Magnetic Iron Oxide Particles Coated with Carboxydextran for Parenteral Administration and Liver Contrasting

Abstract

Rationale and objectives: To evaluate the physical and pharmacological profiles of SH U555A, a suspension of magnetic iron oxide particles that is designed to enhance the visualization of liver tumors and metastases.

Material and Methods: Chemical and physical methods were used to characterize the size and structure of these magnetic iron oxide particles in aqueous solution. The biodistribution and pharmacokinetics of the particles were studied in mice, rats and dogs. The imaging efficacy of the particles was demonstrated by MR imaging in rat liver tumors

Results: The SH U555A particles consist of low-molecular-weight carboxydextran-coated iron oxides predominantly of the γ-Fe₂O₃ form with a hydrodynamic diameter ranging from 57-59 nm and strong T2 relaxivity of 164 liters * mmol⁻¹ * S⁻¹ (water, 0.47 T). In rats the particles exhibited a dose-dependent half-life of between 2 and 3 days in the liver at a dose of 20 μmol Fe/kg and a shorter half-life at lower doses. No major side effects were found. In a rat tumor model the tumor-to-liver contrast was markedly improved after i.v. administration of SH U555A. At a dose of 14 μmol Fe/kg the half-maximal contrast-effect was obtained even in nonoptimized T1-weighted spin-echo images.

Conclusion: SH U555A is a superparamagnetic MR contrast agent for i.v. administration and has substantial potential for the demarcation of liver tumors.