Preparation of core/shell type magnetic nanoparticles from poly(amino acid) derivatives and their application to molecular imaging

Abstract

Nanostructured materials exhibit unique and useful electronic, optical, and magnetic properties which can be applied to various fields. In particular, imaging science and technology has actively been adapting these nanomaterials as imaging agents. Semiconductor nanoparticles(quantum dots), fluorescent silica nano-particles, gold nanoparticles and magnetic nanoparticles have been applied as fluorescent probes in optical imaging, X-ray contrast agents for computated tomography (CT) and contrast enhancement agents for mag-netic resonance imaging (MRI), respectively. However, drug delivery technology and interface engineering and technology are necessary to apply nanomaterials as imaging probe in biomedical field. The research ob-jective of this thesis is fabrication of biocompatible and biodegradable magnetic nanoparticles from poly(amino acid)-based amphiphilic graft polymer and iron oxide nanoparticle as a MR imaging contrast agent. In chapter 2, A biocompatible and water-soluble poly(amino acid) derivative, with a hydrophilic backbone and side chains facilitating linkage to the surfaces of nanoparticles was used to coat hydrophobic $Fe_3O_4$ nanoparticles. Such nanoparticles, of various sizes (4-11 nm), were coated by coordinate bonding and hydrophobic interaction with a hydrophilic poly(amino acid) derivative, poly(2-hydrox-ethyl aspartamide). This is a new method for transfer of hydrophobic nanoparticles from organic solvents into water. The biocompatible poly(amino acid)-coated $Fe_3O_4$ nanoparticles were smaller than 30 nm in aqueous solutions, extremely stable, and maintained their stability even after several lyophilizations. The poly(amino acid)-coated nanoparticles showed no cytotoxicity, good saturation magnetization, and high $T_2$ relaxivity coefficients ($r_2$ values). In chapter 3, Water soluble iron oxide nanoparticles were synthesized by coating iron oxide nanoparticles with a hydrophilic, biocompatible, biodegradable poly(amino acid) derivativ...