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Fulltext Dielectrophoretic manipulation and separation of microparticles using microarray dot electrodes

Yafouz B, Kadri NA, Ibrahim F

Sensors (Basel), 2014;14(4):6356-69.
PMID: 24705632 DOI: 10.3390/s140406356

This paper introduces a dielectrophoretic system for the manipulation and separation of microparticles. The system is composed of five layers and utilizes microarray dot electrodes. We validated our system by conducting size-dependent manipulation and separation experiments on 1, 5 and 15 μm polystyrene particles. Our findings confirm the capability of the proposed device to rapidly and efficiently manipulate and separate microparticles of various dimensions, utilizing positive and negative dielectrophoresis (DEP) effects. Larger size particles were repelled and concentrated in the center of the dot by negative DEP, while the smaller sizes were attracted and collected by the edge of the dot by positive DEP.

Matched MeSH terms: Electrophoresis/instrumentation
Fulltext Microarray dot electrodes utilizing dielectrophoresis for cell characterization

Yafouz B, Kadri NA, Ibrahim F

Sensors (Basel), 2013 Jul 12;13(7):9029-46.
PMID: 23857266 DOI: 10.3390/s130709029

During the last three decades; dielectrophoresis (DEP) has become a vital tool for cell manipulation and characterization due to its non-invasiveness. It is very useful in the trend towards point-of-care systems. Currently, most efforts are focused on using DEP in biomedical applications, such as the spatial manipulation of cells, the selective separation or enrichment of target cells, high-throughput molecular screening, biosensors and immunoassays. A significant amount of research on DEP has produced a wide range of microelectrode configurations. In this paper; we describe the microarray dot electrode, a promising electrode geometry to characterize and manipulate cells via DEP. The advantages offered by this type of microelectrode are also reviewed. The protocol for fabricating planar microelectrodes using photolithography is documented to demonstrate the fast and cost-effective fabrication process. Additionally; different state-of-the-art Lab-on-a-Chip (LOC) devices that have been proposed for DEP applications in the literature are reviewed. We also present our recently designed LOC device, which uses an improved microarray dot electrode configuration to address the challenges facing other devices. This type of LOC system has the capability to boost the implementation of DEP technology in practical settings such as clinical cell sorting, infection diagnosis, and enrichment of particle populations for drug development.

Matched MeSH terms: Electrophoresis/instrumentation*
Continuous separation of colloidal particles using dielectrophoresis

Yunus NA, Nili H, Green NG

Electrophoresis, 2013 Apr;34(7):969-78.
PMID: 23436439 DOI: 10.1002/elps.201200466

Dielectrophoresis is the movement of particles in nonuniform electric fields and has been of interest for application to manipulation and separation at and below the microscale. This technique has the advantages of being noninvasive, nondestructive, and noncontact, with the movement of particle achieved by means of electric fields generated by miniaturized electrodes and microfluidic systems. Although the majority of applications have been above the microscale, there is increasing interest in application to colloidal particles around a micron and smaller. This paper begins with a review of colloidal and nanoscale dielectrophoresis with specific attention paid to separation applications. An innovative design of integrated microelectrode array and its application to flow-through, continuous separation of colloidal particles is then presented. The details of the angled chevron microelectrode array and the test microfluidic system are then discussed. The variation in device operation with applied signal voltage is presented and discussed in terms of separation efficiency, demonstrating 99.9% separation of a mixture of colloidal latex spheres.

Matched MeSH terms: Electrophoresis/instrumentation*
Fulltext Dielectrophoresis of Amyloid-Beta Proteins as a Microfluidic Template for Alzheimer's Research

Al-Ahdal SA, Ahmad Kayani AB, Md Ali MA, Chan JY, Ali T, Adnan N, et al.

Int J Mol Sci, 2019 Jul 23;20(14).
PMID: 31340481 DOI: 10.3390/ijms20143595

We employed dielectrophoresis to a yeast cell suspension containing amyloid-beta proteins (Aβ) in a microfluidic environment. The Aβ was separated from the cells and characterized using the gradual dissolution of Aβ as a function of the applied dielectrophoretic parameters. We established the gradual dissolution of Aβ under specific dielectrophoretic parameters. Further, Aβ in the fibril form at the tip of the electrode dissolved at high frequency. This was perhaps due to the conductivity of the suspending medium changing according to the frequency, which resulted in a higher temperature at the tips of the electrodes, and consequently in the breakdown of the hydrogen bonds. However, those shaped as spheroidal monomers experienced a delay in the Aβ fibril transformation process. Yeast cells exposed to relatively low temperatures at the base of the electrode did not experience a positive or negative change in viability. The DEP microfluidic platform incorporating the integrated microtip electrode array was able to selectively manipulate the yeast cells and dissolve the Aβ to a controlled extent. We demonstrate suitable dielectrophoretic parameters to induce such manipulation, which is highly relevant for Aβ-related colloidal microfluidic research and could be applied to Alzheimer's research in the future.

Matched MeSH terms: Electrophoresis/instrumentation
Microfluidic dielectrophoretic cell manipulation towards stable cell contact assemblies

Md Ali MA, Kayani ABA, Yeo LY, Chrimes AF, Ahmad MZ, Ostrikov KK, et al.

