An IR820 Dye-Protein Complex for Second Near-Infrared Window and Photoacoustic Imaging

Recently, much attention has been focused on the development of second near-infrared window (NIR-II, 1000-1700 nm) fluorescence imaging because of its reduced scattering, minimal absorption, and negligible autofluorescence. NIR-II bioimaging allows the visualization of deep anatomical features with an unprecedented degree of clarity. In addition to the construction of a variety of new NIR-II fluorophores, using a fluorescence tail emission greater than 1000 nm for conventional NIR-I dyes represents a promising strategy for developing an NIR-II imaging technique. Herein, the authors report tailoring a supramolecular assembly of human serum albumin (HSA) protein complexed with a sulfonated NIR-I organic dye (IR820) to produce a brilliant 21-fold increase in fluorescence for NIR-II imaging. In vivo NIR-II imaging with IR820-HSA allows noninvasive and dynamic visualization and monitoring of physiological and pathological conditions of the vascular system, lymphatic drainage system, and tumor-bearing mice, as well as image-guided tumor resection with high spatial and temporal resolution. Furthermore, photoacoustic imaging (PAI) of IR820-HSA in mouse tumor models also demonstrate good tumor accumulation. Overall, an IR820-protein complex with high biocompatibility can be easily constructed using a conventional NIR-I dye that provides a new theranostic tool with high clinical translation potential.