title: Deep-tissue anatomical imaging of mice using carbon nanotube fluorophores in the second near-infrared window.
abstract: Fluorescent imaging in the second near-infrared window (NIR II, 1-1.4 μm) holds much promise due to minimal autofluorescence and tissue scattering. Here, using well-functionalized biocompatible single-walled carbon nanotubes (SWNTs) as NIR II fluorescent imaging agents, we performed high-frame-rate video imaging of mice during intravenous injection of SWNTs and investigated the path of SWNTs through the mouse anatomy. We observed in real-time SWNT circulation through the lungs and kidneys several seconds postinjection, and spleen and liver at slightly later time points. Dynamic contrast-enhanced imaging through principal component analysis (PCA) was performed and found to greatly increase the anatomical resolution of organs as a function of time postinjection. Importantly, PCA was able to discriminate organs such as the pancreas, which could not be resolved from real-time raw images. Tissue phantom studies were performed to compare imaging in the NIR II region to the traditional NIR I biological transparency window (700-900 nm). Examination of the feature sizes of a common NIR I dye (indocyanine green) showed a more rapid loss of feature contrast and integrity with increasing feature depth as compared to SWNTs in the NIR II region. The effects of increased scattering in the NIR I versus NIR II region were confirmed by Monte Carlo simulation. In vivo fluorescence imaging in the NIR II region combined with PCA analysis may represent a powerful approach to high-resolution optical imaging through deep tissues, useful for a wide range of applications from biomedical research to disease diagnostics.
authors.affiliation: Department of Chemistry, Stanford University, 333 Campus Drive #121, Stanford, CA 94305, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Welsher
authors.forename: Sarah P
authors.initials: SP
authors.lastname: Sherlock
authors.forename: Hongjie
authors.initials: H
authors.lastname: Dai
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry; D003287:Contrast Media / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000494:pharmacology*; D007259:Infrared Rays; D007668:Kidney / Q000473:pathology; D008099:Liver / Q000473:pathology; D008168:Lung / Q000473:pathology; D051379:Mice; D018715:Microscopy, Video / Q000379:methods; D012157:Mononuclear Phagocyte System; D037742:Nanotubes, Carbon / Q000737:chemistry*; D019047:Phantoms, Imaging; D025341:Principal Component Analysis; D012542:Scattering, Radiation; D013154:Spleen / Q000473:pathology
chemical_list: D001672:Biocompatible Materials; D003287:Contrast Media; D005456:Fluorescent Dyes; D037742:Nanotubes, Carbon