Fluorophores are powerful tools for interrogating biological systems. Carbon nanotubes (CNTs) have long been attractive materials for biological imaging due to their near-infrared excitation and bright, tunable optical properties. The difficulty in synthesizing and functionalizing these materials with precision, however, has hampered progress in this area. Carbon nanohoops, which are macrocyclic CNT substructures, are carbon nanostructures that possess ideal photophysical characteristics of nanomaterials, while maintaining the precise synthesis of small molecules. However, much work remains to advance the nanohoop class of fluorophores as biological imaging agents. Herein, we report an intracellular targeted nanohoop. This fluorescent nanostructure is noncytotoxic at concentrations up to 50 μM, and cellular uptake investigations indicate internalization through endocytic pathways. Additionally, we employ this nanohoop for two-photon fluorescence imaging, demonstrating a high two-photon absorption cross-section (65 GM) and photostability comparable to a commercial probe. This work further motivates continued investigations into carbon nanohoop photophysics and their biological imaging applications.

中文翻译：

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用于单光子和双光子活细胞成像的亚细胞靶向 Nanohoop

荧光团是研究生物系统的强大工具。碳纳米管 (CNT) 长期以来一直是生物成像的有吸引力的材料，因为它们具有近红外激发和明亮、可调谐的光学特性。然而，精确合成和功能化这些材料的困难阻碍了该领域的进展。碳纳米环是大环碳纳米管亚结构，是一种碳纳米结构，具有纳米材料理想的光物理特性，同时又能保持小分子的精确合成。然而，在推进纳米环类荧光团作为生物成像剂方面还有很多工作要做。在此，我们报告了一种细胞内靶向纳米环。这种荧光纳米结构在浓度高达 50 μM 时是无细胞毒性的，和细胞摄取研究表明通过内吞途径内化。此外，我们将这种纳米环用于双光子荧光成像，展示了高双光子吸收截面 (65 GM) 和与商业探针相当的光稳定性。这项工作进一步激发了对碳纳米环光物理学及其生物成像应用的持续研究。