Novel Receptor-targeted Fluorescent Contrast Agents for in Vivo Tumor Imaging

Rationale And Objectives: To evaluate the efficacy of a novel tumor receptor-specific small-peptide-near-infrared dye conjugate for tumor detection by optical imaging.

Methods: A novel, near-infrared dye-peptide conjugate was synthesized and evaluated for tumor-targeting efficacy in a well-characterized rat tumor model (CA20948) known to express receptors for the chosen peptide. A simple continuous-wave optical imaging system, consisting of a near-infrared laser diode, a cooled CCD camera, and an interference filter, was used in this study.

Results: Tumor retention of two non-tumor-specific dyes, indocyanine green and its derivatized analogue, bis-propanoic acid cyanine dye (cypate), was negligible. In contrast, the receptor-specific peptide-cypate conjugate (cytate) was retained in the CA20948 tumor, with an excellent tumor-tonormal-tissue ratio in the six rats examined.

Conclusions: Optical detection of tumors with a receptor-targeted fluorescent contrast agent has been demonstrated. This result represents a new direction in cancer diagnosis and patient management.