Implant assisted-magnetic drug targeting:: Comparison of in vitro experiments with theory

Implant assisted-magnetic drug targeting (IA-MDT) was studied both in vitro and theoretically, with extensive comparisons made between model and experiment. Magnetic drug carrier particles (MDCPs) comprised of magnetite encased in a polymer were collected magnetically using a ferromagnetic, coiled, wire stent as the implant and a NdFeB permanent magnet for the applied magnetic field. A 2-D mathematical model with no adjustable parameters was developed and compared to the 3-D experimental results. The effects of the fluid velocity, stent and MDCP properties, and magnetic field strength on the performance of the system were evaluated in terms of the capture efficiency (CE) of the MDCPs. In nearly all cases, the parametric trends predicted by the model were in good agreement with the experimental results: the CE always increased with decreasing velocity, increasing magnetic field strength, increasing MDCP size or magnetite content, or increasing wire size. The only exception was when experiments showed an increase in the CE with an increase in the number of loops in the wire, while the model showed no dependence. The discrepancies between experiment and theory were attributed to phenomena not accounted for by the model, such as 3-D to 2-D geometric and magnetic field orientation differences, and interparticle interactions between the MDCPs that lead to magnetic agglomeration and shearing force effects. Overall, this work showed the effectiveness of a stent-based IA-MDT system through both in vitro experimentation and corroborated theory, with the designs of the ferromagnetic wire and the MDCPs both being paramount to the CE. (C) 2008 Elsevier B. V. All rights reserved.