title: An improved method of 18F peptide labeling: hydrazone formation with HYNIC-conjugated c(RGDyK).
abstract: Radiolabeled alpha(v)beta(3)-integrin antagonists are increasingly investigated as a means of imaging angiogenesis. Several methods of labeling alpha(v)beta(3)-integrin binding peptide with (18)F have been reported recently. In the present study, we devised a straightforward means for labeling Arg-Gly-Asp (RGD) peptide with (18)F via hydrazone formation between c(RGDyK)-hydrazinonicotinic acid (HYNIC) (3) and 4-[(18)F]-fluorobenzaldehyde ([(18)F]4). The resulting reaction mixture was purified by HPLC to give 4'-[(18)F]-fluorobenzylidenehydrazone-6-nicotinamide-c(RGDyK) ([(18)F]5). The conjugation efficiency of 3 and 4 to form [(18)F]5 was 95.2%, and the radiochemical purity of [(18)F]5 after purification was >99%. The specific activity of [(18)F]5 estimated by radio-HPLC was 20.5 GBq/mumol (end of synthesis). Competitive binding assay of c(RGDyK) (1) and 5 was performed using [(125)I]iodo-c(RGDyK) as a radioligand, and K(i) values were found to be 2.8 and 21.7 nM, respectively. For the biodistribution study, the angiogenic mouse model was established by inducing unilateral ischemia on the left hindlimbs of ICR mice after femoral artery ablation. Seven days after inducing ischemia, [(18)F]5 was administered to the mice through the tail vein. Ischemic muscle uptake of [(18)F]5 was significantly higher than that of normal muscle (P<.01). Specific uptake was confirmed by coinjection of 1 with [(18)F]5. Here, we successfully labeled RGD peptide with (18)F via hydrazone formation between 3 and 4, resulting to [(18)F]5. [(18)F]5 was found to have high affinity for alpha(v)beta(3)-integrin and to accumulate specifically in ischemic hindlimb muscle of mice. We suggest that (18)F labeling via formation of hydrazone between HYNIC peptide and [(18)F]4 is a useful method for labeling c(RGDyK), which can be applied for imaging angiogenesis.
authors.affiliation: Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul 110-744, Korea.
authors.forename: Yun-Sang
authors.initials: YS
authors.lastname: Lee
authors.forename: Jae Min
authors.initials: JM
authors.lastname: Jeong
authors.forename: Hyung Woo
authors.initials: HW
authors.lastname: Kim
authors.forename: Young Soo
authors.initials: YS
authors.lastname: Chang
authors.forename: Young Joo
authors.initials: YJ
authors.lastname: Kim
authors.forename: Mee Kyung
authors.initials: MK
authors.lastname: Hong
authors.forename: Ganesha B
authors.initials: GB
authors.lastname: Rai
authors.forename: Dae Yoon
authors.initials: DY
authors.lastname: Chi
authors.forename: Won Jun
authors.initials: WJ
authors.lastname: Kang
authors.forename: Joo Hyun
authors.initials: JH
authors.lastname: Kang
authors.forename: Dong Soo
authors.initials: DS
authors.lastname: Lee
authors.forename: June-Key
authors.initials: JK
authors.lastname: Chung
authors.forename: Myung Chul
authors.initials: MC
authors.lastname: Lee
authors.forename: Young-Ger
authors.initials: YG
authors.lastname: Suh
mesh_terms: D000818:Animals; D005462:Fluorine Radioisotopes / Q000737:chemistry / Q000493:pharmacokinetics; D006834:Hydrazines / Q000737:chemistry / Q000493:pharmacokinetics; D006835:Hydrazones / Q000737:chemistry / Q000493:pharmacokinetics; D039302:Integrin alphaVbeta3 / Q000737:chemistry / Q000378:metabolism*; D007511:Ischemia / Q000000981:diagnostic imaging* / Q000378:metabolism*; D007553:Isotope Labeling / Q000379:methods; D008657:Metabolic Clearance Rate; D051379:Mice; D018482:Muscle, Skeletal / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000378:metabolism*; D009539:Nicotinic Acids / Q000737:chemistry / Q000493:pharmacokinetics; D009842:Oligopeptides / Q000737:chemistry / Q000493:pharmacokinetics*; D009928:Organ Specificity; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000493:pharmacokinetics; D014018:Tissue Distribution
chemical_list: C120392:6-hydrazinopyridine-3-carboxylic acid; D005462:Fluorine Radioisotopes; D006834:Hydrazines; D006835:Hydrazones; D039302:Integrin alphaVbeta3; D009539:Nicotinic Acids; D009842:Oligopeptides; D019275:Radiopharmaceuticals; C047981:arginyl-glycyl-aspartic acid