The electrokinetic properties of latex particles: comparison of electrophoresis and dielectrophoresis

Ermolina, I.; Morgan, Hywel

doi:10.1016/j.jcis.2004.11.003

Cited by 223 publications

(276 citation statements)

References 40 publications

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“…Counterions are more mobile in the diffuse layer than in the Stern layer, and contribute separately to the overall magnitude of K s and thus to the DEP behavior of nanoparticles. [28][29][30][31] A comprehensive study of the ac and dc electrokinetic properties of latex nanoparticles, as a function of suspending medium conductivity and viscosity, has been reported by Ermolina and Morgan, 32 and a theoretical modeling of the DEP force that takes into account the influence of the electrical double layer has been presented by Zhou et al 33 Analysis of the normal and tangential ionic currents that occur around and at the surface of a particle, when its diameter approaches and becomes smaller than the width of its own electrical double layer, indicates that a capacitance effect contributes to the total polarizability of the particle, and exceeds the influence of the surface conductance K s . 34,35 Basuray and Chang 34 also showed that the DEP cross-over frequency for nanocolloids is inversely proportional to the RC time constant of the diffuse layer component of the electrical double layer.…”

Section: ͑15͒mentioning

confidence: 99%

Review Article—Dielectrophoresis: Status of the theory, technology, and applications

2010

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A review is presented of the present status of the theory, the developed technology and the current applications of dielectrophoresis ͑DEP͒. Over the past 10 years around 2000 publications have addressed these three aspects, and current trends suggest that the theory and technology have matured sufficiently for most effort to now be directed towards applying DEP to unmet needs in such areas as biosensors, cell therapeutics, drug discovery, medical diagnostics, microfluidics, nanoassembly, and particle filtration. The dipole approximation to describe the DEP force acting on a particle subjected to a nonuniform electric field has evolved to include multipole contributions, the perturbing effects arising from interactions with other cells and boundary surfaces, and the influence of electrical double-layer polarizations that must be considered for nanoparticles. Theoretical modelling of the electric field gradients generated by different electrode designs has also reached an advanced state. Advances in the technology include the development of sophisticated electrode designs, along with the introduction of new materials ͑e.g., silicone polymers, dry film resist͒ and methods for fabricating the electrodes and microfluidics of DEP devices ͑photo and electron beam lithography, laser ablation, thin film techniques, CMOS technology͒. Around three-quarters of the 300 or so scientific publications now being published each year on DEP are directed towards practical applications, and this is matched with an increasing number of patent applications. A summary of the US patents granted since January 2005 is given, along with an outline of the small number of perceived industrial applications ͑e.g., mineral separation, micropolishing, manipulation and dispensing of fluid droplets, manipulation and assembly of micro components͒. The technology has also advanced sufficiently for DEP to be used as a tool to manipulate nanoparticles ͑e.g., carbon nanotubes, nano wires, gold and metal oxide nanoparticles͒ for the fabrication of devices and sensors. Most efforts are now being directed towards biomedical applications, such as the spatial manipulation and selective separation/enrichment of target cells or bacteria, high-throughput molecular screening, biosensors, immunoassays, and the artificial engineering of three-dimensional cell constructs. DEP is able to manipulate and sort cells without the need for biochemical labels or other bioengineered tags, and without contact to any surfaces. This opens up potentially important applications of DEP as a tool to address an unmet need in stem cell research and therapy.

