E. Smalley and his co-workers developed high-pressure carbon monoxide method
called HiPco for the synthesis of carbon nanotubes [85]. In this process, carbon
monoxide acts as a feedstock, and iron carbon monoxide Fe(CO) 5 acts as a catalyst.
With the HiPco method, the thinnest SWCNTs with high quality, few structural
defects, and high intrinsic selectivity are obtained.
5.3 Application In Vivo
Generally, SWCNTs require surface functionalization with water-soluble polymers
or proteins that allow them to be nontoxic [27, 28]. In 2009, NIR-II probes were
prepared by coating SWCNTs with phospholipid–polyethylene glycol. This indicates the beginning of the use of SWCNTs for NIR-II imaging (Fig. 22a, b)
[27]. Since then, SWCNTs have been extensively used for tumor-specific imaging
and mouse organ registration (Fig. 22c–f) [28] with higher spatial resolution than
that afforded by in vivo microCT (Fig. 22g–h) [29, 31]. In mouse cerebral vasculature NIR-II imaging, SWCNTs have shown the great promising with high spatial
(<10 μm) and temporal (<200 ms per frame) resolution, at a depth of >2 mm
(Fig. 22k) [30]. This is a truly noninvasive procedure at molecular level for real-time
dynamic cerebrovascular imaging. By laser vaporization method, SWCNTs with
smaller bandgaps and larger average diameters (up to 1.24 nm) were recently
synthesized. At a depth of up to 3 mm in mouse hindlimb, SWCNTs allow in vivo
vascular NIR-II imaging with high spatial resolution up to 4 mm. Single-vesselresolved blood flow speed mapping for multiple hindlimb arterial vessels has also
been obtained simultaneously by video-rate fluorescence NIR-II imaging (Fig. 22i, j)
[32]. Moreover, in the range up to 1,700 nm, this probe may provide highperformance in vivo NIR-IIb imaging.
By creating targeted bright NIR-II emission SWCNTs, the sensitivity can be
improved for early detection. For example, a multifunctional M13 phage has been
assembled with SWCNTs via π–π interactions for use as a ligand for targeted NIR-II
imaging of tumors. Targeting M13-SWCNTs improves the uptake up to fourfold in
prostate-specific membrane antigen-positive prostate tumors compared to
nontargeted SWCNTs. In addition, it can identify sub-mm tumors that are not easily
identified by either visible or NIR-I fluorophore [86]. Other suitable targeting
strategies, such as analyte-specific receptors, have been developed for detecting
changes in NO level in response to wound-induced tissue inflammation (Fig. 22l)
[33]. In one study, SWCNTs have great promising application in NIR-II imaging
guidance for cancer resection [86]. In this research, many sub-millimeter tumor
nodules are discovered in NIR-II image-guided system compared with non-imageguided system. In addition, NIR-II imaging observes low tissue autofluorescence,
which enhances target-to-background ratios and allows detection of small tumor
nodules in confined anatomic regions. However, SWCNTs have a broad absorbance
overlap in the NIR-II region, which may cause NIR-II loss. Then, how to increase the
quantum yields will be a major focus for SWCNTs application in vivo.
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S. He and Z. Cheng
called HiPco for the synthesis of carbon nanotubes [85]. In this process, carbon
monoxide acts as a feedstock, and iron carbon monoxide Fe(CO) 5 acts as a catalyst.
With the HiPco method, the thinnest SWCNTs with high quality, few structural
defects, and high intrinsic selectivity are obtained.
5.3 Application In Vivo
Generally, SWCNTs require surface functionalization with water-soluble polymers
or proteins that allow them to be nontoxic [27, 28]. In 2009, NIR-II probes were
prepared by coating SWCNTs with phospholipid–polyethylene glycol. This indicates the beginning of the use of SWCNTs for NIR-II imaging (Fig. 22a, b)
[27]. Since then, SWCNTs have been extensively used for tumor-specific imaging
and mouse organ registration (Fig. 22c–f) [28] with higher spatial resolution than
that afforded by in vivo microCT (Fig. 22g–h) [29, 31]. In mouse cerebral vasculature NIR-II imaging, SWCNTs have shown the great promising with high spatial
(<10 μm) and temporal (<200 ms per frame) resolution, at a depth of >2 mm
(Fig. 22k) [30]. This is a truly noninvasive procedure at molecular level for real-time
dynamic cerebrovascular imaging. By laser vaporization method, SWCNTs with
smaller bandgaps and larger average diameters (up to 1.24 nm) were recently
synthesized. At a depth of up to 3 mm in mouse hindlimb, SWCNTs allow in vivo
vascular NIR-II imaging with high spatial resolution up to 4 mm. Single-vesselresolved blood flow speed mapping for multiple hindlimb arterial vessels has also
been obtained simultaneously by video-rate fluorescence NIR-II imaging (Fig. 22i, j)
[32]. Moreover, in the range up to 1,700 nm, this probe may provide highperformance in vivo NIR-IIb imaging.
By creating targeted bright NIR-II emission SWCNTs, the sensitivity can be
improved for early detection. For example, a multifunctional M13 phage has been
assembled with SWCNTs via π–π interactions for use as a ligand for targeted NIR-II
imaging of tumors. Targeting M13-SWCNTs improves the uptake up to fourfold in
prostate-specific membrane antigen-positive prostate tumors compared to
nontargeted SWCNTs. In addition, it can identify sub-mm tumors that are not easily
identified by either visible or NIR-I fluorophore [86]. Other suitable targeting
strategies, such as analyte-specific receptors, have been developed for detecting
changes in NO level in response to wound-induced tissue inflammation (Fig. 22l)
[33]. In one study, SWCNTs have great promising application in NIR-II imaging
guidance for cancer resection [86]. In this research, many sub-millimeter tumor
nodules are discovered in NIR-II image-guided system compared with non-imageguided system. In addition, NIR-II imaging observes low tissue autofluorescence,
which enhances target-to-background ratios and allows detection of small tumor
nodules in confined anatomic regions. However, SWCNTs have a broad absorbance
overlap in the NIR-II region, which may cause NIR-II loss. Then, how to increase the
quantum yields will be a major focus for SWCNTs application in vivo.
112
S. He and Z. Cheng