Magnetophoresis: I. detection of magnetically labeled cells

Abstract

A new method for the detection of magnetically labeled cells in suspension using an optical microscope is presented. The movement of individual cells in a nonuniform magnetic field (magnetophoresis) can be studied and the direction and velocity of their movement can be determined. Cell-associated magnetic particles (e.g., attached magnetic immunomicrospheres) influence these parameters. We developed a magnetophoresis chamber for measuring the movement of single cells in a high-gradient magnetic field. Paramagnetic erythrocytes were used to monitor the level of magnetic force in the chamber. Bw6 antigen-positive REH cells were used as a biological model. Magnetic microspheres coupled with anti-Bw6 antibody were used as magnetic labels. The movement of magnetically labeled REH cells was investigated versus the intensity of magnetic field. The magnetization of microspheres was experimentally determined by the Faraday balance method. Experimental and theoretical results substantiate the feasibility of detecting a single cell associated with a single magnetic microsphere. Thus, magnetophoresis provides a sensitive biometrical system for magnetically labeled entities.

Quantification of cellular properties from external fields and resulting induced velocity: Magnetic susceptibility

“…Analytical use of the cell labels range from qualitative fluorescence microscopic studies to the much more highly quantitative fluorescence activated cell scanning (FACS) systems. A second and much simpler analytical device is one which uses paramagnetic particles covalently bound to antibodies (Winto-Morbach et al, 1994, 1995. A further discussion of this device will be given below.…”

“…With this apparatus, measurements were made of polystyrene latex beads and red blood cells. Winto-Morbach et al (1994, 1995 developed a technique which they refer to as "magneto-cytometry," which is similar to the technique of Gill et al (1960) In this technique, erythrocytes (paramagnetic) or magnetically labeled human leukemia cells (REH and K562), contained within a small capillary tube, are placed in a high magnetic field gradient created by an electromagnet. By microscopically determining the number of cells disappearing from the field of view after turning on the magnet, the fraction of the magnetic cells can be determined.…”

Zero-velocity Magnetophoretic Method for the Determination of Particle Magnetic Susceptibility

“…In the present study, the PS particle in organic solvents spontaneously fell down because of the higher density of the particle (1.04 g/cm 3 ) than that of the organic solvents. The value of B(dB/dy) at the balanced position was obtained experimentally.…”

“…1 The magnetophoresis separation of various particles has been studied, which included paramagnetic particles of biological cells bound with magnetic particles, [2][3][4][5][6][7][8][9][10] as well as diamagnetic particles of nucleic acids and proteins, 11 single emulsion droplets, 12 single red blood cell, 13 a dysprosium(III) adsorbed organic droplet, 14,15 a single crystal of Prussian blue analogue, 16 polystyrene particles, 17 polymer beads, 18 bacillus atrophaeus spores, 19 and allergen-specific immunoglobulin E. 20 However, studies on magnetophoretic velocity analysis, which is sometimes called magnetophoretic velocimetry, to determine the particle magnetic susceptibility are still limited. The one-dimensional horizontal-migration magnetophoretic velocity, v, of a spherical particle in a liquid medium, when the density of the particle is not so far from that of the medium, hence the magnetic force, the magnetic buoyancy, and the viscous force on the particle are balanced, is expressed by the next equation: …”

Circulating tumor-cell detection and capture using microfluidic devices

“…the motion of particles in a viscous medium induced by a magnetic field on a particle or cell of magnetic or magnetizable material (e.g. magnetically-labeled cells)] [74]. Murthy and coworkers developed a continuous-flow, magnetophoretic, microfluidic, …”