Combination Of Electrophoresis Research Articles

Co-WO3 composite coating on ferritic stainless steel interconnects

In order to apply Co-WO3 composite coating to SUS 430 steel interconnects for solid oxide fuel cell (SOFC) interconnects, a combination of electrophoresis and electroplating is used, followed by thermal energy exposure to ambient temperature at 800 ℃ for up to 5 weeks. The thermal growth of the oxide scale displays a tri-layer structure with a Cr2O3 layer in the inner part, a CoWO4 layer in the middle and (Co,Fe)3O4 and Co3O4 layer in the outer part. Co-WO3 coating produces an oxide layer that not only prevents Cr2O3 development and outward transport of Cr species but also enhances the electrical behavior of the surface scale.

Utilizing the Oxygen Reduction Reaction in Particle Impact Electrochemistry: A Step toward Mediator-Free Digital Electrochemical Sensors.

The current blockade particle impact method opens a route toward highly parallelized single-entity electrochemical assays. An important limitation is, however, that a redox mediator must be present in the sample, which can detrimentally interfere with molecular recognition processes. Dissolved O2 that is naturally present in aqueous solutions under ambient conditions can in principle serve as a suitable mediator via the oxygen reduction reaction (ORR). Here, we demonstrate the validity of this concept by performing current blockade experiments to capture and detect individual microparticles at Pt microelectrodes using solely the ORR. The readout modality is independent of the absolute O2 concentration, allowing operation under varying conditions. We further determine how the trajectories of individual microparticles are influenced by the combination of electrophoresis and electroosmotic flows and how these can be utilized to provide continuous detection of cationic particles in water for environmental monitoring.

Low-frequency electrokinetics in a periodic pillar array for particle separation

Deterministic Lateral Displacement (DLD) exploits periodic arrays of pillars inside microfluidic channels for high-precision sorting of micro- and nano-particles. Previously we demonstrated how DLD separation can be significantly improved by the addition of AC electrokinetic forces, increasing the tunability of the technique and expanding the range of applications. At high frequencies of the electric field (>1 kHz) the behaviour of such systems is dominated by Dielectrophoresis (DEP), whereas at low frequencies the particle behaviour is much richer and more complex. In this article, we present a detailed numerical analysis of the mechanisms governing particle motion in a DLD micropillar array in the presence of a low-frequency AC electric field. We show how a combination of Electrophoresis (EP) and Concentration-Polarisation Electroosmosis (CPEO) driven wall-particle repulsion account for the observed experimental behaviour of particles, and demonstrate how this complete model can predict conditions that lead to electrically induced deviation of particles much smaller than the critical size of the DLD array.

Upgrading and Prophylactic Effect of Exercise in Shoulder Periarthritis

There is a consensus about the benefit of exercise in shoulder periarthritis. However, there is uncertainty about the optimal combination of physical factors, the upgrading effect of exercise over physiotherapy and about the exercise parameters, such as frequency, intensity and duration. The aim of this study is to assess the upgrading effect of exercise. A two-week effect between two combinations of physical factors without exercise was compared versus the same double combinations of physical factors with exercise. To estimate the better combination between these two double physical factors, their two-week effect was compared. To evaluate the prophylactic effect of the frequency, the intensity and the duration of the home-prescribed exercise, these parameters were analysed after six months in all patients. Forty-eight outpatients (age 56.2±15.69 years) with shoulder periarthritis (pain initiation 3.39±3.15 months before recruitment) were treated for two weeks and followed up six months later. They were divided into four treatment groups of 12 patients. The first group was treated with magnetic field and electrophoresis with lidocaine. The second group received the same combination and exercise. The third group was treated with interferential current and laser. The fourth group received the same combination and exercise. The pain was recorded before and after the daily procedures by visual-analogue scale. Before and after the two-week treatment course, shoulder range of motion and manual muscle testing were performed. After the treatment course, each patient was instructed to perform home-exercises. After six months follow-up the frequency, the intensity and the duration of the pain were recorded, as well as the frequency, the intensity and the duration of the home-exercises. ANOVA, correlation and regression analysis were applied in the statistical analysis. After the treatment course in all patients there was significant improvement regarding pain (P < 0.05), muscle strength (P < 0.05) and shoulder mobility (P < 0.05). The most significant results were recorded in the combination of interferential current, laser and exercises (P < 0.05); followed by the combination of interferential current and laser (P < 0.05); followed by the combination of electrophoresis, magneto-therapy and exercises (P < 0.05); and finally by the combination of electrophoresis and magneto-therapy (P < 0.05). There was an upgrading effect of exercise over physiotherapy (P > 0.05). There was a correlation between pain frequency and home-exercise frequency (P < 0.05). The pain frequency tended to zero at more than five times daily home-exercises (P < 0.05). Over the two-week therapeutic course the lowest pain and the highest mobility and strength showed the combination of interferential current, laser and exercises; followed by the combination of interferential current and laser; followed by the combination of electrophoresis, magneto-therapy and exercises; and finally the combination of electrophoresis and magneto-therapy. There was an upgrading effect of exercise over physiotherapy. Only the frequency of the exercise had a prophylactic effect. The incidence of pain tended to zero at exercise frequency over five times daily.

