The significantly reduced tissue autofluorescence and scattering in the NIR‐II region (1000–1700 nm) opens many exciting avenues for detailed investigation of biological processes in vivo. However, the existing NIR‐II fluorescent agents, including many molecular dyes and inorganic nanomaterials, are primarily focused on complicated synthesis routes and unknown immunogenic responses with limited potential for clinical translation. Herein, the >1000 nm tail emission of conventional biocompatible NIR cyanine dyes with emission peaks at 700–900 nm is systematically investigated, and a type of bright dye for NIR‐II imaging with high potential for accelerating clinical translation is identified. The asymmetry of the π domain in the S₁ state of NIR cyanine dyes is proven to result in a twisted intramolecular charge‐transfer process and NIR‐II emission, establishing a general rule to guide future NIR‐I/II fluorophore synthesis. The screened NIR dyes are identified to possess a bright emission tail in the NIR‐II region along with high quantum yield, high molar‐extinction coefficient, rapid fecal excretion, and functional groups amenable for bioconjugation. As a result, NIR cyanine dyes can be used for NIR‐II imaging to afford superior contrast and real‐time imaging of several biological models, facilitating the translation of NIR‐II bioimaging to clinical theranostic applications.

中文翻译：

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重复使用花青NIR-I染料可加快近红外II（NIR-II）生物成像的临床翻译速度

NIR-II区（1000-1700 nm）中组织自发荧光和散射的显着降低为详细研究体内生物学过程开辟了许多令人兴奋的途径。但是，现有的NIR-II荧光剂，包括许多分子染料和无机纳米材料，主要集中在复杂的合成路线和未知的免疫原性反应上，具有有限的临床翻译潜力。在本文中，系统地研究了发射峰在700–900 nm的常规生物相容性NIR花青染料> 1000 nm尾发射，并确定了一种用于NIR-II成像的明亮染料，具有加速临床翻译的潜力。S _1中π域的不对称性NIR花青染料的状态被证明会导致扭曲的分子内电荷转移过程和NIR-II发射，从而确立了指导未来NIR-I / II荧光团合成的一般规则。筛选出的NIR染料在NIR-II区域具有明亮的发射尾，并具有高量子产率，高摩尔消光系数，快速粪便排泄和适合生物共轭的官能团。因此，NIR花青染料可用于NIR-II成像，以提供多种生物模型的出色对比度和实时成像，从而促进NIR-II生物成像向临床治疗学应用的转化。