Determination of the magnetic susceptibility of labeled particles by video imaging

Reddy, Susheel; Moore, Lee R.; Sun, Liping; Zborowski, Maciej; Chalmers, Jeffrey J.

doi:10.1016/0009-2509(95)00337-1

Cited by 55 publications

(40 citation statements)

References 12 publications

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“…Additional gains in purity could be achieved by implementing multiple sorting stages within a single device, as we have demonstrated with dielectrophoretic sorting devices (25). However, we believe that an important source of this cross-contamination may not originate from the device but rather from heterogeneity in the magnetic properties of the tags (26,27). Thus, the use of magnetic tags with less variability in saturation magnetization and size should further improve the separation performance.…”

Section: Discussionmentioning

confidence: 93%

Multitarget magnetic activated cell sorter

Adams¹,

Kim

Soh

2008

Proc. Natl. Acad. Sci. U.S.A.

334

297

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Magnetic selection allows high-throughput sorting of target cells based on surface markers, and it is extensively used in biotechnology for a wide range of applications from in vitro diagnostics to cell-based therapies. However, existing methods can only perform separation based on a single parameter (i.e., the presence or absence of magnetization), and therefore, the simultaneous sorting of multiple targets at high levels of purity, recovery, and throughput remains a challenge. In this work, we present an alternative system, the multitarget magnetic activated cell sorter (MT-MACS), which makes use of microfluidics technology to achieve simultaneous spatially-addressable sorting of multiple target cell types in a continuous-flow manner. We used the MT-MACS device to purify 2 types of target cells, which had been labeled via target-specific affinity reagents with 2 different magnetic tags with distinct saturation magnetization and size. The device was engineered so that the combined effects of the hydrodynamic force produced from the laminar flow and the magnetophoretic force produced from patterned ferromagnetic structures within the microchannel result in the selective purification of the differentially labeled target cells into multiple independent outlets. We demonstrate here the capability to simultaneously sort multiple magnetic tags with >90% purity and >5,000-fold enrichment and multiple bacterial cell types with >90% purity and >500-fold enrichment at a throughput of 10 9 cells per hour.cell sorting ͉ magnetophoresis ͉ microfluidics ͉ separation

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Section: Discussionmentioning

confidence: 93%

Multitarget magnetic activated cell sorter

Adams¹,

Kim

Soh

2008

Proc. Natl. Acad. Sci. U.S.A.

334

297

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“…The horizontal cell displacement induced by the magnetic field was analyzed to produce a cell velocity distribution. The velocities were divided by the magnitude of the energy density gradient to produce a histogram of the magnetophoretic mobility in units of millimeter cubed per tesla-ampere-second (mm 3 /T-A-s) (18)(19)(20). For the magnetic field used in these experiments, the magnetically induced cell velocity of 50 mm/s corresponded to its magnetophoretic mobility of 3.4 3 10 24 mm 3 /T-A-s.…”

Section: Ctv Analysismentioning

confidence: 99%

“…The extent of cell motion in the magnetic field, referred to as magnetophoretic mobility, is related to magnetic labeling intensity and is an important parameter governing flow mode sorting. Cell Tracking Velocimetry (CTV) has been developed from particle tracking velocimetry to evaluate the movement of a labeled cell population within a magnetic field (17)(18)(19)(20). This technique involves capturing images of cells moving through a medium of known viscosity and mag-netic susceptibility in a well-defined magnetic energy density gradient, which is then analyzed to produce a histogram of the magnetophoretic mobility.…”

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confidence: 99%

Cell tracking velocimetry as a tool for defining saturation binding of magnetically conjugated antibodies

et al. 2005

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Background: Continuous flow immunomagnetic separation is an attractive alternative to current batch mode immunomagnetic separation methods because it is capable of high sorting speeds at mild cell conditions, and grants the operator better control of separation process. The control of the separation is dependent on knowledge of the amount of magnetic label attached to the cell (magnetic labeling intensity), however. Determination of the magnetic labeling is accomplished by measuring cell magnetophoretic mobility using a newly developed technique of Cell Tracking Velocimetry (CTV). Methods: Flow cytometry was used to define the antibody binding characteristics of a fluorescently tagged primary antibody. Subsequently, CTV was used to measure antibody‐binding characteristics of a magnetically tagged secondary antibody. Results: The results of this study show that CTV is capable of providing valuable information concerning the cell labeling by magnetically tagged antibodies. It was demonstrated that the magnetically conjugated antibody binding curve exhibits the same exponential increase to saturation characteristics as that seen with the fluorescently tagged antibody. Further, it was shown that the intensity of the secondary magnetic labeling is directly proportional to the intensity of the primary fluorescent label. Conclusions: CTV is an accurate tool for evaluation of magnetically conjugated antibodies. The ability to determine the intensity of magnetic labeling is necessary for the development of continuous flow immunomagnetic separations based on cell magnetophoresis. © 2005 Wiley‐Liss, Inc.

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“…For micrometer sized magnetic particles such a technique exists in the form of magnetophoretic analysis. 8 However, for particles smaller than 1 m, Brownian motion interferes with the measurements causing large measurement inaccuracies and problems with optical visibility. 9 In this letter we describe a technique that breaks this 1 m barrier by exploiting precisely the Brownian motion.…”

mentioning

confidence: 99%

Confined Brownian motion of individual magnetic nanoparticles on a chip: Characterization of magnetic susceptibility

Ommering

Nieuwenhuis

IJzendoorn

et al. 2006

Applied Physics Letters

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An increasing number of biomedical applications requires detailed knowledge of the magnetic susceptibility of individual particles. With conventional techniques it is very difficult to analyze individual particles smaller than 1μm. The authors demonstrate how the susceptibility of individual nanoparticles can be determined in an efficient way by optically analyzing the confined Brownian motion of a nanoparticle trapped in a known magnetic potential well on a chip. A setup is introduced that has a controllable two-dimensional magnetic potential well, which is defined by an integrated microscopic current wire. Susceptibility measurements have been performed on 150–450nm superparamagnetic beads. They found differences in bead susceptibility of an order of magnitude and differences in volumetric susceptibility of more than a factor of 2.

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Determination of the magnetic susceptibility of labeled particles by video imaging

Cited by 55 publications

References 12 publications

Multitarget magnetic activated cell sorter

Multitarget magnetic activated cell sorter

Cell tracking velocimetry as a tool for defining saturation binding of magnetically conjugated antibodies

Confined Brownian motion of individual magnetic nanoparticles on a chip: Characterization of magnetic susceptibility

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