Near-infrared fluorescent divalent RGD ligand for integrin αvβ3-targeted optical imaging

A new near-infrared fluorescent compound containing two cyclic RGD motifs, cypate-[c(RGDfK)]2 (1), was synthesized based on a carbocyanine fluorophore bearing two carboxylic acid groups (cypate) for integrin αvβ3-targeting. Compared with its monovalent counterpart cypate-c(RGDfK) (2), 1 exhibited remarkable improvements in integrin αvβ3 binding affinity and tumor uptake in nude mice of A549. The results suggest that cypate-linked divalent ligands can serve as an important molecular platform for exploring receptor-targeted optical imaging and treatment of various diseases.