Magnetic particle characterization—magnetophoretic mobility and particle size

Abstract

Quantitative characterization of magnetic particles is useful for analysis and separation of labeled cells and magnetic particles. A particle velocimeter is used to directly measure the magnetophoretic mobility, size, and other parameters of magnetic particle suspensions. The instrument provides quantitative video analysis of particles and their motion. The trajectories of magnetic particles in an isodynamic magnetic field are recorded using a high-definition camera/microscope system for image collection. Image analysis software then converts the image data to the parameters of interest. The distribution of magnetophoretic mobility is determined by combining fast image analysis with velocimetry measurements. Particle size distributions have been characterized to provide a better understanding of sample quality. The results have been used in the development and operation of analyzer protocols for counting particle concentrations accurately and measuring magnetic susceptibility and size for simultaneous display for routine application to particle suspensions and magnetically labeled biological cells. V C 2016 International Society for Advancement of Cytometry

Measurement of the magnetophoretic velocity of different superparamagnetic beads

“…With an increase in bead size, also their velocities increase. This behaviour is consistent with previously reported results for other magnetic beads like for magnetic glass microspheres with diameters in the range of 2-11 µm [21] or for other beads (1-5 µm) [22].…”

“…In [20] a microscope consisting of two poles which is generated by two pairs of permanent magnets has been used to measure the magnetophoretic mobility of different cells bound to one type of a paramagnetic carrier. Other works analysed magnetic glass microspheres with diameters in the range of 2-11 µm [21] and magnetic beads (1-5 µm) [22].…”

Application of magnetic carriers to two examples of quantitative cell analysis

“…For every recorded event at least 20 parameters are calculated and stored including velocity, magnetophoretic mobility, size, shape and image processing parameters. Additional details are given in [18], and a view of the Hyperflux TM velocimeter is given in Figure 1. An example of a data display screen is shown in Figure 2.…”

Multiplex Detection of Different Magnetic Beads Using Frequency Scanning in Magnetic Frequency Mixing Technique

“…In contrast to many of the above mentioned works from other groups, the magnetic beads used in this study are much bigger commercially available magnetic beads. This can be favourable, as it has been shown in several studies [26,27,28] that with increasing size, the beads typically move faster when they are subjected to a magnetic gradient field. This behaviour enables prior sample enrichment by magnetic separation, leading to higher concentrations inside a smaller volume and therefore easier detection.…”