Self-assembled PEG-IR-780-C13 micelle as a targeting,safe and highly-effective photothermal agent for in vivo imaging and cancer therapy

IR-780, a representative hydrophobic near-infrared (NIR) fluorescence dye, is capable of fluorescently imaging and photothermal therapy in vitro and in vivo. However, insolubility in all pharmaceutically acceptable solvents limits its further biological applications. To increase solubility, we developed a novel self-assembled IR-780 containing micelle (PEG-IR-780-C13) based on the structural modification of IR-780. Briefly, a hydrophilic PEG₂₀₀₀ was modified on the one side of IR-780, and the hydrophobic carbon chain on the other side was extended from C3 to C16 (additional C13 carbon chain). The modification provides a better self-assemble capability, improved water solubility and higher stability. In addition, PEG-IR-780-C13 micelles are specifically targeted to the tumor after intravenous injection and can be used for tumor imaging. The in vitro cell viability assays and in vivo photothermal therapy experiments indicated that CT-26 cells or CT-26 xenograft tumors can be effectively ablated by combining PEG-IR-780-C13 micelles with 808 nm laser irradiation. More importantly, no significant toxicity can be observed after intravenous administration of the therapeutic dose of generated micelles. Overall, our micelles may have the least safety concern while showing excellent treatment efficacy, and thus may be a new photothermal agent potentially useful in clinical applications.