Cysteine-Specific 18F and NIR Dual Labeling of Peptides via Vinyltetrazine Bioorthogonal Conjugation for Molecular Imaging

Radiolabeled peptides are vital for positron emission tomography (PET) imaging, yet the ¹⁸F-labeling peptides remain challenging due to harsh conditions and time-consuming premodification requirements. Herein, we developed a novel vinyltetrazine-mediated bioorthogonal approach for highly efficient ¹⁸F-radiolabeling of a native peptide under mild conditions. This approach enabled radiosynthesis of various tumor-targeting PET tracers, including targeting the neurofibromin receptor (¹⁸F-P10a), the integrin α_vβ₃ (¹⁸F-P12a), and the platelet-derived growth factor receptor β (¹⁸F-Z_PDGFRβ), with a radiochemical yield exceeding 90%. Preliminary evaluations revealed excellent hydrophilicity across these tracers, with ¹⁸F-P12a effectively visualizing integrin α_vβ₃ expression (tumor uptake: 1.57 ± 0.54%ID/g at 2 h). Additionally, we explored the potential for development of PET/near-infrared (NIR) dual-labeling agents using this method. The dual-modality agent ¹⁸F-Cy5-P12d enables specificity and colocalized imaging integrin α_vβ₃ expression (tumor uptake: 1.35 ± 0.24%ID/g at 2 h). Overall, this strategy offers a versatile platform for peptide radiolabeling and dual-modality agent development.