Abstract: A biomedical device assembly, such as a stent, for the targeted treatment of a tissue, such as the inhibition of restentosis. The stent is coated with an antigen, which is an example of a lock. The antigen can be bound by a labelled antibody, which is an example of a key and an effector. The antibody is preferably labelled with a radioactive source. According to one method of preparing the biomedical device assembly, after the stent has been placed in the blood vessel of the subject, the antibody is injected. The antibody then binds to the antigen on the stent, thereby localizing the radioactive source to the area to be treated, for example for restenosis. Other biomedical devices, such as a coil, an artificial valve or a vascular graft, could also be used in the place of the stent. The biomedical device could be placed in another biological passageway, such as the gastrointestinal tract, an airway or the genitourinary tract.