Spatial conformation measurement of gold nanorods translocated through a solid-state nanopore

The solid-state nanopore has been developed as a powerful biosensor to detect individual molecules and nanoparticles. The operational principle of the technique was to determine the volume, concentration, and zeta potential of the particles from the electrical signals as nanoparticles passing through the pore. Here, gold nanorod samples were used to measure the dynamic translocation process though a nano channel. Gold nanorods have a high throughput in silicon nitride nanopore sensing because of their positive charge characteristics. Meanwhile, a set of varied shapes of nanorods was modeled in nanopore transport. Rod-like nanoparticles were found to adjust partial conformation to enter and pass the pore, and it was found that the dynamic process of nanorod translocation is the result of a combination of electrophoresis and electroosmotic action between nanopores and nanoparticles. These results improve our understanding of the dynamics of rod-shaped biopolymers and viruses translocating through biomembranes. They provide a new way of depicting biomolecule transport in the life system.

Formation of Free-Standing Inverse Opals with Gradient Pores.

We demonstrate the fabrication of free-standing inverse opals with gradient pores via a combination of electrophoresis and electroplating techniques. Our processing scheme starts with the preparation of multilayer colloidal crystals by conducting sequential electrophoresis with polystyrene (PS) microspheres in different sizes (300, 600, and 1000 nm). The critical factors affecting the stacking of individual colloidal crystals are discussed and relevant electrophoresis parameters are identified so the larger PS microspheres are assembled successively atop of smaller ones in an orderly manner. In total, we construct multilayer colloidal crystals with vertical stacking of microspheres in 300/600, 300/1000, and 300/600/1000 nm sequences. The inverse opals with gradient pores are produced by galvanostatic plating of Ni, followed by the selective removal of colloidal template. Images from scanning electron microscopy exhibit ideal multilayer close-packed structures with well-defined boundaries among different layers. Results from porometer analysis reveal the size of bottlenecks consistent with those of interconnected pore channels from inverse opals of smallest PS microspheres. Mechanical properties determined by nanoindentation tests indicate significant improvements for multilayer inverse opals as compared to those of conventional single-layer inverse opals.

Demonstration of beta-tropomyosin (Tpm2) and duplication of the alpha-slow tropomyosin gene (TPM3) in Atlantic salmon Salmo salar.

Beta tropomyosin (Tpm2) is demonstrated for the first time at the protein level in a fish species, using a combination of electrophoresis, mass spectrometric peptide mapping and end-group analysis. Tpm2 accounts for 50% of the total tropomyosin in slow trunk muscle of the adult Atlantic salmon as determined by quantitative carboxypeptidase digestion and is also present in the head and pectoral fin. It is absent in the fast skeletal (lighter-toned) trunk muscle, the most abundant muscle, which is composed solely of an alpha-fast (Tpm1) isoform. In contrast to the mammalian homologues, salmon Tpm2 migrates faster than salmon Tpm1 in the presence of anionic detergent. Other distinguishing characteristics are a reduced content of cysteine (one per chain) and tyrosine (five per chain) and a unique carboxyl-terminal region (residues 276-284). Two isoforms (paralogs) of alpha-slow tropomyosin (Tpm3) having different contents of methionine and histidine exist in slow trunk muscle indicating duplication of the TPM3 gene. Minor skeletal muscles, surveyed for the first time, contain a mix of at least two tropomyosins - Tpm2 (~ 50% of total) in pectoral fin, jaw and tongue and another isoform, either Tpm1 (pectoral fin) or alpha-1-like Tpm (jaw and tongue). Cheek muscle contains Tpm1 and alpha 1-like Tpm in varying proportion depending upon the section (light or dark). Of the two tropomyosins in tongue, Tpm2 displays comparatively weaker affinity for troponin-Sepharose. A feature of the major sarcomeric tropomyosins in Atlantic salmon is a pair of neighbouring glycines situated between residues 20-90.

