NIR-II Dye-Labeled Cylindrical Polymer Brushes for in Vivo Imaging

Although many types of second near-infrared (NIR-II) dyes have been developed, the NIR-II dye bearing a single reactive group, which is indispensable for specifically labeling nanomaterials or biofunctional molecules, is still lacking. In this work, a donor-acceptor-donor type NIR-II dye named IR1032 bearing an amino group was synthesized and used to covalently label cylindrical polymer brushes. The labeled polymer brushes (named brushes1032) had densely grafted poly(ethylene glycol) (PEG) chains and exhibited a wormlike morphology. In aqueous medium, brushes1032 had an emission peak at 1032 nm and a quantum yield (QY) of ∼0.13% measured with IR 26 as a reference (QY = 0.05%). We demonstrated that the dense PEG chains in brushes1032 were greatly favorable for their QY by separating the fluorophores and shielding them from the interactions with water. After being injected intravenously into tumor-bearing mice, brushes1032 showed high tumor accumulation and provided high-resolution fluorescence imaging, exhibiting great application potentials in tumor detection.