We report the synthesis of Fe3O4/silica core/shell nanoparticles and their functionalization with S-nitrosothiols. These nanoparticles are of immense interest because of their nitric oxide (NO) release capabilities in human alveolar epithelial cells. Moreover, they act as large storage reservoirs of NO that can be targeted magnetically to the specific site with a sustainable release of NO for up to SO h. Such nanoparticles provide an enhancement of the biocompatibility with released NO while allowing intracellular accumulation ascribed to their small size.