A nanoparticle, which has a metal oxide core and a cerium shell is provided. The weight ratio of the cerium within the shell to the metal oxide in the core is at least 1%. Additionally a method for delivering a ligand into a cell with the nanoparticle is provided. Processes for making the nanoparticle which include: sonicating an aqueous composition containing Ceric Ammonium Nitrate and a prefabricated nanoparticle suspension； and (b) adding a polycationic polymer to the mixture (for NP surface functionalization), are also described
