Starch-Coated Superparamagnetic Nanoparticles as MR Contrast Agents

Abstract

Superparamagnetic iron oxide nanoparticles (SPION) with suitable bio-compatible coatings have been used in biomedicine, particularly in magnetic resonance imaging (MRI), tissue engineering, and drug delivery applications. In this study, we describe the synthesis of SPION and its use for experimental in-vivo applications in MRI. SPION with a mean size of 6 nm have been prepared under inert atmosphere, in a polymeric starch matrix, by controlled chemical coprecipitation of magnetite phase from aqueous solutions containing suitable salts of Fe 2+ and Fe 3+ . X-ray powder diffraction was used to confirm a pure magnetite phase for the SPION. The influence of oxidizing agents on the cleavage of the starch chains was investigated by changing the concentration of H 2 O 2 . An aqueous solution of H 2 O 2 /NaOH cleaves the glycosidic bonds and reduces the polymer chains to a critical average molecular weight. From the dynamic light scattering (DLS) size distribution, the bulk agglomeration size was decreased by approximately 50% of the bulk size when treated by H 2 O 2 . Freshly synthesized starch-coated SPION in buffered artificial cerebro-spinal fluid were injected into the brain parenchyma of anaesthetized rats for in-vivo monitoring. Analysis of T 2 *- weighted images and T 2 *- maps revealed formation of a concentration gradient for the SPION at the injection site, indicating SPION dispersion in the living brain parenchyma from the center of the injection site toward the periphery. The starch-coated SPION show a biocompatibility and possibility of being transported in the extracellular space as well as being internalized in nerve cells.