Sub‐10 nm Radiolabeled Barium Sulfate Nanoparticles as Carriers for Theranostic Applications and Targeted Alpha Therapy

The treatment of cancer patients with α‐particle‐emitting therapeutics continues to gain in importance and relevance. The range of radiopharmaceutically relevant α‐emitters is limited to a few radionuclides, as stable chelators or carrier systems for safe transport of the radioactive cargo are often lacking. Encapsulation of α‐emitters into solid inorganic systems can help to diversify the portfolio of candidate radionuclides, provided, that these nanomaterials effectively retain both the parent and the recoil daughters. We therefore focus on designing stable and defined nanocarrier‐based systems for various clinically relevant radionuclides, including the promising α‐emitting radionuclide (224)Ra. Hence, sub‐10 nm barium sulfate nanocontainers were prepared and different radiometals like (89)Zr, (111)In, (131)Ba, (177)Lu or (224)Ra were incorporated. Our system shows stabilities of >90 % regarding the radiometal release from the BaSO(4) matrix. Furthermore, we confirm the presence of surface‐exposed amine functionalities as well as the formation of a biomolecular corona.