Magnetically Targeted Microspheres for Intracavitary and Intraspinal Y-90 Radiotherapy
Targeted approaches to radiotherapy using long-range ß-emitting isotopes linked to biologically selective molecules such as antibodies have shown limited success, primarily due to the relatively small amounts of radioactive material that actually reach the tumor sites. Tissuecompatible magnetic microspheres, however, can incorporate very high concentrations of radioactive material and can be maneuvered within the body through the use of an external magnetic field like that generated by a clinical MRI machine. Magnetic microspheres (MMS), 10–30 gm in diameter, were prepared from poly (lactic acid) by a solvent-evaporation method, contained 30 weight% magnetite and were loaded shortly before injection with the ß-emitting radioisotope 90Y. This radiopharmaceutical was tested in vivo in two animal models. The results from the subcutaneous mouse lymphoma model are promising and show that the locally concentrated magnetic microspheres are able to eradicate more than half of the tumors. The results from an intraspinal glioblastoma model in rats, however, failed to show a significant difference between magnetically targeted radioactive microspheres and radioactive microspheres which had not been subjected to a magnetic field. Nonetheless, both groups of radioactively treated rats lived significantly longer than animals injected with non-radioactive microspheres. Higher magnetic fields and field gradients and more susceptible, smaller magnetic microspheres might be required to achieve intraspinal magnetic targeting.
KeywordsLactic Acid Magnetic Field Gradient Magnetic Microsphere NdFeB Magnet Magnetic Target
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