Effect of Current Density on Deposition of Ni-Mn3O4 Composite Coating and its High Temperature Behavior

The combination of electrophoresis and electrodeposition technique is an effective method to increase Mn3O4 particle content in Ni-Mn3O4 composite coatings. The effect of current density during electrodeposition process on the deposition time, surface morphology, and Mn3O4 content of the composite coating has been systematically studied. Results show that the coatings deposited at a current density of 25 mA cm−2 for 4.5 min of deposition time are most suitable. Steels with composite coatings deposited under the optimum condition are exposed at 800 °C in air for different times to reveal the thermal conversion process. The oxide scale on the samples deposited at 5 mA cm−2 and 15 mA cm−2 consists of an external (Ni,Mn,Fe)3O4 spinel layer, a middle NiO layer and an internal Mn-doped Cr2O3 layer after 100 h oxidation. Whereas NiO is non-continuous and embeds in (Ni,Mn,Fe)3O4/(Ni,Fe)3O4 spinel layer for the samples deposited at 25 mA cm−2. The scale area specific resistance (ASR) of the sample deposited at 25 mA cm−2 is lower than those of the samples deposited at 5 mA cm−2 and 15 mA cm−2 as well as uncoated steel.

Depositing alginate on the surface of bilayer emulsions

Depositing alginate on the surface of bilayer emulsions (with protein as the primary and polysaccharide as the secondary layer) is believed to improve its functionality, including: stability, storage-ability, retention, and release profile of encapsulated compounds. Recent literature has shown that polysaccharides with a higher charge density might displace polysaccharides with a lower charge density previously coated on the oil droplets and droplet aggregation is promoted. In order to investigate the competitive adsorption and possible displacement in the case that the two polysaccharides interact with each other, alginate is added to a bilayer emulsion, with whey protein isolate (WPI) as the primary and gum arabic as the secondary layer. Contrary to recent findings, alginate (highly charged polysaccharide) did not displace gum arabic (less charged polysaccharide) already deposited on the surface of droplets, which was unexpected. Alginate entrapped the whole bilayer emulsion in a network at pH 4, possibly via interaction between carboxylate groups of alginate and protein in gum arabic. This result is significant as it challenges previous hypotheses on competitive adsorption of biopolymers and has implications for the design of more effective delivery system of hydrophobic bioactive compounds.The data was collected, using a combination of electrophoresis, light scattering, isothermal titration calorimetry (ITC), turbidity measurement, Mid-infrared (MIR) spectra, light and confocal laser scanning microscopy (CLSM).

Combination of electrophoresis and electro-flocculation for the formation of adhering IrO2 pH sensing films

We demonstrate a simple scheme to produce dense and adhering IrO2 thin films on ITO substrates via a bipolar pulsing process combining both electrophoresis and electro-flocculation. Our fabrication steps entail the synthesis of negatively-charged IrO2 nanoparticles in size of 3.5 nm using NaClO as an oxidizer in conjunction with Na3IrCl6, citric acid, and NaOH. Subsequently, multiple bipolar potentiostatic pulses are imposed in which alternating positive and negative potentials engender the electrophoresis of IrO2 nanoparticles, followed by their immediate coalescence facilitated by proton-catalyzed electro-flocculation. The resulting IrO2 thin films reveal impressive physical properties in surface uniformity, robust structural integrity, and strong adhesion to the substrate. The as-synthesized IrO2 thin film exhibits an amorphous nature with a pH sensing slope between −73.6 and −71.5 mV/pH, characteristic of super-Nernstian behavior. In contrast, the annealed IrO2 sample demonstrates a crystalline rutile phase with a pH sensing slope between −49.5 and −54.7 mV/pH, consistent with typical Nernstian response. Our approach provides a new route for the formation of strong and adhering oxide films from their colloidal constituents.

