Quantification of the heterogeneity of tumor cell populations is of interest for many diagnostic and therapeutic applications, including determining the cancerous stage of tumors. We attempted to ...differentiate human breast cancer cell lines from different pathologic stages and compare that with a normal human breast tissue cell line by characterizing the impedance properties of each cell line.
A microelectrical impedance spectroscopy system has been developed that can trap a single cell into an analysis cavity and measure the electrical impedance of the captured cell over a frequency range from 100 Hz to 3.0 MHz. Normal human breast tissue cell line MCF-10A, early-stage breast cancer cell line MCF-7, invasive human breast cancer cell line MDA-MB-231, and metastasized human breast cancer cell line MDA-MB-435 were used.
The whole-cell impedance signatures show a clear difference between each cell line in both magnitude and phase of the electrical impedance. The membrane capacitance calculated from the impedance data was 1.94 +/- 0.14, 1.86 +/- 0.11, 1.63 +/- 0.17, and 1.57 +/- 0.12 muF/cm(2) at 100 kHz for MCF-10A, MCF-7, MDA-MB-231, and MDA-MB-435, respectively. The calculated resistance for each cancer cell line at 100 kHz was 24.8 +/- 1.05, 24.8 +/- 0.93, 24.9 +/- 1.12, and 26.2 +/- 1.07 MOhm, respectively. The decrease in capacitances of the cancer cell lines compared with that of the normal cell line MCF-10A was 4.1%, 16.0%, and 19.1%, respectively, at 100 kHz.
These findings suggest that microelectrical impedance spectroscopy might find application as a method for quantifying progression of cancer cells without the need for tagging or modifying the sampled cells.
The magnetic separation of cells based on certain traits has a wide range of applications in microbiology, immunology, oncology, and hematology. Compared to bulk separation, performing ...magnetophoresis at micro scale presents advantages such as precise control of the environment, larger magnetic gradients in miniaturized dimensions, operational simplicity, system portability, high-throughput analysis, and lower costs. Since the first integration of magnetophoresis and microfluidics, many different approaches have been proposed to magnetically separate cells from suspensions at the micro scale. This review paper aims to provide an overview of the origins of microfluidic devices for magnetic cell separation and the recent technologies and applications grouped by the targeted cell types. For each application, exemplary experimental methods and results are discussed.
This paper presents the development of a microsystem for separating suspended breast cancer cells in peripheral blood and for sorting them based on their electrophysiological characteristics. A ...continuous paramagnetic capture mode (PMC) magnetophoretic microseparator was utilized for the isolation of suspended breast cancer cells in peripheral blood based on the native magnetic properties of blood cells without any tagging such as with magnetic probes. A micro-electrical impedance spectroscopy (μ-EIS) system was used as a downstream cell analysis tool to extract the pathological characteristics from the breast cancer cells. The system was fabricated on silicon and glass substrates utilizing microfabrication and stereolithography technologies. The experimental results of the PMC microseparator show that 94.8% of the breast cancer cells could be continuously separated out from a spiked blood sample with a 0.2
T external magnetic flux. The electrical impedances of human breast cancer cell lines of different pathological stages (MCF-7, MDA-MB-231, and MDA-MB-435) were measured using μ-EIS and compared to those of normal human breast tissue cell line MCF-10A.
We describe the lateral displacement of a particle passing over a planar interdigitated electrode array at an angle as a function of the particle size. The lateral displacement was also measured as a ...function of the angle between the electrode and the direction of flow. A simplified line charge model was used for numerically estimating the lateral displacement of fluorescent polystyrene (PS) beads with three different diameters. Using the lateral displacement as a function of particle size, we developed a lateral dielectrophoretic (DEP) microseparator, which enables continuous discrimination of particles by size. The microchannel was divided into three regions, each with an electrode array placed at a different angle with respect to the direction of flow. The experiment using an admixture of 3-, 5-, and 10-microm PS beads showed that the lateral DEP microseparator could continuously separate out 99.86% of the 3-microm beads, 98.82% of the 5-microm beads, and 99.69% of the 10-microm beads, simply by using a 200-kHz 12-Vp-p AC voltage to create the lateral DEP force. The lateral DEP microseparator is thus a practical device for simultaneously separating particles according to size from a heterogeneous admixture.
