AbstractSingle-particle tracking (SPT) represents a powerful tool for revealing the single-molecule dynamics in a number of biological processes in live cells and biological tissue. Single-walled carbon nanotubes (SWCNTs) are promising photoluminescence emitters for SPT applications in various biological environments due to their characteristic large-aspect-ratio structures along with their bright and stable near-infrared (NIR) photoluminescence, which are invaluable for long-term video-rate imaging and tracking applications at the single-molecule level with high signal-to-noise ratios (SNRs). Recent advances in applying SWCNTs as NIR photoluminescence emitters have highlighted the understanding of brain tissue organization at the nanometer scale. In the first section, this review article summarizes the latest advances in different surface coatings commonly used for encapsulating SWCNT surfaces via molecular self-assembly in order to obtain surface-coated nanotubes with low cytotoxicity and minimal nonspecific interactions with live cells while maintaining their emission of bright photoluminescence to enable long-term photoluminescent imaging and tracking at the single-nanotube level in biological environments. The second section offers a comparison of different excitation strategies of (6,5) SWCNTs to determine the best excitation wavelength for efficient video-rate imaging and tracking of individual nanotubes in live brain tissue for up to tens of minutes without inducing unacceptable phototoxicity or temperature increases. Finally, this review showcases that, by utilizing the photoluminescence tracking of single nanotubes combined with super-resolution single-molecule localization microscopy technologies, it is practical to elucidate the ultrafine nanometer-scale organization of the brain extracellular space (ECS) and probe the local rheological properties of young rat brain with a subdiffraction optical resolution down to 50 nm at a subwavelength accuracy of ~40 nm. The findings primarily indicate the great diversity of the brain ECS and the inhomogeneous properties of the local viscosity in live brain tissue. Overall, because of their advantages of low cytotoxicity, bright photoluminescence, high SNRs (~25), and deep tissue penetration (~100 μm) for long-term video-rate imaging and tracking at the single-nanotube level under 845 nm excitation (K-momentum exciton–phonon sideband, KSB), phospholipid-polyethylene glycol-coated SWCNTs hold great potential as NIR photoluminescence emitters for single-particle tracking in biological environments, as exemplified here in live brain tissue, and may find extended applications in elucidating the fundamental roles of the brain ECS in various biological processes, such as sleep, memory, aging, brain tumor progression, and neurodegenerative disease development.This review summarizes the recent advances in surface-coated single-walled carbon nanotubes as near-infrared nanometer-sized photoluminescent emitters for single-particle imaging and tracking applications in complex biological environments. It is focused on demonstrating surface coating identification, excitation strategies comparison, and long-term single-nanotube tracking inside the brain extracellular space in the live brain tissue.

中文翻译：

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表面涂层单壁碳纳米管作为近红外光致发光发射器的进展，用于生物环境中的单粒子跟踪应用

摘要单粒子追踪 (SPT) 是揭示活细胞和生物组织中许多生物过程中单分子动力学的有力工具。单壁碳纳米管 (SWCNT) 由于其特有的大纵横比结构以及明亮稳定的近红外 (NIR) 光致发光，在各种生物环境中成为 SPT 应用的有前途的光致发光发射器，这对于长期而言是无价的具有高信噪比 (SNR) 的单分子水平的视频速率成像和跟踪应用。应用 SWCNT 作为 NIR 光致发光发射器的最新进展突出了对纳米级脑组织组织的理解。在第一节中，这篇综述文章总结了通常用于通过分子自组装封装 SWCNT 表面的不同表面涂层的最新进展，以获得具有低细胞毒性和最小与活细胞非特异性相互作用的表面涂层纳米管，同时保持它们发射明亮的光致发光以实现长期- 生物环境中单纳米管水平的光致发光成像和跟踪。第二部分提供了 (6,5) SWCNT 的不同激发策略的比较，以确定最佳激发波长，以在不引起不可接受的光毒性或温度的情况下，对活脑组织中的单个纳米管进行有效的视频速率成像和跟踪长达数十分钟增加。最后，这篇评论表明，利用单纳米管的光致发光跟踪结合超分辨率单分子定位显微技术，阐明脑细胞外空间（ECS）的超细纳米级组织和探测幼鼠脑的局部流变学特性是切实可行的。次衍射光学分辨率低至 50 nm，亚波长精度约为 40 nm。研究结果主要表明脑 ECS 的巨大多样性和活脑组织中局部粘度的不均匀特性。总体而言，由于它们具有低细胞毒性、明亮的光致发光、高信噪比 (~25) 和深层组织穿透 (~100 μm) 的优势，可在 845 nm 激发下在单纳米管水平进行长期视频速率成像和跟踪。 K-动量激子-声子边带，KSB)，磷脂-聚乙二醇涂层的 SWCNT 作为 NIR 光致发光发射器具有巨大的潜力，可用于生物环境中的单粒子跟踪，如这里在活脑组织中的例子，并且可能会在阐明脑 ECS 在各种生物过程中的基本作用方面有广泛的应用，例如睡眠、记忆、衰老、脑肿瘤进展和神经退行性疾病的发展。这篇综述总结了表面涂层单壁碳纳米管作为近红外纳米尺寸光致发光发射器的最新进展，用于单粒子成像和跟踪应用复杂的生物环境。它的重点是展示活脑组织中大脑细胞外空间内的表面涂层识别、激发策略比较和长期单纳米管跟踪。