Combination of electrophoresis, chromatography, and magnetism in a single separation technique: Part 1: a first theoretical evaluation

ABSTRACTMagnetic nanoparticles incorporated into the layer of a (polymeric) sorbent, covering the inner surface of a fused silica capillary, can produce—upon applying an electric field across the capillary length—an electromagnetic field that would affect to some extent the separation of charged analytes. A first theoretical assessment of such phenomenon is given here with a view of developing a novel hybrid separation technique based on the principles of electrophoresis, chromatography, and magnetism. Specifically, the effect of built-in magnetic nanoparticles, varying in absolute number, on the strength of axial electric field in an open-tubular column for capillary electrochromatography (CEC) column for CEC—being expressed through the associated changes in near-wall dielectric constant—was analyzed using linearized Poisson–Boltzmann equation.

Effect of graphite concentration on the friction and wear of Ni–Al2O3/graphite composite coatings by a combination of electrophoresis and electrodeposition

The purpose of this work was to investigate the sliding friction and wear of a novel Ni-based coating. Ni–Al2O3/graphite composite coatings were prepared on LY12 aluminum alloys using a three-step process that involved electrophoresis and electrodeposition. Uniform composite coatings with a high volume content of particles were prepared. The effects of the deposition process on the wear mechanism of these coatings were investigated. The microindentation hardness decreased, while the friction coefficient and wear loss of the coatings initially decreased and then slowly increased as the graphite content was increased. The optimum value of the graphite particle concentration in the electrophoresis bath was 1.5g/L. The embedded graphite particles formed a transfer film on the contact area and reduced the sliding friction coefficient of the composite coatings. The new Ni–Al2O3/graphite composite coating presented excellent lubricating properties and wear resistance largely due to the effects of graphite and Al2O3 particles.

Competitive adsorption and displacement of anionic polysaccharides (fucoidan and gum arabic) on the surface of protein-coated lipid droplets

The electrostatic deposition of polysaccharides on protein-coated lipid droplets can improve emulsion stability and performance. Emulsions often contain a mixture of different polysaccharides, which may compete for attachment to the lipid droplet surfaces. The purpose of this study was to investigate the competitive adsorption and displacement of two anionic polysaccharides with different molecular properties (fucoidan and gum arabic) to caseinate-coated lipid droplets, using a combination of electrophoresis, light scattering, and isothermal titration calorimetry methods. Fucoidan had a higher negative charge, molecular weight, and radius of gyration than gum arabic. Both fucoidan and gum arabic were capable of absorbing to the caseinate-coated lipid droplets due to electrostatic attraction, but fucoidan adsorbed at a higher pH (pH 6) than gum arabic (pH 4.5), and required a lower amount to saturate the droplet surfaces (around 0.03 wt% versus 0.04 wt% for saturating 0.5 wt% emulsion). The ζ-potential of the lipid droplets saturated with polysaccharide was considerably more negative for fucoidan (−40 mV) than for gum arabic (−22 mV). In the presence of a mixture of the two polysaccharides, fucoidan preferentially adsorbed to the droplet surfaces rather than gum arabic. Furthermore, fucoidan rapidly displaced gum arabic from gum arabic-coated lipid droplet surfaces, which promoted droplet aggregation and led to an exothermic enthalpy change. In contrast, gum arabic was unable to displace fucoidan from fucoidan-coated lipid droplets, which was attributed to the higher charge density of the fucoidan. These results have important implications for designing polysaccharide/protein-coated multilayer emulsions for specific applications.

Peptidomic Analysis via One-Step Direct Transfer Technology for Colorectal Cancer Biomarker Discovery

