Liver-directed superparamagnetic iron oxide: quantitation of T2 relaxation effects.

A new liver-directed superparamagnetic iron oxide nanoparticle preparation, MDL, is described. MDL is derived from previously developed MD particles only by modification of the characteristics of the coating:chemical structure and charge. The biodistribution, pharmacokinetics, and intratissular localization of both 59Fe-labeled MD and MDL particles were analyzed. R2 relaxivities determined in aqueous solution are compared to measurements in liver tissue and to R2 of nanoparticles incorporated into synthetic microcapsules, which represent a simplified cell pattern. T2 relaxation effects of both preparations in liver tissue are discussed relative to physical parameters such as iron oxide core dimension, total particle size, and charge, and pharmacological properties such as biodistribution, pharmacokinetics, and extra/intracellular localization.