Imaging and movement of iron-oxide-bound antibody microparticles in brain and cerebrospinal fluid

Therapy with monoclonal antibody conjugates has been proposed for patients with malignant intracranial tumors and meningeal carcinomatosis. One obstacle to successful immunotherapy has been the inability of adequate quantities of antibody to reach and bind malignant cells. The use of superparamagnetic antibody microparticles offers a potential solution to the problem of inadequate antibody delivery. In this report, studies of the imaging characteristics and magnetically-induced movement of iron oxide-bound antibody (IOAb) microparticles [BioMag] are described. 1 mg/ml IOAb was readily visualized using conventional CT scan technique, but produced image artifacts on MRI. Rapid movement of IOAb in vitro was noted to occur in response to a magnetic field gradient. This property was exploited in in vivo studies using laboratory animals. IOAb injected into the intrathecal space of sedated rats could be transported through the CSF and localized to the medial aspect of one cerebral hemisphere or the other, using an external magnet. Construction of specific microparticles may allow for improved delivery of therapeutic substances to specific sites within CSF pathways.