‘Magnetic bandages’ for targeted delivery of therapeutic agents

Abstract

We investigate planar periodically magnetized structures for use in targeting or controlling the delivery of therapeutic agents attached to small magnetic particles, and derive simple analytic expressions for the relevant magnetostatic forces. We show that improved particle trapping or confinement characteristics are possible relative to those that can be obtained with more conventional (i.e. uniformly magnetized) structures. These improvements include forces that are larger at close range (for equivalent magnetization densities) and that are both unidirectional and uniform over arbitrarily large areas parallel to the magnet surface. Expressions for the magnetostatic forces exerted on point-like magnetic particles in the vicinity of long rods (with circular and ellipsoidal cross sections) uniformly magnetized perpendicular to their axes are summarized in an appendix.

Modeling of magnetic bandages for drug targeting: Button vs. Halbach arrays

“…Such is the case when one-sided flux structures such as the Halbach array pictured in Fig. 5 are used [21]. It is evident from the information summarized in Figs.…”

“…This produces the situation in which most of the magnetic flux emanates from only one of the two planar faces of the array. In addition to concentrating the magnetic flux (and thus increasing the mean force that can be exerted on a magnetic microsphere at a given distance), the Halbach array yields considerably more uniform spatial distributions of magnetic forces than simpler magnet arrays [21]. Note that once again the maximum lateral extent of this array is such that it fits within a square 3.75 cm on a side.…”

Medical Applications of Magnetic Nanoparticles

“…79 In addition, it has been demonstrated by modelling that periodic magnetised arrays can be much more efficient at trapping and holding magnetic nanoparticles than conventional magnetic sources that produce field gradients. 80,81 An alternative approach to using the magnetic force therapeutically is to apply it to enhance a natural targeting process and this mode was demonstrated by Muthana et al 82 Attempts have been made to utilise monocytes, which naturally migrate into tumours from the bloodstream, to carry therapeutic agents to the heart of a tumour. Generally, the efficiency of targeting tumours this way has been found to be quite low but a significant increase was demonstrated in mice bearing tumours when the monocytes were loaded with magnetic nanoparticles and a magnetic force was applied close to the target site.…”

Structure factor of model bidisperse ferrofluids with relatively weak interparticle interactions

“…1. Two particle and three particle diagrams which are taken into account for calculation of the pair correlation function for arbitrary sized particles (1,2,3). Note that only the diagrams I 3c , I 3f , and I 3h provide non-equal contributions when differently sized vertices 1 and 2 are mirrored.…”