treatment, assessment of blood supply in tissues and screening of anti-angiogenic
drugs provide new blood vessels formation, both around and within tumors. In
addition, Ag 2 S QD-based NIR-II imaging shows excellent clarity and penetration
depth for visualizing lymphatic vessels and lymph nodes during sentinel lymph node
resection than the FDA-approved, clinical standard contrast agent, ICG-based NIR-I
imaging (Fig. 18a–d) [20]. Ag 2 S QDs are also able to track and visualize mesenchymal stem cell (MSC) populations during intricate biological processes [21]. It
provides a promising method to monitor the MSCs transplantation and acquires the
important information about cell dynamics and interactions with the host central
nervous system. Furthermore, Ag 2 S QDs offer a chance for enhancing both early
disease diagnosis sensitivity and identification of lesions by targeting functional
molecules. For example, pentapeptide can bind to αVβ3 integrin receptor on tumor
cells. The pentapeptide conjugated Ag2S QDs show a significant enhancement in
sensitivity in NIR-II imaging specific tumor sites (Fig. 18f) [22].
In multimodal imaging field, QDs show a great potential application in preclinical
research. Recently, Li et al. have reported a Gd–Ag2S nanoprobe that combines
deep-tissue penetration capability of MRI with high spatiotemporal resolution of
NIR-II fluorescence imaging (Fig. 19a–c) [76]. The localization of the brain tumor
can be clearly delineated preoperatively using MRI signal generated from Gd
component in the nanoprobe, and then precise resection of the tumor can be guided
by intraoperative NIR-II fluorescence imaging produced by Ag 2 S.
Photoacoustic imaging (PAI) is an emerging optical imaging modality in which
absorbed photon energy is converted into acoustic waves that are detected using
ultrasound. PAI provides higher spatial resolution and better contrast than conventional optical imaging techniques, because ultrasound scattering in tissues is lower
by 2–3 orders of magnitude than optical scattering. A new PAI/NIR-II nanoprobe,
ICG@PEG-Ag 2 S, has recently been prepared recently [77]. This nanoprobe showed
relatively long blood retention up to 7 h and was selectively accumulated in the
region of atherosclerotic plaque due to the lipophilicity of the C18 chain to the
atherosclerosis microenvironment, and thus the atherosclerosis was monitored real
time by high contrast-enhanced PAI of ICG. Combining the high signal-to-noise
ratio (SNR) and high spatial resolution fluorescence imaging of Ag 2 S QDs in the
NIR-II, the feasibility of this new nanoprobe for atherosclerosis targeting is
achieved. Such a simple, multifunctional nanoprobe for targeting and PAI of atherosclerosis will have a great potential for future clinical applications. Ag 2 S QDs are
not only used for NR-II fluorescence imaging but also in therapy. For example,
hollow nanocage multifunctional Ag 2 S nanodots are synthesized by precisely controlled crystal growth in the presence of human serum albumin [78]. Ag 2 S nanodots
exhibit size-dependent temperature elevations and have high photothermal conversion efficiencies of 33.7–35.0%, which are comparable with those of most other
photothermal nanoparticles, such as Au nanorods (up to 22.8%) and ICG-loaded
micelles (up to 25.2%). In drug delivery, Ag 2 S QDs also demonstrate perfect drug
release under NIR-II excitation. For example, a smart Ag 2 S QDs nanoplatform
(DOX@PEG-Ag 2 S) has been obtained by loading the anticancer drug into polyethylene glycol functionalization Ag 2 S QDs (PEG-Ag 2 S QDs). The Ag 2 S QDs had up
Advancements of Second Near-Infrared Biological Window Fluorophores:. . .
107
drugs provide new blood vessels formation, both around and within tumors. In
addition, Ag 2 S QD-based NIR-II imaging shows excellent clarity and penetration
depth for visualizing lymphatic vessels and lymph nodes during sentinel lymph node
resection than the FDA-approved, clinical standard contrast agent, ICG-based NIR-I
imaging (Fig. 18a–d) [20]. Ag 2 S QDs are also able to track and visualize mesenchymal stem cell (MSC) populations during intricate biological processes [21]. It
provides a promising method to monitor the MSCs transplantation and acquires the
important information about cell dynamics and interactions with the host central
nervous system. Furthermore, Ag 2 S QDs offer a chance for enhancing both early
disease diagnosis sensitivity and identification of lesions by targeting functional
molecules. For example, pentapeptide can bind to αVβ3 integrin receptor on tumor
cells. The pentapeptide conjugated Ag2S QDs show a significant enhancement in
sensitivity in NIR-II imaging specific tumor sites (Fig. 18f) [22].
In multimodal imaging field, QDs show a great potential application in preclinical
research. Recently, Li et al. have reported a Gd–Ag2S nanoprobe that combines
deep-tissue penetration capability of MRI with high spatiotemporal resolution of
NIR-II fluorescence imaging (Fig. 19a–c) [76]. The localization of the brain tumor
can be clearly delineated preoperatively using MRI signal generated from Gd
component in the nanoprobe, and then precise resection of the tumor can be guided
by intraoperative NIR-II fluorescence imaging produced by Ag 2 S.
Photoacoustic imaging (PAI) is an emerging optical imaging modality in which
absorbed photon energy is converted into acoustic waves that are detected using
ultrasound. PAI provides higher spatial resolution and better contrast than conventional optical imaging techniques, because ultrasound scattering in tissues is lower
by 2–3 orders of magnitude than optical scattering. A new PAI/NIR-II nanoprobe,
ICG@PEG-Ag 2 S, has recently been prepared recently [77]. This nanoprobe showed
relatively long blood retention up to 7 h and was selectively accumulated in the
region of atherosclerotic plaque due to the lipophilicity of the C18 chain to the
atherosclerosis microenvironment, and thus the atherosclerosis was monitored real
time by high contrast-enhanced PAI of ICG. Combining the high signal-to-noise
ratio (SNR) and high spatial resolution fluorescence imaging of Ag 2 S QDs in the
NIR-II, the feasibility of this new nanoprobe for atherosclerosis targeting is
achieved. Such a simple, multifunctional nanoprobe for targeting and PAI of atherosclerosis will have a great potential for future clinical applications. Ag 2 S QDs are
not only used for NR-II fluorescence imaging but also in therapy. For example,
hollow nanocage multifunctional Ag 2 S nanodots are synthesized by precisely controlled crystal growth in the presence of human serum albumin [78]. Ag 2 S nanodots
exhibit size-dependent temperature elevations and have high photothermal conversion efficiencies of 33.7–35.0%, which are comparable with those of most other
photothermal nanoparticles, such as Au nanorods (up to 22.8%) and ICG-loaded
micelles (up to 25.2%). In drug delivery, Ag 2 S QDs also demonstrate perfect drug
release under NIR-II excitation. For example, a smart Ag 2 S QDs nanoplatform
(DOX@PEG-Ag 2 S) has been obtained by loading the anticancer drug into polyethylene glycol functionalization Ag 2 S QDs (PEG-Ag 2 S QDs). The Ag 2 S QDs had up
Advancements of Second Near-Infrared Biological Window Fluorophores:. . .
107