electricity and electrochemistry. The synaptic terminals at the ends of the nerve hold neurotransmitter chemicals in membranous sacs. When the electrical signal reaches the end of the nerve, the neurotransmitters are released. The chemical neurotransmitters spread across the gap between the neurons, and at the next neuron stimulate the production of an electrical charge, which carries the nerve impulse forward into the next neuron. Thus, along the length of a neuron, the signal is purely electrical, and at the junctions, it is electrochemical. Electricity can be used to stimulate the neuron either along its length or at a junction. Receiving electrical signals must generally be done along the length of a neuron.
Iontophoresis: Applications in Drug Delivery and Noninvasive Monitoring *
Richard H. Guy, Jonathan Hadgraft in Transdermal Drug Delivery, 2002
The electrochemistry of an iontophoretic circuit is such that there is oxidation at the anode and reduction at the cathode. The flux of electrons through the “outside” circuit is exactly balanced by the flux of ions through the “inside” circuit (Fig. 1). Specifically, oxidation at the Ag/AgCl anode results in the loss of a Cl− from the solution, and this is balanced either by pushing a cation (Na+, Drug+) through the skin or by the arrival of an anion from beneath the skin (Cl–). Reciprocally, reduction at the cathode releases a chloride ion, an extra negative charge, which is neutralized either by the electromigration of an ion (Cl– or Drug for example) through the skin or by the arrival of cation from beneath. In other words, to deliver n monovalent ions through the skin, n electrons must be generated at the anode (oxidation) and transferred to the cathode, where the reduction consumes these n electrons (9,12). The number of electrons flowing through the external circuit is a direct reflection of the amount of ionic charge flowing through the skin. Herein resides the principle of controlled drug delivery/extraction in iontophoresis.
Nanotechnology-Derived Orthopedic Implant Sensors
Iniewski Krzysztof in Integrated Microsystems, 2017
Of course, the next question is how well do these MWCNTs sense new bone growth? As a starting point, experiments were conducted with the -- redox system. The redox system with an exhibition of heterogeneous one electron transfer (n = 1) is one of the most extensively studied redox couples in electrochemistry [28]. It has been performed on the cyclic voltammetry experiments of the Fe2+/3+ redox couple by placing MWCNT-Ti in an electrolyte solution of 10 mM K3Fe(CN)6 and 1 M KNO3. In potassium ferricyanide (K3Fe(CN)6), the reduction process is followed by the oxidation of under a sweeping voltage. In such studies, the iron (II/III) redox couple did not exhibit any observable peaks for bare Ti or anodized Ti electrodes, as shown in Figures 29.7a and b. This implies that the electrochemical reaction is slow on both these electrodes. However, highly directed electron transfer at the MWCNT-Ti sensor electrode was observed as redox peaks, shown in Figure 29.10c. At a scan rate of 100 mV/s in Figure 29.10c, a well-defined redox peak appeared with the anodic (Epa) and cathodic (Epc) potentials at 175 mV and 345 mV, respectively. Moreover, on the inner set of Figure 29.7c, the relationship is linear between the anodic and cathodic peak currents versus the square root of the scan rate, while the ratio of Ipa/Ipc is about 1, corresponding to the Randles–Sevcik equation 29.1. Because the root scan rate has this linear relation with the peak currents, the mass transport in this process must be by diffusion. Zhang et al. [29] found that the heterogeneous charge-transfer rate constant (k) of the complex with H2O as a solvent is 0.05 cm/s. Since the k value is in the range of 10−4–10−1 cm/s and ΔEp > 59/n mV (in this case n = 1 and ΔEp ~ 170 mV), this process is quasireversible.
