One of the key problems associated with drug administration is the difficulty to target specific areas or sites in the body, like cancerous tumors or arterial blockage. Typically in these cases, exceedingly large doses of a drug are needed to ensure that some of the drug reaches a specific site, a fact which unavoidably imposes substantial toxic side effects at non-targeted organs. One way to achieve drug targeting in the body is to incorporate magnetic particles into drug carriers and then to retain them at the site using an externally applied magnetic field. This process is referred to as magnetic drug targeting (MDT). However, the main limitation of MDT is that under a given set of conditions an externally applied magnetic field alone may not be able to retain a sufficient number of magnetic drug carrier particles (MDCPs) to justify its use. Such a limitation may not exist in implant-assisted (IA) MDT. When a ferromagnetic element (e.g., an implant) is placed in a magnetic field, it becomes magnetically energized creating a very strong but localized magnetic field that is far more capable of concentrating magnetic particles at the site of the implant compared to the magnetic field alone.

An IA-MDT system based on the use of seed nanoparticles to increase the capture of MDCPs in capillary tissue was studied in vitro. This IA-MDT system uses ferromagnetic particles as seeds (i.e., the implant) for collecting the MDCPs at a desired site. Two model systems were designed for in vitro flow experiments to mimic capillary tissue. They both utilized a cylindrical polyethylene porous polymer prepared using a compression melt molding and salt leaching method. In one case the magnetite nanoparticle seeds were embedded within the matrix during the melt molding process. In the second case, the seeds were captured magnetically prior to capturing the MDCP surrogates, by flowing them through the matrix just like the MDCPs. The second case is similar to how the seeds would be captured in vivo. In both cases 0.87 ƒÝm polydivinylbenzene particles embedded with magnetite nanoparticles were used as the MDCPs surrogates. In all cases a permanent magnet was used as the external magnetic field and the flow conditions were similar to those found in capillaries.

This presentation will disclose the effects of several variables on the performance of the proposed seed concept as an IA-MDT system in terms of the MDCP capture efficiency (CE). The fluid velocity, the distance to the magnet, the applied magnetic field, the seed nanoparticle size and concentration, and the MDCP concentration were studied. The results showed a significant increase in the capture of the MDCPs surrogates when the seeds were present. They also revealed considerable insight to the design of such an IA-MDT system.