(357b) On the Design of Stents for Implant Assisted Magnetic Drug Targeting

Ritter and co-workers [1-7] have been studying the possibility of using ferromagnetic stents to enhance magnetic drug targeting (MDT). In MDT, an external magnetic field is used to attract and retain magnetic drug carrier particles (MDCPs) at a specific site in the body. The additional use of ferromagnetic implants under an external field helps significantly to improve the collection of the MDCPs by more easily overcoming local convective forces and allowing collection farther from the source of the external magnetic field. However, the only stents that have been considered for use in an implant assisted (IA) MDT system have been those used in typical angioplasty procedures. But, this might not be the best design for MDT applications.

One of the main problems with the design of medical stents is that they are meant for vascular expansion not for collection. In the current form, the stent wires are against the wall and significantly away from the main flow of blood in the vessel, which could limit the ability of the stent to collect MDCPs that are not too close to the vessel wall. In addition the scaffold of stents for this particular approach may not be necessarily fully magnetic. The existence of non-ferromagnetic elements within the stent scaffold may help create stagnation zones that help improve collection at the ferromagnetic elements of the stent. This presentation will discuss the application of novel stent designs that are better suited for MDT applications.

In particular, these new stent designs will take advantage of having wires not just against the wall, but also more toward the center of the vessel to improve collection. Non-magnetic wires will also be used to create stagnation zones to slow the flow to also improve collection. This study will reveal the role of several design parameters on the performance of these new stent designs for IA-MDT including the relative location between the wires and the distance of the wires to the vessel wall, the fluid velocity and the strength of the applied magnetic field.

1. J. A. Ritter, A. D. Ebner, K. D. Daniel, and K. L. Stewart, ?Application of High Gradient Magnetic Separation Principles to Magnetic Drug Targeting,? J. Magnetism and Magnetic Materials, 280, 184-201 (2004).

2. J. A. Ritter, A. D. Ebner, K. D. Daniel, and K. L. Stewart, ?Application of High Gradient Magnetic Separation Principles to Magnetic Drug Targeting,? J. Magnetism and Magnetic Materials, 280, 184-201 (2004).

3. M. O. Aviles, A. D. Ebner, H. Chen, A. J. Rosengart, M. D. Kaminski, and J. A. Ritter, ?Theoretical Analysis of a Transdermal Ferromagnetic Implant for Retention of Magnetic Drug Carrier Particles,? J. Magnetism and Magnetic Materials, 293, 605-615 (2005).

4. A. J. Rosengart, M. D. Kaminski, H. Chen, P. L. Caviness, A. D. Ebner and J. A. Ritter, ?Magnetizable Intraluminal Stent and Functionalized Magnetic Carriers: A Novel Approach for Non-Invasive Yet Targeted Drug Delivery,? J. Magnetism and Magnetic Materials, 293, 633-638 (2005).

5. H. Chen, A. D. Ebner, A. J. Rosengart, M. D. Kaminski, and J. A. Ritter, ?Analysis of Magnetic Drug Carrier Particle Capture by a Magnetizable Intravascular Stent. Part 2: Parametric Study with Multi-Wire Two-Dimensional Model,? J. Magnetism and Magnetic Materials, 293, 616-632 (2005).

6. M. O. Avilés, A. D. Ebner and J. A. Ritter, ?Ferromagnetic Seeding for the Magnetic Targeting of Drugs and Radiation in Capillary Beds,? J. Magnetism and Magnetic Materials, 310, 131-144 (2007).

7. M. O. Avilés, A. D. Ebner and J. A. Ritter, ?Ferromagnetic Seeding for the Magnetic Targeting of Drugs and Radiation in Capillary Beds,? J. Magnetism and Magnetic Materials, 310, 131-144 (2007).