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Two-Dimensional Microfluidic Bioarray for Nucleic Acid Analysis
Published in Iniewski Krzysztof, Integrated Microsystems, 2017
Implementation of parallel sample hybridizations in multiple microchannels raises the question of finding an effective way of simultaneous liquid delivery. The conventional liquid pumping method used in microfluidics is pressure-driven flow by syringe pumping or vacuum suction. Because each microchannel has to be connected to a pump tubing and synchronization has to be considered in order to ensure parallel flows, this arrangement could be complicated in case many channels are to be used in this method. Another drawback of this pumping method is that a high pressure is required for liquid delivery in long and narrow microchannels, and this in turn requires a very tight sealing between the microfluidic channel plate and the substrate. For example, a steel clamp was used to tighten a microfluidic microarray assembly [52]. Electroosmotic flow (EOF) is another microflow-driven method and it has been used for parallel pumping of multiple channels [71,72]. However, the flow control of the EOF method depends not only on the applied voltage across the microchannel, but also on the surface physicochemical properties of the microchannel as well as the ionic strength of the buffered solutions [73]. The high ionic concentration typical of DNA hybridization buffer [12,74,75] may result in excessive Joule heating and electrolysis [42,76–78]. These effects will result in dynamic changes in the liquid temperature and pH value [79], causing instability of hybridization and SNP discrimination performance. Therefore, only a few reports were published in terms of applying EOF flow to microfluidic DNA microarray analysis [42].
Iontophoresis: Applications in Drug Delivery and Noninvasive Monitoring *
Published in Richard H. Guy, Jonathan Hadgraft, Transdermal Drug Delivery, 2002
M. Begoña Delgado-Charro, Richard H. Guy
Electroosmotic flow is a nonequilibrium process that may be analyzed by nonequilibrium thermodynamics (7). Briefly, electroosmosis is an electrokinetic phenomenon, the reciprocal of a “streaming current” (43), which corresponds to the flow of charge and volume that results from the application of a pressure gradient across a permselective membrane. In an iontophoretic experiment, a voltage is applied at a constant pressure that results in flows of charge and volume.
Drug Monitoring by Capillary Electrophoresis
Published in Steven H. Y. Wong, Iraving Sunshine, Handbook of Analytical Therapeutic Drug Monitoring and Toxicology, 2017
Currently used methods for monitoring, screening, and confirmation of drugs in body fluids are based on the principles of spectrophotometry, immunoassays, and chromatography.1–3 Recently, instrumentation for electrokinetic separations in fused-silica capillaries of very small ID became available and the feasibility of employing capillary electrophoresis (CE4,5) for drug monitoring in body fluids, including plasma, serum, saliva and urine, has been tested extensively in various laboratories.6 The central part of a CE setup (Figure 1–1) is a fused-silica capillary of 25 to 75 μm ID and 15 to 100 cm length which is mounted between two vials which house the driving electrodes and the buffers. After filling the capillary with buffer and applying a small amount of sample at one column end, a high voltage DC electric field is applied along the column which not only induces electrophoretic transport and separations of charged compounds, but in case of a charged inner capillary wall also a movement of the entire liquid along the capillary (electroosmosis). Electroosmotic flow is characterized by a flat flow profile (a plug) and not a parabolic distribution associated with hydrodynamic flow within a capillary tube. Thus, in an electrokinetically pumped configuration hardly any solute dispersion based upon the flow profile is observed and sample zone broadening is mainly caused by longitudinal diffusion, electrophoretic dispersion due to conductivity changes, thermal effects, and solute sorption. Both electroosmosis and sample-wall interactions can be favorably influenced or minimized via permanent modification of the inner walls of capillaries or via dynamic coating of the walls with agents added to the buffer.4,5
Application of iontophoresis in ophthalmic practice: an innovative strategy to deliver drugs into the eye
Published in Drug Delivery, 2023
Dong Wei, Ning Pu, Si-Yu Li, Yan-Ge Wang, Ye Tao
The direct-field effect, also called the Nernst-Planck effect, is based on the principle of ion movement caused by an applied electrical potential gradient. The ionized substances are attracted by direct-field effect to anode or the cathode depend on the charge. The direct-field effect, is the largest contributor to flux enhancement for small ions, but not the only one. Electroosmosis, also called the Electroosmotic flow, is the bulk fluid flow which occurs when a voltage difference is imposed across a charge membrane (Eljarrat-Binstock & Domb, 2006). The motion of the solvent can enhance the transport of ionic and neutral drugs. Electroosmosis is a dominant mechanism for the enhanced transport of large monovalent ionic during iontophoresis. Electropermeabilization is the alteration of a tissue barrier under the influence of an electric field that can increase the permeability of the tissue during and after iontophoresis (Li & Hao, 2018). The porosity of a membrane and the properties of the transport pathways in the membrane can be altered by the electric field. For neutral molecule, the electroosmotic flow is the major mechanism. Siva Ram Kiran Vaka et al found that the transport enhancement by iontophoresis was predominantly caused by the electrophoresis and/or electro-osmosis (Vaka et al., 2008).
