Synthesis of a Novel L-Methyl-Methionine-ICG-Der-02 Fluorescent Probe for In Vivo Near Infrared Imaging of Tumors

Purpose: A novel near infrared fluorescent probe, l-methyl-methionine (Met)-ICG-Der-02, was synthesized and characterized for in vivo imaging of tumors and early diagnosis of cancers. Method: Met was conjugated with ICG-Der-02 dye through the amide bond function by ethyl-3-(3-dimethyllaminopropyl) carbodiimide hydrochloride/N-hydroxysuccinimide catalysis chemistry. Met-ICG-Der-02 probe uptake was evaluated on PC3, MDA-MB-231, and human embryonic lung fibroblast cell lines. The dynamics of Met-ICG-Der-02 was investigated in athymic nude mice prior to evaluation of the probe targeting capability in prostate and breast cancer models. Results: Met-ICG-Der-02 was successfully synthesized. Cell experiments demonstrated excellent cellular uptake of Met-ICG-Der-02 on cancer cell lines without cytotoxicity. Optical imaging showed a distinguishable fluorescence signal in the tumor area at 2 h while maximal tumor-to-normal tissue contrast ratio was at 12 h Met-ICG-Der-02 post-injection. Additionally, dynamic study of the probe indicated intestinal and liver-kidney clearance pathways. Conclusion: Met-ICG-Der-02 probe is a promising optical imaging agent for tumor diagnosis, especially in their early stage.