Abstract No. 690 Magnetic resonance imaging–visible and triggered-degradable nanocomposite microsphere for on-demand temporary embolic agents

Abstract

Temporary embolization of vessels plays a critical role in many angiographic procedures. However, predictability and reproducibility of vessel recanalization is limited, and in these situations permanent occlusion may be undesirable. The purpose of this study is to evaluate the feasibility of MRI visible and triggered degradable nanocomposite microspheres for a temporary embolic agent. Microspheres composed by superparamagnetic iron oxide nanocluster and alginate were fabricated with spray atomization and coagulation with CaCl2 solution. Size and morphology of the fabricated microspheres with different precursor concentrations and various distance between nozzle and spray were characterized by optical microscope and scanning electron microscope. MR T2 contrast effect of microspheres was measured with 7 T MRI. Triggered degradation of microspheres using various concentration of chelating agents (EDTA) was investigated. In vivo, hepatic arteries of New Zealand white rabbits (n = 3) were occluded by the intra-artery (IA) infused microspheres. Recanalization with a chelating agent were subsequently examined by angiography. The occlusion and recanalization of hepatic arteries were re-confirmed with a perfusion MR in Magnevist contrast-enhanced 3 T MR scans. Uniform-sized microspheres composed by 2%w/v sodium alginate and 5%w/w iron oxide were fabricated with 20 psi spray pressure. Iron oxide contributed to significant MR T2 contrast effect of the microspheres. Chelating agents (∼30 mM) rapidly dissolved the calcium crosslinked microspheres in both water and serum. In vivo angiography demonstrated fast recanalization of embolized right hepatic artery with the chelating agent. Finally, contrast-enhanced MRI showed the occlusion by microspheres and recanalization upon IA infusion of chelating agents. H&E and Prussian blue staining displayed dissolved microspheres in the tumor regions. Nanocomposite microspheres by a simple spray method demonstrated MRI visibility and fast triggered degradation in vitro and in vivo. Further studies will characterize this new on-demand temporary embolic agent.