N-hexanoyl chitosan stabilized magnetic nanoparticles: Implication for cellular labeling and magnetic resonance imaging

Magnetic particles ranging from the nanometer to micrometer scale are being used in an increasing number of medical applications. The important properties of magnetic particles for medical applications are nontoxicity, biocompatibility, injectability, and high level accumulation in the target tissue or organ; the most important property among those mentioned above is nontoxicity. Magnetic nanoparticles offer attractive and versatile applications in the field of biotechnology, such as DNA and RNA separation, cell separation, drug delivery system (DDS), magnetic resonance imaging (MRI), and hyperthermia [1-6]. For these applications, magnetic iron oxides such as Fe3O4 or gamma-Fe2O3 are employed as a magnetic phase because they are stable and harmless to the living bodies. To make them bind to a biological entity, their surfaces are usually modified with an appropriate compound such as polyethyleneglycol (PEG) or streptavidin. Polymers like poly-L-lysine (PLL), poly ethylene imide (PEI) and dextran, and recently chitosan [6] has been used as a stabilizer (coating agent) for iron oxide nanoparticles so as to improve the nanoparticle's biocompatibility and injectability. However, high-level accumulation in the target tissue or organ and cytotoxicity; the most important property of the nanoparticles is remains to be intact.More or less to improve limitations stated above, several derivatives of chitosan have been proposed based on reactions with the free amino groups. Our research group already investigated the hydrophobic modification of natural chitosan by using three different acyl chlorides (hexanoyl, octanoyl and myristoyl chloride) so as to improve its aqueous solubility and subsequently used them for stabilization of metalic nanoparticles [7-9]. In this paper, we have selected the hexanoyl chloride modified chitosan stabilized iron oxide nanoparticles (Nac-6-IOPs or simply MC-IOPs) as a material of interest and demonstrated its biomedical application like cellular