A GRPR-targeted near-infrared fluorescent probe for precise tumor imaging and intraoperative surgical navigation

Fluorescence-guided surgery requires tumor-imaging probes that provide reliable contrast while minimizing background interference. Herein, we developed a gastrin-releasing peptide receptor (GRPR)-targeted near-infrared (NIR) fluorescent probe, IR783-BBN, by covalently conjugating the bombesin peptide with the IR783 fluorophore. This molecular design was intended to combine the tumor-targeting potential of bombesin (BBN) with the NIR imaging capability of IR783. IR783-BBN was successfully synthesized and exhibited absorption and emission maxima at 801 and 820 nm, respectively. In vitro studies demonstrated that the probe cell viability remained above 82% under the tested conditions and was internalized by 4T1 breast cancer cells in a time- and concentration-dependent manner. In 4T1 tumor-bearing mice, IR783-BBN generated detectable tumor-associated fluorescence after systemic administration, with a tumor-to-muscle fluorescence ratio of 6.97 at 1 h post-injection (n = 3). Histological and fluorescence microscopic analyses of the excised tissues further supported the correspondence between fluorescence signals and tumor-containing specimens. Overall, these findings support the feasibility of IR783-BBN as a BBN-conjugated NIR fluorescent probe for tumor imaging and fluorescence-guided surgical navigation.