In vitro tissue culture models are often benchmarked by their ability to replicate in vivo function. One of the limitations of in vitro systems is the difficulty in preserving an orchestrated cell ...population, especially for generating three-dimensional tissue equivalents. For example, tissue-engineering applications involve large high-density constructs, requiring a perfusing system that is able to apply adequate oxygen and nutrients to the interior region of the tissue. This is particularly true with respect to thick tissue sections harvested for in vitro culture. We have fabricated a microneedle-based perfusion device for high-cell-density in vitro tissue culture from SU-8 photosensitive epoxy and suitable post-processing. The device was tested for its ability to improve viability in slices of harvested brain tissue. This model was chosen due to its acute sensitivity to disruptions in its nutrient supply. Improved viability was visible in the short term as assessed via live-dead discriminating fluorescent staining and confocal microscopy. This perfusion system opens up many possibilities for both neurobiological as well as other culture systems.
A micro electrical impedance spectroscopy (muEIS) system has been developed and implemented to analyze highly and poorly metastatic head and neck cancer (HNC) cell lines with single-cell resolution. ...The microsystem has arrays of 16 impedance analysis sites, each of which is capable of capturing a single cell and analyzing its whole-cell electrical impedance spectrum. This muEIS system was used to obtain the electrical impedance spectra of the poorly metastatic HNC cell line 686 LN and the highly metastatic HNC cell line 686 LN-M4e over a frequency range of 40 Hz - 10 MHz. The 686 LN cells had higher impedance phase compared to that of 686 LN-M4e cells at frequencies between 50 kHz and 2 MHz. This result demonstrates that the metastatic state of HNC cells can be distinguished using the developed muEIS system. This system is expected to serve as a powerful tool for future detection and quantification of cancer cells from various tumor stages.
A microscale thermal field-flow fractionation (μ-TFFF) system has been designed, fabricated, and characterized. Motivation for miniaturization of TFFF systems was established by examining the ...geometrical scaling of the fundamental TFFF theory. Miniaturization of conventional macroscale TFFF systems was made possible through utilization of micromachining technologies. Fabrication of the μ-TFFF system was discussed in detail. The μ-TFFF system was characterized for plate height versus flow rate, single-component polystyrene retention, and multicomponent polystyrene separations. Retention, thermal diffusion coefficients, and maximum diameter-based selectivity values were extracted from separation data and found comparable with macroscale TFFF system results. Retention values ranged from 0.33 to 0.46. Thermal diffusion coefficients were between 3.0 × 10-8 and 5.4 × 10-8 cm2/s·K. The maximum diameter-based selectivity was 1.40.
This paper presents the characterization of continuous single-stage and three-stage cascade paramagnetic capture (PMC) mode magnetophoretic microseparators for high efficiency separation of red and ...white blood cells from diluted whole blood based on their native magnetic properties. The separation mechanism for both PMC microseparators is based on a high gradient magnetic separation (HGMS) method. This approach enables separation of blood cells without the use of additives such as magnetic beads. Experimental results for the single-stage PMC microseparator show that 91.1% of red blood cells were continuously separated from the sample at a volumetric flow rate of 5 microl h-1. In addition, the three-stage cascade PMC microseparator continuously separated 93.5% of red blood cells and 97.4% of white blood cells from whole blood at a volumetric flow rate of 5 microl h-1.
This paper describes an approach for fabricating multi-layer microfluidic systems from a combination of glass and plastic materials. Methods and characterization results for the microfabrication ...technologies underlying the process flow are presented. The approach is used to fabricate and characterize multi-layer plastic/glass microfluidic systems containing electrical and mechanical functionality. Hot embossing, heat staking of plastics, injection molding, microstenciling of electrodes, and stereolithography were combined with conventional MEMS fabrication techniques to realize the multi-layer systems. The approach enabled the integration of multiple plastic/glass materials into a single monolithic system, provided a solution for the integration of electrical functionality throughout the system, provided a mechanism for the inclusion of microactuators such as micropumps/valves, and provided an interconnect technology for interfacing fluids and electrical components between the micro system and the macro world.
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