Assembly of multicellular constructs and microarrays of cells using magnetic nanowires

Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland, United States
Lab on a Chip (Impact Factor: 6.12). 07/2005; 5(6):598-605. DOI: 10.1039/b500243e
Source: PubMed


An approach is described for controlling the spatial organization of mammalian cells using ferromagnetic nanowires in conjunction with patterned micromagnet arrays. The nanowires are fabricated by electrodeposition in nanoporous templates, which allows for precise control of their size and magnetic properties. The high aspect ratio and large remanent magnetization of the nanowires enable suspensions of cells bound to Ni nanowires to be controlled with low magnetic fields. This was used to produce one- and two-dimensional field-tuned patterning of suspended 3T3 mouse fibroblasts. Self-assembled one-dimensional chains of cells were obtained through manipulation of the wires' dipolar interactions. Ordered patterns of individual cells in two dimensions were formed through trapping onto magnetic microarrays of ellipsoidal permalloy micromagnets. Cell chains were formed on the arrays by varying the spacing between the micromagnets or the strength of fluid flow over the arrays. The positioning of cells on the array was further controlled by varying the direction of an external magnetic field. These results demonstrate the possibility of using magnetic nanowires to organize cells.

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    • "The main focus of latter works is to manipulate cells using dielectrophoresis through a CMOS chip that generates an electric field (EF) with low voltages. Indeed, using dielectrophoresis leads to an easier system integration as it can be controlled by a dedicated integrated circuit which implies an easier microsystem set-up unlike other techniques such as magnethephoretic manipulation that have more constraints [10], [11] or other optical manipulations [12]. Table I presents a comparison between the main cell manipulation techniques. "
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    ABSTRACT: We present in this paper a new Lab-on-Chip (LoC) architecture for dielectrophoresis-based cell manipulation, detection, and capacitive measurement. The proposed LoC is built around a CMOS full-custom chip and a microfluidic structure. The CMOS chip is used to deliver all parameters required to control the dielectrophoresis (DEP) features such as frequency, phase, and amplitude of signals spread on in-channel electrodes of the LoC. It is integrated to the LoC and experimental results are related to micro and nano particles manipulation and detection in a microfluidic platform. The proposed microsystem includes an on-chip 27-bit frequency divider, a digital phase controller with a 3.6(°) phase shift resolution and a 2.5 V dynamic range. The sensing module is composed of a 3 × 3 capacitive sensor array with 10 fF per mV sensitivity, and a dynamic range of 1.5 V. The obtained results show an efficient nano and micro-particles (PC05N, PA04N and PS03N) separation based on frequency segregation with low voltages less than 1.7 V and a fully integrated and reconfigurable system.
    Full-text · Article · Aug 2013 · IEEE Transactions on Biomedical Circuits and Systems
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    • "Further, the standard practices of magnetic cell manipulation [2], [3], collection [4], [5], positioning [6] and sorting [7] have been reported in various publications, typically making use of combining micro-or nano-sized superparamagnetic beads and patterned magnetic thin films array. Magnetic cell manipulation with several approaches and methodologies have been demonstrated by several groups in the past including Reich et al. [8] and Whitesides et al. [9]. Our method is to use the magneitc force originating from localized stray fields, which is induced by magnetic thin films, to actively trap the magnetically labeled cells in an ordered position. "
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    ABSTRACT: In this report, magnetic cell patterning is demonstrated through controlling the micromagnetic states in microstructured concentric rectangular ferromagnetic thin films. The number of magnetic nanoparticles entered the cells via endocytosis can be determined by magnetophoresis experiment. In concentric rectangular magnetic films, the effects of cell patterning differ from magnetic films at as-deposited state and at remnant states after applying field. Remnant states of concentric rectangular are proposed for cell patterning. Living cells can be arranged at specific diagonal direction in sequence by selectively changing the magnetic field directions.
    Full-text · Article · Jul 2013 · IEEE Transactions on Magnetics
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    • "Labelled cells can also be targeted and manipulated by external magnetic fields. In magnetic cell patterning, cells were precisely positioned by magnets [2] and this technology was employed to create microarrays of cells [3] and three dimensional multicellular structures for tissue engineering applications [4]. Magnetic cell labelling could also benefit cell-based therapies by directing stem cells to diseased sites [5] or cell-based carriers of therapeutic genes to tumours [6]. "
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    ABSTRACT: A previously developed cell labelling methodology has been evaluated to assess its potential to precisely control the degree of magnetic labelling. The two-step method provides a quick way of labelling cells by first biotinylating the cell membrane proteins and then binding streptavidin paramagnetic particles onto the biotinylated proteins. Characterisation studies on biotinylated HeLa cells have revealed that the biotin concentration on the cell surface can be varied by changing the biotinylating reagent concentration. At the optimal concentration (750 microm), a substantial surface biotin density (approximately 10(8) biotin per cell) could be achieved within 30 min. The degree of magnetic labelling could be altered by adjusting the concentration of paramagnetic particles added to the cells and the binding of the particles onto the cell surface was not considerably affected by the biotin density on the cell surface. The magnetic moment of the labelled cells was measured and correlated well with the degree of magnetic labelling. Cell viability studies indicated that the magnetic labelling was not cytotoxic. Magnetically labelled cells were then successfully targeted and manipulated by magnetic fields to form three dimensional multicellular structures.
    Full-text · Article · Sep 2009 · Biomaterials
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