||Preliminary PET Study of Carbon-11 Labeled RGD Peptide by Using Carbon-11 Formaldehyde
Hanyu, Masayuki ,
Sugyou, Aya ,
Tsuji, Atsushi ,
Kawamura, Kazunori ,
Saga, Tsuneo ,
Ming-Rong, ZhangFukumura, Toshimitsu
Positron emission tomography (PET), in particular, is a useful modality that enables in vivo biological information to be obtained in a noninvasive manner using a variety of PET radiopharmaceuticals. Short half-life positron emitters have generally been used for PET molecular imaging studies. It is possible to synthesize PET probes that possess the same chemical structures as the parent unlabeled molecules without altering their biological activity because, with the exception of 18F, the positron-emitting radionuclides described above can replace their stable analogues in biomolecules. However, 15O and 13N have only ever been used in simple compounds such as [15O]O2 and [13N]NH3, respectively, because of the limitations imposed by their short half-lives. Carbon is present in all organic molecules to such an extent that the introduction of carbon-11 to a molecule does not modify its properties.The development of procedures amenable to the synthesis of novel carbon-11 labeled agents for use as tracers in biomedical research is important for moving the PET imaging technique forward into the future. A procedure for the synthesis of a 11C-labeled oligopeptide containing [1-11C]1,2,3,4-tetrahydro--carboline-3-carboxylic acid from the corresponding Trp•HCl-containing oligopeptide has been developed involving a Pictet-Spengler reaction with [11C]formaldehyde . Herein, we report the radiosynthesis and PET study of cyclic RGD ([11C]1) and cyclic RAD ([11C]2) peptide using [11C]formaldehyde. We attempted remote-controlled synthesis of [11C]1 and [11C]2 using an automatic production system for [11C]CH3I. Radiochemical yield of [11C]2 at end of synthesis was 4.3±1.5 % (n=3), and the total synthesis time was about 40 min. Further details about the tumor imaging studies by PET will be reported.