One-step 18F-labeling of peptides for positron emission tomography imaging using the SiFA methodology (original) (raw)
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Bioconjugate Chemistry, 2009
Radiosyntheses of 18 F-radiopharmaceuticals for positron emission tomography (PET) normally require an extraordinarily high effort of technical equipment and specially trained personnel. We recently reported a novel method for the introduction of fluorine-18 into peptides for PET-imaging based on silicon-18 F-chemistry (SiFA technique). We herewith introduce the first SiFA-based Kit-like radio-fluorination of a protein (rat serum albumin, RSA) and demonstrate its usefulness for in vivo imaging with µPET in normal rats as well as in a rat heterotropic transplanted heart model. As a labeling agent, we prepared 4-(di-tert-butyl[ 18 F]fluorosilyl)benzenethiol (Si[ 18 F]FA-SH) by simple isotopic exchange in 40-60% radiochemical yield (RCY) and coupled it directly to a Sulfo-SMCC derivatized RSA in an overall RCY of 12% within 20-30 min. The technically simple labeling procedure does not require any elaborated purification procedures and is a straightforward example of a successful application of Si-18 F chemistry for in vivo imaging with PET.
Protein labeling with the labeling precursor [18F]SiFA-SH for positron emission tomography
Nature Protocols, 2012
proteins previously derivatized with the cross-coupling reagent sulfo-sMcc (4-(N-maleimidomethyl)cyclohexane-1-carboxylic acid 3-sulfo-N-hydroxy-succinimide ester sodium salt) can be easily labeled in high radiochemical yields with the silicon-fluoride acceptor (siFa) reagent [ 18 F]siFa-sH, obtained via isotopic exchange, by thiol-maleimide coupling chemistry (n = 10). the specific activity of siFa-sH obtained in a one-step labeling reaction was >18.5 GBq mol − 1 (>500 ci mmol − 1). the number of siFa building blocks per protein molecule is defined by the previously introduced number of maleimide groups, which can be determined by a simple and convenient ellman's assay. not more than two maleimide groups are introduced using sulfo-sMcc, thereby keeping the modification of the protein low and preserving its biological activity.
Using 5-deoxy-5-[18F]fluororibose to glycosylate peptides for positron emission tomography
Nature Protocols, 2013
so far seven peptide-based 18 F-radiopharmaceuticals for diagnostic applications with positron emission tomography (pet) have entered into clinical trials. three candidates out of these seven are glycosylated peptides, which may be explained by the beneficial influence of glycosylation on in vivo pharmacokinetics of peptide tracers. this protocol describes the method for labeling peptides with 5-deoxy-5-[ 18 F]fluororibose ([ 18 F]FDr) as a prosthetic group. the synthesis of [ 18 F]FDr is effected by a nucleophilic fluorination step by using dried Kryptofix 2.2.2-K 2 co 3 -K 18 F complex and a subsequent Hcl-catalyzed hydrolysis. the conjugation of [ 18 F]FDr to the n-terminus aminooxy (-onH 2 )-functionalized peptides is carried out in anilinium buffer at pH 4.6 and at room temperature (rt, 21-23 °c), with the concentration of peptide precursors being 0.3 mM. the procedure takes about 120 min and includes two cartridge isolation steps and two reversed-phase (rp) Hplc purification steps. the quaternary methyl amine (QMa) anion exchange cartridge and the hydrophilic-lipophilic balanced (HlB) cartridge are used for the isolation of 18 F-fluoride and [ 18 F]FDr-conjugated peptides, respectively. the first Hplc purification provides the 18 F-fluorinated precursor of [ 18 F]FDr and the second Hplc purification is to separate labeled peptides from their unlabeled precursors. the final product is formulated in pBs ready for injection, with a radiochemical purity of >98% and a radiochemical yield (rcY) of 27-37% starting from the end of bombardment (eoB). the carbohydrate nature of [ 18 F]FDr and the operational convenience of this protocol should facilitate its general use. protocol nature protocols | VOL.9 NO.1 | 2014 | 139 protocol nature protocols | VOL.9 NO.1 | 2014 | 141
2000
First and foremost I would like to express my sincere gratitude to my supervisor during the project Dr. Ole Kristian Hjelstuen for giving me the opportunity to explore the exiting field of PET, and for his support and critical review of my work. I am also very thankful to all scientists and staff at Discovery Research, GE Healthcare, Oslo for all help and assistance and nice lunches during these years. In particular, thanks to Joseph M. Arukwe, my organic chemistry mentor, for his good advice, positive attitude and his numerous contributions and always having his office door open for me and my never ending questions.
Bioconjugate Chemistry, 2004
18 F]Fluorothiols are a new generation of peptide labeling reagents. This article describes the preparation of suitable methanesulfonyl precursors and their use in no-carrier-added radiosyntheses of 18 F-fluorothiols. The preparations of (3-[ 18 F]fluoropropylsulfanyl)triphenylmethane, (2-{2-[2-(2-[ 18 F]fluoroethoxy)ethoxy]ethoxy}ethylsulfanyl)triphenylmethane, and 4-[ 18 F]fluoromethyl-N-[2-triphenylmethanesulfanyl)ethyl]benzamide starting from the corresponding methanesulfonyl precursors were investigated. Following the removal of the triphenylmethane protecting group, the 18 F-fluorothiols were reacted with the N-terminal chloroacetylated model peptide ClCH 2 C(O)-LysGlyPheGlyLys. The corresponding radiochemical yields of 18 F-labeled isolated model peptide, decay-corrected to 18 F fluoride, were 10%, 32%, and 1%, respectively. These results indicate a considerable potential of 18 F-fluorothiols for the chemoselective labeling of peptides as tracers for positron emission tomography (PET).