The invention is directed to providing a compound for treating cancer, the compound comprising a metal complex having predetermined characteristics, and which may be incorporated into a polymeric nanoparticle or other delivery system for delivering the metal complex for action on tumor cells. The metal complex for treating cancer wherein the metal complex is a silver(I) salt, a silver(I) macrocyclic metal complex, a silver(I) N-heterocyclic carbene or mixtures thereof. The invention is also directed to a silver(I) macrocyclic metal complex and a silver(I) N-heterocyclic carbine, and methods of treating cancerous cells in a mammal including the steps of administering an effective amount of a silver(I) metal salt, such as by incorporating the material into a biodegradable polymeric nanoparticle.
