A fast tumor‐targeting near‐infrared fluorescent probe based on bombesin analog for in vivo tumor imaging

Bombesin (BBN), an analog of gastrin‐releasing peptide (GRP), of which the receptors are over‐expressed on various tumor cells, is able to bind to GRP receptor specifically. In this study, a near‐infrared fluorescent dye (MPA) and polyethylene glycol (PEG) were conjugated to BBN analog to form BBN[7–14]–MPA and BBN[7–14]–SA–PEG–MPA. The successful synthesis of the two probes was proved by the characterization via sodium dodecylsulfate–polyacrylamide gel electrophoresis, infrared and optical spectra. Cellular uptakes studies indicated that BBN‐based probes were mediated by gastrin‐releasing peptide receptors (GRPR) on tumor cells and the PEG modified probe had higher affinity. The dynamic distribution and clearance investigations showed that the BBN‐based probes were eliminated by the liver–kidney pathway. Furthermore, both of the BBN‐based probes displayed tumor‐targeting ability in GRPR over‐expressed tumor‐bearing mice. The PEG modified probe exhibited faster and higher tumor targeting capability than BBN[7–14]–MPA. The results implied that BBN[7–14]–SA–PEG–MPA could act as an effective fluorescence probe for tumor imaging. Copyright © 2014 John Wiley & Sons, Ltd.