Recent Trends in the Nucleophilic [ 18 F]-radiolabeling Method with No-carrier-added [ 18 F]fluoride
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REVIEW ARTICLE
Recent Trends in the Nucleophilic [18F]-radiolabeling Method with No-carrier-added [18F]fluoride Dong Wook Kim & Hwan-Jeong Jeong & Seok Tae Lim & Myung-Hee Sohn
Received: 20 November 2009 / Revised: 24 November 2009 / Accepted: 26 November 2009 / Published online: 26 February 2010 # Korean Society of Nuclear Medicine 2010
Abstract Noninvasive imaging in living subjects with positron emission tomography (PET) provides early detection of diseases in humans. For this application, it is necessary to prepare specific molecular imaging probes labeled with positron-emitting radioisotopes such as fluorine-18 for obtaining high-quality PET imaging. In this review, we describe recent trends in the F-18 radiolabeling method for the introduction of no-carrier-added fluorine-18, which was obtained from an 18O(p,n)18F reaction, into a specific molecular site, which in turn is intended to serve as an imaging agent for PET study. These labeling protocols are based on ionic liquid media 18F radiofluorination in the presence of some water, enzymatic 18F fluorination using fluorinase in water solution, non-polar protic alcohol media 18 F radiofluorination and its mechanism, and nucleophilic 18 F fluorination of an aromatic iodonium salt precursor. Keywords Nucleophilic fluorination . Fluorine-18 . Ionic liquid . Tert alcohol . Fluorinase . Iodonium salts
D. W. Kim : H.-J. Jeong : S. T. Lim : M.-H. Sohn Department of Nuclear Medicine, Cyclotron Research Center, Research Institute of Clinical Medicine, Chonbuk National University Medical School, Jeonju, Jeonbuk 561-712, Korea D. W. Kim (*) Department of Nuclear Medicine, Cyclotron Research Center, Chonbuk National University Medical School, Jeonju, Jeonbuk 561-712, Korea e-mail: [email protected]
Introduction Positron emission tomography (PET) has been widely used in the medical imaging of molecular and biological processes, and provides promising opportunities to monitor metabolism and detect diseases in humans [1]. It is necessary to prepare specific molecular imaging probes labeled with positron-emitting radioisotopes for obtaining high-quality PET imaging [1, 2]. For this application, in particular fluorine-18 has many desirable characteristics: 18 F-Radiolabeled biologically active compounds, such as peptides, neuro-transmitter ligands, and enzyme inhibitor analogues, can be used to trace biochemical processes while maintaining favorable interaction with the target since fluorine-18 can afford minimal steric interference; its relatively long half-life (t1/2 =110 min) can allow [18F]labeled radiopharmaceuticals to be produced regionally and shipped for imaging studies to nearby hospitals that are not equipped with cyclotrons for radionuclide production; the [18F]fluorine atom can form stable bonding to carbon at the molecular level; finally, fluorine-18 can be produced easily from cyclotron via irradiation of [18O] water targets with proton beams [3]. However, despite the many desirable characteristics of fluorine-18, only a few [18F]-radiolabeling processes ar
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