Self-assembled monolayers on gold for the fabrication of radioactive stents

An innovative and easily applicable method for the fabrication of radioactive stents, to be used for the treatment of restenosis, is presented. By incorporating the β-emitting radioisotopes 186Re, 188Re, 90, or 32P into sulfur-containing adsorbates, it becomes possible to cover a gold surface with a radioactive self-assembled monolayer (SAM). Two methods have been investigated. In the first, SAMs consisting of potentially radioactive rhenium-, yttrium-, and phosphorus-containing adsorbates have been assembled on 2D gold substrates, after which they have been studied by wettability measurements, electrochemistry, and X-ray photoelectron spectroscopy (XPS). The stability of these SAMs under simulated physiological conditions (phosphate buffered saline, PBS solution) for periods up to two months has been demonstrated. Alternatively, potentially radioactive monolayers have been prepared by exposure of SAMs of mono-, bi-, and tridentate ligands to a solution containing a radiometal (rhenium) in order to bind the metal to the monolayer. The polydentate ligands exhibit excellent binding capacity, leading to SAMs containing over 10-10 mol/cm2 of the radiometal, which is more than sufficient to make this system viable for the delivery of therapeutical dosages of radiation.