In vivo imaging in the second near-infrared window (NIR-II, 1000−1700 nm), which enables us to look deeply into living subjects, is producing marvelous opportunities for biomedical research and clinical applications. Very recently, there has been an upsurge of interdisciplinary studies focusing on developing versatile types of inorganic/organic fluorophores that can be used for noninvasive NIR-IIa/IIb imaging (NIR-IIa, 1300−1400 nm; NIR-IIb, 1500−1700 nm) with near-zero tissue autofluorescence and deeper tissue penetration. This review provides an overview of the reports published to date on the design, properties, molecular imaging, and theranostics of inorganic/organic NIR-IIa/IIb fluorophores. First, we summarize the design concepts of the up-to-date functional NIR-IIa/IIb biomaterials, in the order of single-walled carbon nanotubes (SWCNTs), quantum dots (QDs), rare-earthdoped nanoparticles (RENPs), and organic fluorophores (OFs). Then, these novel imaging modalities and versatile biomedical applications brought by these superior fluorescent properties are reviewed. Finally, challenges and perspectives for future clinical translation, aiming at boosting the clinical application progress of NIR-IIa and NIR-IIb imaging technology are highlighted.

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Complete excision of the last remaining 1–2% of tumor tissue without collateral damage remains particularly challenging. Herein, we report thiophenthiadiazole (TTD)-derived fluorophores L6-PEG nk (n = 1, 2, 5) as new-generation NIR-II (1000–1700 nm) probes with exceptional nonfouling performance and significantly high fluorescence quantum yields in water. L6-PEG 2k can self-assemble into vesicular micelles and exhibited minimal immunogenicity, low binding affinities, ultralong blood circulation (t 1/2 = 59.5 h), and a supercontrast ratio in vivo. Most importantly, L6-PEG 2k achieved excellent in vivo CT-26 and U87MG tumor targeting and accumulation (>20 d) through intraperitoneal or intravenous injection. A subcutaneous U87MG tumor and orthotopic brain glioma were successfully resected under NIR-II FIGS in our animal model via intraperitoneal injection in an extended time window (48–144 h). This study highlights the potential of using L6-PEG 2K as self-assembling molecular probes with long-circulation persistence for routine preoperative tumor assessment and precise intraoperative image-guided resection.

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