Design and synthesis of a bimodal target-specific contrast agent for angiogenesis

A bimodal target-specific contrast agent based on a cyclic peptide contg. the target-specific NGR sequence, gadolinium(III) diethylenetriaminepentaacetic acid (Gd(III)DTPA), and Oregon Green 488 (OG488) suitable for both MR imaging and optical imaging of angiogenesis is developed. The synthetic strategy for this target-specific contrast agent exploits the use of highly efficient, chemoselective reactions, such as native chem. ligation, and gives a straightforward approach for double labeling of peptides in general.