Prosthetic compounds are disclosed that are effective for radiolabeling biomolecules with 18F. Representative biomolecules include antibodies (e.g., monoclonal antibodies (mAbs) and nanobodies (sdAbs)), antibody fragments, and peptides that may have an affinity for particular types of cells, such as cancer cells. The prosthetic compounds effectively address the art-recognized difficulties associated with the retention of radioactivity within the targeted cells, due to internalization of the biomolecule, followed by proteolytic degradation. Representative prosthetic compounds include (i) a succinimidyloxycarbonyl moiety, (ii) a radioactive moiety bearing 18F, and (iii) a charged moiety, i.e., a moiety that is charged under the physiological conditions of the internal cell environment.
