Design of site-directed magnetic targeting system in acute spinal cord injury.

Effective repair immediately after spinal cord injury can improve the prognosis of the patient. Injection of membrane resealing nanomaterial is one of the most promising technique to repair the membrane. In order to improve the retention rate of membrane repair material at injury site, membrane resealing nanomaterial can be combined with magnetic nanoparticle and magnetic targeting system. In this paper, a special site directed magnetic targeting system, which contain a C-shaped permanent magnet and a ferromagnetic needle, was constructed. Simulation was conducted to analyze the influence of the shape of needle on the magnetic field to provide magnetic force large enough to make the magnetic particles stay at the target site. Results showed that the appearance of ferromagnetic needle raised both the strength and the gradient of magnetic field at the target site. Moreover, with similar apex angles, longer needles with larger diameters can produced lager magnetic field, but smaller needles has better focal area at the small injury site in spinal cord injury. These results provide a basis for design and fabrication of ferromagnetic needles when the targeting system is applied in future experiments.