Electroosmotically driven flow of micropolar bingham viscoplastic fluid in a wavy microchannel: application of computational biology stomach anatomy
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Anber Saleem, Mishal Nayab Kiani, Sohail Nadeem, Salman Akhtar, Mehdi Ghalambaz, Alibek Issakhov
The pumping mechanism that is used to transport the fluid inside a microfluidic device has significant importance due to its applications. The electro-osmotic flow phenomenon has advantage over magnetohydrodynamics, piezoelectrics and electrohydrodynamics due to its simple design, comparatively low cost and their relaxed fabrication (van Lintel et al. 1988; Richter et al. 1991; Arulanandam and Li 2000; Lemoff and Lee 2000). The flow is fully developed without the movement of any mechanical part. The basic peristalsis principle and electro-osmotic effects are used in working of many micro-pumps. The highly applicable areas of electro-osmosis phenomenon involve drug delivery by diagnostic medical apprautus, treatment of diseases, (i.e., sickle cell, anomaly in cells and blood related medical problems.). Some important non-Newtonian fluid models are given (Khan et al. 2018; Qayyum et al. 2018; Khan et al. 2019).
Non-invasive targeted iontophoretic delivery of cetuximab to skin
Published in Expert Opinion on Drug Delivery, 2020
Maria Lapteva, Marwa A. Sallam, Alexandre Goyon, Davy Guillarme, Jean-Luc Veuthey, Yogeshvar N. Kalia
Electrophoretic mobility of CTX was measured by capillary zone electrophoresis (CZE) performed on an HP3DCE system (Agilent, Waldbronn, Germany) equipped with a diode array detector operated at 200 nm. Bare fused silica capillaries (50 μm ID, 363 μm OD) were obtained from Polymicro Technologies (Phoenix, AZ, USA). The capillary total and effective lengths were 32.5 cm and 24 cm, respectively, and the temperature of the capillary cassette was maintained at 25°C. The CZE method was adapted from that described by Goyon et al. [26] for the analysis of FDA-approved basic mAbs (pI > 8). To limit protein adsorption on the bare silica wall, a dynamic coating of the capillary was carried out by the use of a background electrolyte (BGE) containing 1% PEO (average MW of 100 000 Da). The BGE was buffered using 100 mM Bis-Tris and pH adjusted to 4.0, 5.5, or 7.0 with acetic acid. New capillaries were flushed with 0.1 M hydrochloric acid for 20 min at 1 bar and the BGE for 40 min at 1 bar. Similar sequence was performed prior to each injection with 0.1 M hydrochloric acid (5 min) and the BGE (10 min). The CTX sample was diluted to 1 mg/mL with water and injected at 30 mBar for 10 s. A solution of 5% acetone in water (v/v) was also injected to check the presence of the capillary electroosmotic flow (EOF). The separation voltage was set at +15 kV (currents of ~ 46, 43 and 11 μA at a BGE pH of 4.0, 5.5, and 7.0, respectively).