PRODUCTION AND CHARACTERIZATION OF99mTc AND 126I RADIOENDOFULLERENES. Michael G. Mitch, Lisa R. Karam, and Bert M. Coursey, Ionizing Radiation Division, Building 245, Room C229, NIST, Gaithersburg, MD, USA. (301-975-5491, email:mitch@mailserver.nist.gov)

We report on progress toward the development of a new class of radiotracers/ radioimagers based on fullerenes. Radioendofullerenes have radionuclides trapped inside their carbon cages, isolating chemically reactive isotopes from their environment. Radioendofullerenes, alone or with an attached biomolecule "hook", could be used in future tracing and imaging applications. The Kratschmer-Huffman method of fullerene synthesis was carried out in a Fullerene Production Chamber (FPC) using high-current arc-burning of graphite rods doped with a99mTc-saline solution or iodoform (CHI3). Fullerenes were extracted from the resulting soot by stirring in CS2. High Performance Liquid Chromatography (HPLC) was utilized to separate different fullerene species prior to characterization by optical absorption spectroscopy and non-coincident MultiPhoton Detection (ncMPD). Fullerenes were also separated by Thin Layer Chromatography (TLC) prior to Fuji plate phosphoimaging. Based on observed HPLC retention times and TLC migration distances, ncMPD and Fuji plate data strongly suggest the formation of99mTc@C60 and 99mTc@C70, direct encapsulation of a radionuclide during fullerene formation. Following production of fullerenes with a CHI3-doped graphite rod, the radionuclide 126I was produced by the reaction 127I(gamma, n)126I upon irradiation of the sample with 25 MeV electrons/bremsstrahlung radiation from the Medical Industrial Radiation Facility (MIRF). Detection of the radiolabel by ncMPD and phosphoimaging after separation by HPLC and TLC allowed identification of possible I@Cn species. This study illustrates the production of radioendofullerenes by both direct encapsulation of a radionuclide and isotope conversion following endofullerene formation.