Methods of preparing a composition comprising non-ionic, radioactive gold nanoparticles (R-GNPs) are disclosed. The method comprises: a) providing a solution comprising gold (Au-197) ions; and b) exposing the solution to neutron irradiation to generate a composition comprising non-ionic R-GNPs. Alternatively, the method comprises: a) providing a solution that comprises a composition comprising gold (Au-197) nanoparticles (GNPs); and b) exposing the GNP solution to neutron irradiation to generate a composition comprising non-ionic R-GNPs. Compositions that comprises non-ionic R-GNPs encapsulated within and/or anchored to MSNs, and methods of making the same are also disclosed.
