An improved method of 18F peptide labeling: hydrazone formation with HYNIC-conjugated c(RGDyK).
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.
Lee
Yun-Sang
YS
Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul 110-744, Korea.
Jeong
Jae Min
JM
Kim
Hyung Woo
HW
Chang
Young Soo
YS
Kim
Young Joo
YJ
Hong
Mee Kyung
MK
Rai
Ganesha B
GB
Chi
Dae Yoon
DY
Kang
Won Jun
WJ
Kang
Joo Hyun
JH
Lee
Dong Soo
DS
Chung
June-Key
JK
Lee
Myung Chul
MC
Suh
Young-Ger
YG
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
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