Surface engineering of nanoparticles for therapeutic applications

Nanoparticles with a diameter of <100 nm are regarded as potential medical materials, as this size allows nanoparticles to circulate in vivo and possibly reach targeted tumors. Inorganic nanoparticles in particular are able to interact with light and/or magnetic fields, thus extending their potential applications to such fields as fluorescence labeling, magnetic resonance imaging and stimulus-responsive drug delivery that are essential to the diagnosis and treatment of disease. To facilitate their use in such applications, the appropriate design of surface ligands on these nanoparticles is necessary. The surface ligands determine the physicochemical properties of the surface, such as hydrophilicity/hydrophobicity and zeta potential as well as dispersibility in solution. These properties have an especially important role in determining nanoparticle cell associations, such as cellular membrane permeability, immune responses and localization in vivo. This review focuses on recent advances in the surface engineering of nanoparticles for therapeutic applications.