(339f) Single-Chirality Carbon Nanotubes for NIR Five-Dimensional Optoacoustic Imaging

Optoacoustic (OA, photoacoustic) tomography offers a unique five-dimensional imaging capacity, combining real-time, multi-spectral (multi-wavelength), and three-dimensional imaging of spectrally-distinct substances. Contrast agents with defined absorption peaks within the near-infrared window (NIR, 700-1350 nm) enable deep-tissue visualization of dynamic biological processes in vivo. However, spectral coloring effects associated with wavelength-dependent light attenuation hinder simultaneous differentiation of multiple agents, limiting the OA multiplexing capacity and restricting the full potential of this modality. One class of nanomaterials that could help overcome these limitations are semiconducting single-walled carbon nanotubes (SWCNTs), which exhibit a lattice-dependent bandgap structure known as chirality (n,m). In this study, we introduce chirality-separated carbon nanotubes as OA contrast agents characterized by narrow and tunable absorption peaks within the NIR. These sorted SWCNTs were obtained by aqueous two-phase extraction (ATPE) and later surface-modified with macromolecules to enhance their biocompatibility. The nanotubes' unique optical features enable unambiguous differentiation of multiple types of nanotubes amidst strong background signals from blood and other biological tissues, while exhibiting excellent photostability. High-frame-rate in vivo imaging of a nanotube bolus injected into the bloodstream was accomplished with only three optical wavelengths, while nanotube-coated microparticles could be individually detected and tracked. These results pave the way for innovative approaches in perfusion assessment, super-resolution imaging, and targeted drug delivery.