Subcellular Targeted Nanohoop for One- and Two-Photon Live Cell Imaging

Abstract

Fluorophores are powerful tools for interrogating biological systems. Carbon nanotubes (CNTs) have long been attractive materials for biological imaging due to their nearinfrared 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.

Photostable polymorphic organic cages for targeted live cell imaging

“… 36 Moreover, an intracellular targeted macrocyclic nanohoop showed fast cell uptake and two-photon live cell fluorescence imaging. 37 In this work, a tautomeric organic cage (OC1) that shows unprecedented photostability for live-cell imaging with high biocompatibility, cell permeability and mitochondrial targetability is reported ( Fig. 1 ).…”

“…The quantum yield of OC1 in DMSO are about half that of in chloroform that is significantly matched with the reported intracellular targeted macrocyclic nanohoop structure. 37 The fluorescent properties of OC1 were maintained at different pH values (4, 7 and 10) (Fig. S15 † ).…”

Versatile carbon nanoplatforms for cancer treatment and diagnosis: strategies, applications and future perspectives

“…CNTs can be applied in various cancer imaging techniques like MRI, PAI, Raman imaging, ultrasonography, radionuclide imaging and NIR fluorescence imaging 155 . For instance, Lovell et al reported a sort of CNTs-based nanohoop that could generate fluorescence for in vivo cervical carcinoma cell imaging 156 . Coating noble metals around the surface of CNTs is often used to improve their Raman signals 157 .…”

Modular synthesis, racemization pathway, and photophysical properties of asymmetrically substituted cycloparaphenylenes

“…Conjugated macrocycles with closed circuits and delocalized p-electrons have been of longstanding interest owing to their optical, magnetic, and electronic properties. 1,2 Of this broad scope, cycloparaphenylenes (CPPs), or carbon nanohoops, which possess the simplest cyclic structural unit of armchair carbon nanotubes (CNTs), have recently emerged as a new class of strained, non-planar aromatic molecules 3,4 with exciting potential applications as solution-/solid-state fluorophores and sensors, 5,6 organic electronic components, 7 microporous materials, 8 and building blocks for atomically precise CNT mimics. 9,10 Despite their simple structure, however, the synthesis of CPPs was only achieved in 2008 from curved precursors after pursuit for more than half a century.…”