Colorectal cancer (CRC) is a major cause of cancer-related mortality worldwide. Early CRC diagnosis is critical, since patients diagnosed at an early stage have an increased five-year survival rate after surgical resection. Serum biomarkers for CRC detection have been described and peptidomic analysis is a promising approach because of its diagnostic potential. A total of 72 CRC patients and 63 healthy controls were investigated. We used a comprehensive peptide analysis technique, BLOTCHIP®-MS analysis, a combination of electrophoresis and mass spectrometry, for high sensitivity detection of trace amounts of serum peptides. The prediction model comprised five peptides: m/z 1616.66 (fibrinogen alpha chain), m/z 2390.26 (alpha-1-antitrypsin), m/z 2858.42 (AHSG S-cysteinylated form), m/z 3622.78 (VASP), and m/z 3949.98 (F. XIIIa). The three CRC groups, stages II to IV, II + IIIa, and IIIb + IV, were discriminated from controls. High diagnostic performance was suggested by AUC (0.924), sensitivity (83%), specificity (92%), and median probability ratio (6.80) to CRC stage II to IV. We describe a prediction model for CRC diagnosis using candidate biomarker peptides discovered by a one-step direct transfer technology (BLOTCHIP®-MS analysis). The high throughput technology has high reproducibility and is applicable for peptide quantification and differential analysis for biomarker discovery.

Influence of photo-cross-linking on emulsifying performance of the self-assemblies of poly(7-(4-vinylbenzyloxyl)-4-methylcoumarin-co-acrylic acid).

Polymeric micelles could be used as model polymeric particulate emulsifiers to elucidate the correlation between the micellar structure and their emulsifying performance. Photo-cross-linkable and pH-responsive micelles were prepared with amphiphilic random copolymers, poly(7-(4-vinylbenzyloxyl)-4-methylcoumarin-co-acrylic acid) (PVMAA), via the self-assembly in selective-solvent DMF/H2O and then used as polymeric particulate emulsifiers to stabilize toluene-in-water emulsions. Primary micelles, based on PVMAA with 12 mol % of hydrophobic composition, were chosen as model to investigate the influence of photo-cross-linking on the emulsifying performance. The larger shrinkage degree by photo-cross-linking (SDC) the micelles have, the lower emulsifying efficiency the micelles exhibit. Furthermore, the structural transitions of micelles with SDC of 0% and 95% in response to pH change were comparatively confirmed by a combination of electrophoresis, dynamic light scattering (DLS), and transmission electron microscopy (TEM). The micelles of various states, manipulated by photo-cross-linking and pH changes, were used as emulsifiers to stabilize toluene-in-water or styrene-in-water emulsions. For the un-cross-linked micelles, polymer chains gradually protrude from micelles with pH increasing, which benefits the increase in the emulsifying efficiency of micelles. However, as pH elevated over 8, the stability of emulsions significantly decreases due to the disintegration of micelles. On the contrary, micelles with SDC of 95% keep their structural integrity and become more rigid as pH increase, leading to lower emulsifying efficiency of micelles and worse stability of the emulsions. This paper provides a new insight into the principles governing the extremely high emulsifying efficiency of polymeric particulate emulsifiers and pH-dependent or pH-responsive properties of the formed emulsions.

The improvement of dispersibility of YIG precursor prepared via chemical coprecipitation

To prevent YIG (Y3Fe5O12) precursor from agglomeration in the chemical coprecipitation process, the relationship between YIG precursor’s surface electric charge and its dispersibility was studied through the combination of electrophoresis and SEM test. The thermochemical characteristics of YIG precursor with improved dispersibility were also investigated. The results showed: when the coprecipitation pH is smaller than 10.5, the YIG precursor is positively charged which is in favor of YIG precursor’s good dispersibility. The YIG precursor coprecipitated at pH of 9.5 has the least agglomeration due to its most positive surface electric charge. The effect of three typical surfactants viz., SDS (anionic surfactant), CATB (cationic surfactant) and p123 (non-ionic surfactant) on the surface electric charge of YIG precursor was studied. The CATB surfactant is found to be superior to the other two surfactants in the aspect of improving YIG precursor’s dispersibility. The YIG precursor with improved dispersibility has superior homogeneity. The crystallization of cubic YIG phase can be initiated directly from amorphous YIG precursor just below 758°C and completed above 758°C, without the formation of other intermediate phase and tetragonal YIG phase, which are often involved in the preparation of YIG or doped-YIG by applying chemical coprecipitation method.

