Superparamagnetic iron oxide nanoparticles coated with mannan for macrophage targeting.

To develop the functionalized superparamagnetic iron oxide nanoparticles (SPIONs) demonstrating the capacities to be delivered in antigen presenting cells specifically and to be dispersed in physiological environment stably, the nanoparticle surface was coated with mannan that induces receptor-mediated endocytosis. Mannan is a water-soluble polysaccharide having high content of D-mannose residues to be recognized by mannose receptors on immunate macrophages. Mannan-coated SPIONs (mannan-SPIONs) were prepared by traditional coprecipitation method, followed by a thermochemical treatment and post-coating with mannan solution. Poly(vinyl alcohol)-coated SPIONs (PVA-SPIONs) were also prepared as a control. Upon characterization, mannan-SPIONs were proven to be suitable for MR imaging due to small size, excellent stability in ferrofluid, and low cytotoxicity. In addition mannan-SPIONs exhibited enhanced targeted delivery efficiency to macrophages than PVA-SPIONs in vitro and in vivo. Therefore, mannan as a coating material not only prevented the aggregation of SPIONs in physiological medium but also provided a capacity to be delivered in antigen presenting cells specifically, suggesting of the potential utility of mannan-SPIONs as a macrophage-targeting MRI contrast agent.