Research Of Physical Targeting And Aggregation Behavior Of The Paramagnetic Nanometer-Iron Nuclide(PNINs)

Objectives:To develop a new type of material-the paramagnetic nanometer-iron nuclides (PNINs) that can be used as both a source for targeted radiotherapy, and a carrier for targeted chemotherapy; to design an in-vitro system of rotating magnetic field as the guiding magnetic field to concentrate PNINs on the target area; to study theoretically and simulate numerically the transport properties and the targeting aggregation characteristics of the PNINs under the guiding magnetic field; to explore the physical target positioning system for targeted therapies of solid tumors with PNINs drugs, which could provide theoretical basis and technical parameters for clinical tumor therapy using PNINs.Methods:(1) The iron nanoparticles are prepared by chemical carbonyl method, and the paramagnetic nanometer-iron nuclides (PNINs) are produced by irradiating the prepared iron nanoparticles with the pulsed-neutron reactor. (2)The intensities and gradient distributions are compared among the circular current magnetic field, the Helmholtz coil magnetic field, the cylindrical permanent magnetic field, the circular current magnetic field and the rotating magnetic field after adding magnetic materials. Theoretical models for the physical target positioning system of the PNINs in the static magnetic field (target) and in the rotating magnetic field (in vitro) are established and simulated numerically by using ANSYS software; (3) Based on the force distribution on PNINs in the body, a theoretical model for PNINs in the target positioning system is established. Numerical simulation are carried out with MATHCAD procedure for the trajectory of PNINs carrying magnetic drugs in the rotating magnetic field; (4) The transport properties, accumulation characteristics and dynamic behavior of PNINs and drug-loaded PNIPs in the microvasculature under the guiding magnetic field are described, modelled and calculated.Results:(1) The radioactive nanometer-iron nuclides with average diameter less than 100nm are produced. The nanoparticles exhibite strong paramagnetism, radioactivity intensity and good magnetic delivery function and can be effectively positioned to the target area. (2) The magnetic field of the cylindrical permanent-magnet has the largest magnetic intensity and gradient among the three guiding magnetic fields. Addition of magnetic material into the cylindrical permanent-magnet can raise the magnetic field gradient and the aggregation of the PNINs within the target area, which is essential to targeted therapies. (3) The physical targeting system guided by the rotating magnetic field (in vitro) for the positioning of PNINs can avoid the injuries resulted from the establishment of the static magnetic field (target area). (4) The effects of the size of the magnetic drug particle, the PNINs content, the tumor depth, the blood flow rate, the vessel diameter and other factors on the drug collection rate are obtained.Conclusions:PNINs and drug-loaded particles in target positioning system, including the in-vivo constant magnetic field and the in-vitro rotating magnetic field, can gather efficiently in the target area with excellent targeting ability. The effect of targeting aggregation can be evaluated quantitatively by calculating the collection rate of PNINs drugs and the coefficient of the capture cross section.