Site-selective radiolabeling of peptides by 18F-fluorobenzoylation with [18F]SFB in solution and on solid phase: a comparative study
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Peptides labeled with short-lived positron-emitting radionuclides are of outstanding interest as probes for molecular imaging by positron emission tomography (PET). Herein, the site-selective incorporation of fluorine-18 into lysine-containing peptides using the prosthetic labeling agent N-succinimidyl 4-[18F]fluorobenzoate ([18F]SFB) is described. The reaction of [18F]SFB with four biologically relevant resin-bound peptides was studied and optimized. For comparison, each peptide was 18F-fluorobenzoylated in solution under different conditions and the product distribution was analyzed confirming the advantages of the solid-phase approach. The method’s feasibility for selective radiolabeling either at the N-terminus or at the lysine side chain was demonstrated. Labeling on solid phase with [18F]SFB resulted in crude 18F-fluorobenzoylpeptides whose radiochemical purities were typically greater than 90% and that could be prepared in synthesis times from 65 to 76 min.
KeywordsFluorine-18 Solid-phase synthesis Regioselectivity Positron emission tomography
The dedicated assistance of Uta Lenkeit and Peggy Wecke in the radiosynthesis of [18F]SFB is gratefully acknowledged.
Conflict of interest
The authors declare that they have no conflict of interest.
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