They are not magnetic to be able to respond to the EM field.17 They also cannot be easily excited by particle irradiation to induce nuclear reactions to be useful for localized cancer treatment.18 Other candidates such as nanoparticles of iron compounds, which can be easily excited by EM field to perform thermal therapy, and Boron-10 compounds, which have a very large neutron capture cross section to perform BNCT, all have shown some level of cytotoxicity, and are not perfectly biocompatible.