The present invention relates to novel nanoparticles which can be advantageously used in the health sector as diagnostic and/or therapeutic agents. Nanoparticles of the invention comprise a metallic material at least partly covered withan hafnium oxide material or embedded therein. When compared to existing products these nanoparticles offer a remarkable benefit over risk ratio. Specifically these nanoparticles potentiate the efficiency of known metallic nanoparticles. Indeed they retain the metal intrinsic properties and are now in addition safely usable in a mammal in particular in a human being. The invention also relates to methods for producing said nanoparticles to compositions containing same and to uses thereof.