Dual-responsive poly(styrene-alt-maleic acid)-graft-poly(N-isopropyl acrylamide) micelles as switchable emulsifiers

Self-assembled polymeric micelles can be used as efficient particulate emulsifiers. To explore the relationship between micellar structure and emulsification performance, pH- and temperature-responsive self-assembled micelles were prepared and used as emulsifiers, based on a novel grafted polymer poly(styrene-alt-maleic acid)-graft-poly(N-isopropyl acrylamide) (PSMA-g-PNIPAm). Structure of PSMA-g-PNIPAm micelles varies in response to pH and temperature changes and can be classified into four typical states, including shrunken, moderately swollen, extremely swollen, and inverted states, confirmed by a combination of electrophoresis, dynamic light scattering (DLS), transmission electron microscopy (TEM), and 1H NMR. This structural variation plays a key role in the emulsification performance of PSMA-g-PNIPAm micelles, according to the emulsifying characteristics of the four typical PSMA-g-PNIPAm micelles as well as the micellar morphologies on the surface of oil droplets as observed by SEM. Emulsions stabilised by micelles with moderately swollen structure are especially stable compared with either the shrunken micelles or the extremely swollen micelles, because the moderately swollen micelles combine the advantages of solid particulate emulsifiers and polymeric surfactants.

Bipolar electrode depletion: membraneless filtration of charged species using an electrogenerated electric field gradient

We report a method for removing ions from aqueous solutions without the use of a membrane. The approach, which we call bipolar electrode depletion (BED), is based on the formation of an asymmetric electric field profile in a microchannel containing a bipolar electrode (BPE). The asymmetric field arises from local increases in conductivity caused by faradaic reactions at the BPE. We show how the asymmetric field can be used to deplete anions from a microchannel via a combination of electrophoresis and electroosmosis. We also apply this approach to filter an anionic species from a mixture of charged and neutral species being transported through a microchannel via electroosmosis. This technique could be utilized for desalination or filtration of any species possessing a net charge (e.g. heavy-metals, bacteria, proteins, or functionalized-nanoparticles).

Electrokinetic study of kaolinite suspensions

In this article a new formula for the electrophoretic mobility of a spheroidal colloid is given. This formula and the formula presented in Chassagne and Bedeaux [C. Chassagne, D. Bedeaux, J. Colloid Interface Sci. 326 (2008) 240–253] for the dipolar coefficient of a spheroidal colloid are intertwined. The combination of electrophoresis and complex conductivity measurements (from which the dipolar coefficient can be derived) allows to assess both the zeta potential and the Stern layer conductance. We will in particular show that the values found for the zeta potential from both techniques are similar in the case of the kaolinite suspension studied. Electrophoretic mobility data are also presented and discussed for a wide range of ionic strengths, different types of salt and various pH. This data has been used in flocculation studies on the same kaolinite samples [F. Mietta, C. Chassagne, J.C. Winterwerp, J. Colloid Interface Sci., accepted for publication, doi:10.1016/j.jcis.2009.03.044].

Plasmid DNA Complexation with Phosphorylcholine Diblock Copolymers and Its Effect on Cell Transfection

We examined a series of novel cationic MPC-based (2-methacryloyloxyethyl phosphorylcholine) copolymers as vectors for gene delivery, with emphasis on the assessment of the effects of the charge ratio (administered via pH variation) on the complex (polyplex) formation and the subsequent transfection efficiency. A combination of electrophoresis, dynamic light scattering, and small angle neutron scattering was used to characterize the structure and charge distribution of the polyplexes formed between the copolymer and the luciferase plasmid DNA. Polymers with larger hydrophobic side chains had lower p K a values and tended to aggregate more strongly. For a given copolymer, electrostatic interaction was the main driving force for the formation of the nanopolyplexes. When the cationic copolymers were in excess, the majority of the polyplexes formed was neutral, and only a small faction of them carried net positive charges. Polyplexes formed under excess copolymer protected the DNA from restriction enzyme digestion. As the copolymers were weak polyelectrolytes, the pH had a distinct effect on the structure and charge distribution of the polyplexes formed. Below the p K a, the copolymers were found to bind with the plasmid DNA in the form of unimers, while above the p K a, the copolymers self-aggregated and complexed with DNA in the form of micelles. It was subsequently found that unimer/DNA polyplexes were far more effective in the transfection of HEK293 cells than micellar DNA polyplexes. The results thus revealed that different hydrophobicities of the side chains in the copolymer series led to different nanostructuring and charge characteristics, which had a consequential effect on the transfection efficiency. This study provided useful insight into the molecular processes underlying polyplex formation and demonstrated a strong link between structural and physical properties of polyplexes and cell transfection efficiency.