Antibody-free isolation of circulating tumor cells by dielectrophoretic field-flow fractionation

textThis work focuses on the integration of microfluidics and dielectrophoresis(DEP) with the principles of field flow fractionation (FFF) to create a continuous-flow isolator for rare and viable circulating tumor cells (CTCs) from peripheral blood mononuclear cells (PBMNs) drawn from cancer patients. The method exploits differences in the plasma membrane capacitances of tumor and blood cells, which correspond to differences in the membrane surface areas of these cell types. DEP-FFF was first adapted to measure cell membrane capacitance, cell density and deformability profiles of cell populations. These properties of the NCI-60 panel of cancer cell types, which represents the wide functional diversity of cancers from 9 organs and leukemia, were compared with the normal cell subpopulations of peripheral blood. In every case, the NCI-60 cells exhibited membrane capacitance characteristics that were distinct from blood and, as a result, they could be isolated from blood by DEP. The heightened cancer cell membrane capacitances correlated strongly with membrane-rich morphological characteristics at their growth sites, including cell flattening, dendritic projections, and surface wrinkling. Following harvest from culture and maintenance in suspension, cancer cells were found to shed cytoplasm and membrane area over time and the suspended cell populations developed considerable morphological diversity. The shedding changed the cancer cell DEP properties but they could still be isolated from blood cells. A similar shedding process in the peripheral blood could account for the surprisingly wide morphological diversity seen among circulating cells isolated from clinical specimens. A continuous flow DEP-FFF method was devised to exploit these findings by allowing CTCs to be isolated from the nucleated cells of 10 mL clinical blood specimens in 40 minutes, an extremely high throughput rate for a microfluidic-based method. Cultured cancer cells could be isolated at 70-80% efficiency using this approach and the isolation of CTCs from clinical specimens was demonstrated. The results showed that the continuous DEP-FFF method delivers unmodified, viable CTCs for analysis, is perhaps universally applicable to isolation of CTCs from different cancer types and is independent of surface antigens - making it suitable for cells lacking the epithelial markers used in currently accepted CTC isolation methods.Biomedical Engineerin

Magnetophoretic-based microfluidic device for DNA Concentration

Abstract Nucleic acids serve as biomarkers of disease and it is highly desirable to develop approaches to extract small number of such genomic extracts from human bodily fluids. Magnetic particles-based nucleic acid extraction is widely used for concentration of small amount of samples and is followed by DNA amplification in specific assays. However, approaches to integrate such magnetic particles based capture with micro and nanofluidic based assays are still lacking. In this report, we demonstrate a magnetophoretic-based approach for target-specific DNA extraction and concentration within a microfluidic device. This device features a large chamber for reducing flow velocity and an array of μ-magnets for enhancing magnetic flux density. With this strategy, the device is able to collect up to 95 % of the magnetic particles from the fluidic flow and to concentrate these magnetic particles in a collection region. Then an enzymatic reaction is used to detach the DNA from the magnetic particles within the microfluidic device, making the DNA available for subsequent analysis. Concentrations of over 1000-fold for 90 bp dsDNA molecules is demonstrated. This strategy can bridge the gap between detection of low concentration analytes from clinical samples and a range of micro and nanofluidic sensors and devices including nanopores, nanocantilevers, and nanowires

Dielectrophoresis has Broad Applicability to Marker-Free Isolation of Tumor Cells from Blood by Microfluidic Systems

The number of circulating tumor cells (CTCs) found in blood is known to be a prognostic marker for recurrence of primary tumors, however, most current methods for isolating CTCs rely on cell surface markers that are not universally expressed by CTCs. Dielectrophoresis (DEP) can discriminate and manipulate cancer cells in microfluidic systems and has been proposed as a molecular marker-independent approach for isolating CTCs from blood. To investigate the potential applicability of DEP to different cancer types, the dielectric and density properties of the NCI-60 panel of tumor cell types have been measured by dielectrophoretic field-flow fractionation (DEP-FFF) and compared with like properties of the subpopulations of normal peripheral blood cells. We show that all of the NCI-60 cell types, regardless of tissue of origin, exhibit dielectric properties that facilitate their isolation from blood by DEP. Cell types derived from solid tumors that grew in adherent cultures exhibited dielectric properties that were strikingly different from those of peripheral blood cell subpopulations while leukemia-derived lines that grew in non-adherent cultures exhibited dielectric properties that were closer to those of peripheral blood cell types. Our results suggest that DEP methods have wide applicability for the surface-marker independent isolation of viable CTCs from blood as well as for the concentration of leukemia cells from blood. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4774307]Cancer Prevention and Research Institute of Texas (CPRIT) RP100934Kleberg Center for Molecular MarkersEntertainment Industry Foundation SU2C-AACR-DT0209NCI CA016672Biomedical Engineerin

Antibody-Independent Isolation of Circulating Tumor Cells by Continuous-Flow Dielectrophoresis

Circulating tumor cells (CTCs) are prognostic markers for the recurrence of cancer and may carry molecular information relevant to cancer diagnosis. Dielectrophoresis (DEP) has been proposed as a molecular marker-independent approach for isolating CTCs from blood and has been shown to be broadly applicable to different types of cancers. However, existing batch-mode microfluidic DEP methods have been unable to process 10 ml clinical blood specimens rapidly enough. To achieve the required processing rates of 106 nucleated cells/min, we describe a continuous flow microfluidic processing chamber into which the peripheral blood mononuclear cell fraction of a clinical specimen is slowly injected, deionized by diffusion, and then subjected to a balance of DEP, sedimentation and hydrodynamic lift forces. These forces cause tumor cells to be transported close to the floor of the chamber, while blood cells are carried about three cell diameters above them. The tumor cells are isolated by skimming them from the bottom of the chamber while the blood cells flow to waste. The principles, design, and modeling of the continuous-flow system are presented. To illustrate operation of the technology, we demonstrate the isolation of circulating colon tumor cells from clinical specimens and verify the tumor origin of these cells by molecular analysis. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4774304]Cancer Prevention and Research Institute of Texas (CPRIT) RP100934Kleberg Center for Molecular MarkersApoCell, IncEntertainment Industry Foundation SU2C-AACR-DT0209Imaging Research Cente

Isolation of Circulating Tumor Cells by Dielectrophoresis

Dielectrophoresis (DEP) is an electrokinetic method that allows intrinsic dielectric properties of suspended cells to be exploited for discrimination and separation. It has emerged as a promising method for isolating circulation tumor cells (CTCs) from blood. DEP-isolation of CTCs is independent of cell surface markers. Furthermore, isolated CTCs are viable and can be maintained in culture, suggesting that DEP methods should be more generally applicable than antibody-based approaches. The aim of this article is to review and synthesize for both oncologists and biomedical engineers interested in CTC isolation the pertinent characteristics of DEP and CTCs. The aim is to promote an understanding of the factors involved in realizing DEP-based instruments having both sufficient discrimination and throughput to allow routine analysis of CTCs in clinical practice. The article brings together: (a) the principles of DEP; (b) the biological basis for the dielectric differences between CTCs and blood cells; (c) why such differences are expected to be present for all types of tumors; and (d) instrumentation requirements to process 10 mL blood specimens in less than 1 h to enable routine clinical analysis. The force equilibrium method of dielectrophoretic field-flow fractionation (DEP-FFF) is shown to offer higher discrimination and throughput than earlier DEP trapping methods and to be applicable to clinical studies