Theranostics 2018; 8(15):4141-4151. doi:10.7150/thno.27995 This issue


Near-Infrared-II (NIR-II) Bioimaging via Off-Peak NIR-I Fluorescence Emission

Shoujun Zhu1, Bryant C. Yung1, Swati Chandra1, Gang Niu1, Alexander L. Antaris2✉, Xiaoyuan Chen1✉

1. Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health (NIH), 35A Convent Dr, Bethesda, Maryland 20892, United States
2. Intuitive Surgical, Kifer Rd, Sunnyvale, CA 94086, United States

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Zhu S, Yung BC, Chandra S, Niu G, Antaris AL, Chen X. Near-Infrared-II (NIR-II) Bioimaging via Off-Peak NIR-I Fluorescence Emission. Theranostics 2018; 8(15):4141-4151. doi:10.7150/thno.27995. Available from

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Graphic abstract

Significantly reduced photon scattering and minimal tissue autofluorescence levels in the second biological transparency window (NIR-II; 1000-1700 nm) facilitate higher resolution in vivo biological imaging compared to tradition NIR fluorophores (~700-900 nm). However, the existing palette of NIR-II fluorescent agents including semiconducting inorganic nanomaterials and recently introduced small-molecule organic dyes face significant technical and regulatory hurdles prior to clinical translation. Fortunately, recent spectroscopic characterization of NIR-I dyes (e.g., indocyanine green (ICG), IRDye800CW and IR-12N3) revealed long non-negligible emission tails reaching past 1500 nm. Repurposing the most widely used NIR dye in medicine, in addition to those in the midst of clinical trials creates an accelerated pathway for NIR-II clinical translation. This review focuses on the significant advantage of imaging past 1000 nm with NIR-I fluorophores from both a basic and clinical viewpoint. We further discuss optimizing NIR-I dyes around their NIR-II/shortwave infrared (SWIR) emission, NIR-II emission tail characteristics and prospects of NIR-II imaging with clinically available and commercially available dyes.

Keywords: near-infrared-II (NIR-II) bioimaging, NIR dyes, tail emission, cyanine dyes, ICG/IRDye800/IR-12N3