Biomed Microdevices, 2018 11 06;20(4):95.
PMID: 30402766 DOI: 10.1007/s10544-018-0341-1

Cell contact formation, which is the process by which cells are brought into close proximity is an important biotechnological process in cell and molecular biology. Such manipulation is achieved by various means, among which dielectrophoresis (DEP) is widely used due to its simplicity. Here, we show the advantages in the judicious choice of the DEP microelectrode configuration in terms of limiting undesirable effects of dielectric heating on the cells, which could lead to their inactivation or death, as well as the possibility for cell clustering, which is particularly advantageous over the linear cell chain arrangement typically achieved to date with DEP. This study comprises of experimental work as well as mathematical modeling using COMSOL. In particular, we establish the parameters in a capillary-based microfluidic system giving rise to these optimum cell-cell contact configurations, together with the possibility for facilitating other cell manipulations such as spinning and rotation, thus providing useful protocols for application into microfluidic bioparticle manipulation systems for diagnostics, therapeutics or for furthering research in cellular bioelectricity and intercellular interactions.

Matched MeSH terms: Electrophoresis/instrumentation*
Dielectrophoretic deformation of breast cancer cells for lab on a chip applications

Chan JY, Ahmad Kayani AB, Md Ali MA, Kok CK, Ramdzan Buyong M, Hoe SLL, et al.

Electrophoresis, 2019 10;40(20):2728-2735.
PMID: 31219180 DOI: 10.1002/elps.201800442

This paper presents the development and experimental analysis of a curved microelectrode platform for the DEP deformation of breast cancer cells (MDA-MB-231). The platform is composed of arrays of curved DEP microelectrodes which are patterned onto a glass slide and samples containing MDA-MB-231 cells are pipetted onto the platform's surface. Finite element method is utilised to characterise the electric field gradient and DEP field. The performance of the system is assessed with MDA-MB-231 cells in a low conductivity 1% DMEM suspending medium. We applied sinusoidal wave AC potential at peak to peak voltages of 2, 5, and 10 Vpp at both 10 kHz and 50 MHz. We observed cell blebbing and cell shrinkage and analyzed the percentage of shrinkage of the cells. The experiments demonstrated higher percentage of cell shrinkage when cells are exposed to higher frequency and peak to peak voltage electric field.

Matched MeSH terms: Electrophoresis/instrumentation*
Fulltext Performance comparison of EasyFix G26 and HYDRASYS 2 SCAN for the detection of serum monoclonal proteins

Amin Nordin FD, Mohd Khalid MKN, Abdul Aziz SM, Mohamad Bakri NA, Ahmad Ridzuan SN, Abdul Jalil J, et al.

J Clin Lab Anal, 2020 Jun;34(6):e23254.
PMID: 32141626 DOI: 10.1002/jcla.23254

BACKGROUND: Serum protein electrophoresis (SPE) is a widely used laboratory technique to diagnose patients with multiple myeloma (MM) and other disorders related to serum protein. In patients with MM, abnormal monoclonal protein can be detected by SPE and further characterized using immunofixation electrophoresis (IFE). There are several semi-automated agarose gel-based systems available commercially for SPE and IFE. In this study, we sought to evaluate the analytical performance of fully automated EasyFix G26 (EFG26) and semi-automated HYDRASYS 2 SCAN (H2SCAN) for both SPE and IFE.
METHODS: Both instruments were operated according to manufacturer's instructions. Samples used include a commercially available normal control serum (NCS) and patients' specimens. The following were evaluated: precision and comparison studies for SPE, and reproducibility and comparison studies for IFE. Statistical analyses were performed using Microsoft Excel.
RESULTS: For SPE repeatability study, our results showed that EFG26 has higher coefficient of variation (%CV) compared with H2SCAN for both samples except for monoclonal component with %CV of 0.97% and 1.18%, respectively. Similar results were obtained for SPE reproducibility study except for alpha-1 (4.16%) and beta (3.13%) fractions for NCS, and beta fractions (5.36%) for monoclonal sample. Subsequently, reproducibility for IFE was 100% for both instruments. Values for correlation coefficients between both instruments ranged from 0.91 to 0.98 for the five classic bands.
CONCLUSION: Both instruments demonstrated good analytical performance characterized by high precision, reproducibility and correlation.

Matched MeSH terms: Blood Protein Electrophoresis/instrumentation*
Fulltext Cell patterning for liver tissue engineering via dielectrophoretic mechanisms

Yahya WN, Kadri NA, Ibrahim F

Sensors (Basel), 2014 Jul 02;14(7):11714-34.
PMID: 24991941 DOI: 10.3390/s140711714

Liver transplantation is the most common treatment for patients with end-stage liver failure. However, liver transplantation is greatly limited by a shortage of donors. Liver tissue engineering may offer an alternative by providing an implantable engineered liver. Currently, diverse types of engineering approaches for in vitro liver cell culture are available, including scaffold-based methods, microfluidic platforms, and micropatterning techniques. Active cell patterning via dielectrophoretic (DEP) force showed some advantages over other methods, including high speed, ease of handling, high precision and being label-free. This article summarizes liver function and regenerative mechanisms for better understanding in developing engineered liver. We then review recent advances in liver tissue engineering techniques and focus on DEP-based cell patterning, including microelectrode design and patterning configuration.

Matched MeSH terms: Electrophoresis/instrumentation