Single Molecule Imaging of Sp3 Functionalized Ultrashort Carbon Nanotubes for Deep Brain Tissue Investigation

Abstract

Near-infrared (NIR) fluorescence microscopy has attracted significant attention for in vivo deep tissue imaging due to the combination of low light scattering and absorption by the tissues, resulting in good light penetration depth, especially in the NIR-II window (~1000–1350 nm). In this context, NIR photoluminescence (PL) (λem ~ 900–1400 nm) of single-walled carbon nanotubes overlapping with the so-called “tissue transparency window” laid the foundation for their use in bioimaging and sensing applications. Interestingly, although ultrashort carbon nanotubes (usCNTs) had long been sought for their advantages of mimicking bio-molecular dimensions, it is only when sp3 defects introduced bright fluorescent usCNTs could be generated [1]. In this work, we demonstrate the efficient preparation of bright fluorescent usCNTs specifically designed for biological applications, and we show how to create bright usCNTs wrapped by a biocompatible encapsulating agent (phospholipid-polyethylene glycol, PL-PEG). More precisely, we adapted a synthesis route where the sp3 functionalization is followed by chemical cutting [2]. We will present their full characterization and demonstrate their performance for deep tissue imaging in neuroscience. More precisely, our results performed on live brain tissue allow us to analyze their length specific behaviors in different compartments of mouse brains in comparison to the long sp3 functionalized CNTs [3].