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Section: ͑15͒mentioning

confidence: 99%

Review Article—Dielectrophoresis: Status of the theory, technology, and applications

2010

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“…a lower protein conductivity and consequently negative Clausius-Mosotti factor. The influence of dynamic polarization phenomena on nanocolloid polarization was recently reported 42,44 and may also hold for proteins. In addition to the ionic transport in the double-layer, the electrophoretic motion of proteins may also be responsible for the here observed transition to negative DEP.…”

Section: E Influence On Protein Dep Due To Surfactantsmentioning

confidence: 88%

“…25 For nanocolloids, corrections to the classical Maxwell Wagner O'Konski approach were suggested due to the apparent size dependent crossover frequencies. 41,42 These refinements take into account charge movement in the Stern layer and the diffuse layer. 43,44 A standard model employing Poisson-Nernst-Planck equations was also suggested accounting for ionic migration, convection, diffusion, and electrophoretic migration.…”

Section: Introductionmentioning

confidence: 99%

Tuning direct current streaming dielectrophoresis of proteins

et al. 2012

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Dielectrophoresis (DEP) of biomolecules has large potential to serve as a novel selectivity parameter for bioanalytical methods such as (pre)concentration, fractionation, and separation. However, in contrast to well-characterized biological cells and (nano)particles, the mechanism of protein DEP is poorly understood, limiting bioanalytical applications for proteins. Here, we demonstrate a detailed investigation of factors influencing DEP of diagnostically relevant immunoglobulin G (IgG) molecules using insulator-based DEP (iDEP) under DC conditions. We found that the pH range in which concentration of IgG due to streaming iDEP occurs without aggregate formation matches the pH range suitable for immunoreactions. Numerical simulations of the electrokinetic factors pertaining to DEP streaming in this range further suggested that the protein charge and electroosmotic flow significantly influence iDEP streaming. These predictions are in accordance with the experimentally observed pH-dependent iDEP streaming profiles as well as the determined IgG molecular properties. Moreover, we observed a transition in the streaming behavior caused by a change from positive to negative DEP induced through micelle formation for the first time experimentally, which is in excellent qualitative agreement with numerical simulations. Our study thus relates molecular immunoglobulin properties to observed iDEP, which will be useful for the future development of protein (pre)concentration or separation methods based on DEP.

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“…1 Functionalized latex particles are frequently used as an experimental model of charged particles. [2][3][4][5][6][7][8] These particles have acid-base ionizable groups, which are responsible for the surface charge due to their dissociation and subsequent release of counterions in solution. The properties of this kind of materials are strongly influenced by the electrostatic effects that take place at the interface.…”

Section: Introductionmentioning

confidence: 99%

A semi-grand canonical Monte Carlo simulation model for ion binding to ionizable surfaces: Proton binding of carboxylated latex particles as a case study

Madurga

Rey-Castro²,

Pastor³

et al. 2011

The Journal of Chemical Physics

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In this paper, we present a computer simulation study of the ion binding process at an ionizable surface using a semi-grand canonical Monte Carlo method that models the surface as a discrete distribution of charged and neutral functional groups in equilibrium with explicit ions modelled in the context of the primitive model. The parameters of the simulation model were tuned and checked by comparison with experimental titrations of carboxylated latex particles in the presence of different ionic strengths of monovalent ions. The titration of these particles was analysed by calculating the degree of dissociation of the latex functional groups vs. pH curves at different background salt concentrations. As the charge of the titrated surface changes during the simulation, a procedure to keep the electroneutrality of the system is required. Here, two approaches are used with the choice depending on the ion selected to maintain electroneutrality: counterion or coion procedures. We compare and discuss the difference between the procedures. The simulations also provided a microscopic description of the electrostatic double layer (EDL) structure as a function of pH and ionic strength. The results allow us to quantify the effect of the size of the background salt ions and of the surface functional groups on the degree of dissociation. The non-homogeneous structure of the EDL was revealed by plotting the counterion density profiles around charged and neutral surface functional groups.

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The electrokinetic properties of latex particles: comparison of electrophoresis and dielectrophoresis

Cited by 223 publications

References 40 publications

Review Article—Dielectrophoresis: Status of the theory, technology, and applications

Review Article—Dielectrophoresis: Status of the theory, technology, and applications

Tuning direct current streaming dielectrophoresis of proteins

A semi-grand canonical Monte Carlo simulation model for ion binding to ionizable surfaces: Proton binding of carboxylated latex particles as a case study

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