Application of high gradient magnetic separation principles to magnetic drug targeting

A hypothetical magnetic drug targeting system, utilizing high gradient magnetic separation (HGMS) principles, was studied theoretically using FEMLAB simulations. This new approach uses a ferromagnetic wire placed at a bifurcation point inside a blood vessel and an externally applied magnetic field, to magnetically guide magnetic drug carrier particles (MDCP) through the circulatory system and then to magnetically retain them at a target site. Wire collection (CE) and diversion (DE) efficiencies were defined and used to evaluate the system performance. CE and DE both increase as the strength of the applied magnetic field (0.3-2.0 T), the amount of ferromagnetic material (iron) in the MDCP (20-100%) and the size of the MDCP (1-10 mum radius) increase, and as the average inlet velocity (0.1-0.8 m s(-1)), the size of the wire (50-250 mum radius) and the ratio (4-10) of the parent vessel radius (0.25-1.25 mm radius) to wire radius decrease. The effect of the applied magnetic field direction (0degrees and 90degrees) on CE and DE was minimal. Under these plausible conditions, CEs as high as 70% were obtained, with DEs reaching only 30%; however, when the MDCPs were allowed to agglomerate (4-10 mum radius), CEs and DEs of 100% were indeed achieved. These results reveal that this new magnetic drug targeting approach for magnetically collecting MDCPs at a target site, even in arteries with very high velocities, is feasible and very promising; this new approach for magnetically guiding MDCPs through the circulatory system is also feasible but more limited. Overall, this study shows that magnetic drug targeting, based on HGMS principles, has considerable promise as an effective drug targeting tool with many potential applications. (C) 2004 Elsevier B.V. All rights reserved.