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.near-infrared imaging | photoluminescence | principal component analysis imaging | dynamic contrast imaging | deep-tissue imaging

Neodymium-doped nanoparticles for infrared fluorescence bioimaging: The role of the host

“…15,16 A great variety of LNPs have been applied in biomedical research, not only for imaging but also for other purposes including drug delivery and in vitro and in vivo photothermal therapies. 17 Quantum dots (QDs), 18,19 gold NPs, 20 carbonbased NPs (C-NPs), 21,22 organic NPs, 23 and rare earth-doped nanocrystals (RENPs) 24 are among the nanoparticle-based fluorescent probes that have been successfully used in biomedicine.…”

Dual Near Infrared Two-Photon Microscopy for Deep-Tissue Dopamine Nanosensor Imaging

“…33 We deconvolve the contributions of each SWNT chirality to emission peaks using a non-linear least squares method (See Supporting Information Figures S1 & S2, Tables S1 & S2). 10 The prominent emission peaks at 1030 nm and 1126 nm are consistent with onresonance excitation of (7,5) and (7,6) chirality SWNTs, respectively, in addition to contributions from other chiralities excited off-resonance. The emission peak at 1265 nm is a convolution of (10,3), (9,5) and (11,1) chirality SWNTs excited on-resonance, along with off-resonance SWNTs.…”

“…http://dx.doi.org/10.1101/145912 doi: bioRxiv preprint first posted online Jun. 4, 2017; To demonstrate the advantages of two-photon over one-photon fluorescence imaging of SWNT-based nanosensors, we compared reconstructed images of a SWNT-filled capillary immersed in a highly scattering tissue phantom, 1% Intralipid solution, 6,8,23 under 1PE versus 2PE. Of relevance to deep-brain imaging of dopamine, the tissue phantom simulates both the absorbance due to water as well as the scattering brain tissue.…”

“…We compute the quantum yield and the two-photon absorption cross-section using (6,5) chirality SWNTs suspended in a sodium dodecyl sulfate, (SDS) using a reference dye, 3,3′-diethylthiatricarbocyanine perchlorate (DTTC), whose quantum yield and two-photon cross section are known. 32 Furthermore, we demonstrate molecular recognition of dopamine using our nanosensors and 2PE, achieving a two-fold increase in SWNT nanosensor fluorescence in the presence of 100 µM dopamine.…”

“…To further characterize 2PE emission of SWNTs, we prepared a sample enriched with (6,5) chirality dispersed SWNTs through previously reported protocols. 35 Briefly, HiPco SWNT dispersed in SDS by probe tip sonication were purified by adsorption column chromatography through separation over a series of sephacryl gel beds.…”