Phase I and phase II metabolism simulation of antitumor-active 2-hydroxyacridinone with electrochemistry coupled on-line with mass spectrometry
Published in Xenobiotica, 2019
Agnieszka Potęga, Dorota Garwolińska, Anna M. Nowicka, Michał Fau, Agata Kot-Wasik, Zofia Mazerska
At first, cyclic voltammetry (CV) was used to initially investigate the electrochemistry of 2-OH-AC at a glassy carbon electrode in a range of positive potentials and to determine the optimum operating range of voltages for further EC/MS studies. In order to confirm the postulated oxidation mechanism of 2-OH-AC action and to identify the oxidation products, controlled-potential electrolysis of 2-OH-AC (0.5 mM in 0.02 M PBS buffer, pH 7.40) was performed at 0.50 V. To support the possibility of the formation of the stable adduct between 2-OH-AC intermediate and GSH, the tests were performed in the absence and the presence of GSH (5 mM in ultrapure water). The electrolysis measurements were carried out for 24 hours and the progress of the process was monitored periodically by application of voltammetric, spectroscopic, chromatographic and spectrometric methods.
Biodistribution and targeting properties of iron oxide nanoparticles for treatments of cancer and iron anemia disease
Published in Nanotoxicology, 2019
Edouard Alphandéry
To synthesize IONP, various chemical synthesis have been suggested, which involve: (i) co-precipitation by mixing ferrous and ferric salts in an aqueous medium (Martínez-Mera et al. 2007), (ii) electrochemistry where an electric current is applied between an anode and a cathode introduced in an electrolyte, the anode oxidizes metal ions of the electrolyte that are further reduced to metal by the cathode with the help of stabilizers (Khan and Petrikowski 2000; Ramimoghadam, Bagheri, and Hamid 2014), (iii) flow injection syntheses by mixing reagents under laminar flow regime in a capillary reactor (Salazar-Alvarez, Muhammed, and Zagorodni 2006), (iv) hydrothermal reactions in which mixed metal hydroxides can be autoclaved to produce nanoparticle powders (Wan et al. 2005), (v) laser pyrolysis where a laser heats a mixture of iron precursors and a flowing mixture of gas (Veintemillas-Verdaguer 1998), (vi) high temperature reaction of polyol with an iron source (Cai and Wan 2007), (vii) sol-gel methods in which precursors undergo hydroxylation and condensation to yield nanometric particles (sol), followed by condensation and polymerization to produce a three-dimensional metal oxide network (wet gel), ending by a heating process that results in a crystallized structure (Albornoz and Jacobo 2006), (viii) sonolysis or thermolysis involving the decomposition or collapse of organometallic precursors such as ferrous salts (Osuna et al. 1996), (ix) spray pyrolysis in which solutions of ferric salts and a reducing agent in organic solvent is sprayed in reactors leading to the condensation of the aerosol solute and solvent evaporation (Pecharromán 1994).
Biointerface: a nano-modulated way for biological transportation
Published in Journal of Drug Targeting, 2020
Pravin Shende, Varun S. Wakade
Electrochemistry approach and redox reagents lead to the formation of redox chemistry biointerface because of non-invasive and quantitative redox-stimuli properties. To create novel supramolecular peptide formation, an increase in selectivity of beta-cyclodextrin (β-CD) is necessary for complexation [37]. The study depicts the peptide trapping of azobenzene and cyclodextrin to synthesise the complex and attach to the irregular surface of the nanoparticle-containing tryptophan with a peptide group. The h–g complex on reacting with nanoparticle creates green-coloured fluorescent dots as the peptides are immobilised onto the surface. This approach stimulates the release of tryptophan peptides via electrochemical reduction of viologen [35]. The dynamic nature of the h–g complex separates the small molecules by redox reaction avoiding significant elements. Fluorescent microscope displays green dots indicating immobilisation of N-tryptophan-containing peptides on the surfaces as uniform peptide arrays [9]. Cell surface contains N-tryptophan for the reduction of viologens (toxic metabolites) by releasing the peptides [48]. Various processes like solid-phase peptide synthesis, thioalkylation and ligation strategies lead to immobilisation and peptide release for separation of the specific peptide from the mixture of peptides [49]. For example, immobilisation of tripeptide arginine–glycine–aspartic acid (RGD) ligands on the gold substrate produces an electrochemical cell adhesive control at biosurface of cell-membrane. Electrochemical activation causes the dissociation of the h–g complex and releases RGD ligands from the surface of the cell for controlling cell adhesion.
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