Nanomaterials for Medical Imaging …
383
radionuclide for PET imaging, their short half-life of 109 min, and impedes the study
of biochemical process in the range between days and weeks. NPs can be labeled
with positrons and gamma-emitting radionuclides. In this context,
64 Cu labeled Si
QDs were developed and used for PET imaging in vivo and ex vivo gamma counting
[326]. DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) is used for
the complexation of
64 Cu ions steric hindrance leading to unstable radiolabeling.
A new approach using new bifunctional DO3A (1,4,7,10-tetraazacyclododecane1,4,7-triacetic acid) with a more flexible functional arm for chelation of
64 Cu was
implemented. This improved sterics resulted in a very much stable complex with
less loss of radiolabeling upon chelation to silicon QDs. In vivo studies demonstrated a faster clearance of Si QDs from the body through renal filtration and
urinary bladder. At the same time, some QDs with a larger hydrodynamic diameter was taken up through the reticuloendothelial system and accumulated in the
liver. Mesoporous silica NPs (MSNP) provide the advantage of offering less toxicity and ease of uptake and transport by cells. A new approach based on MSNP
was implemented for tracking neural stem cells in the brain using SPECT [327].
To synthesize the nanoparticle sol-gel co-condensation method was employed and
conjugated with DOTA-N-hydroxysuccinimide-ester for radiolabeling. The results
indicated that MSNP could be tracked as they move towards the intracranial glioma
using SPECT imaging in real-time after intracranial and systemic administration.
10 Conclusions
Overall, this chapter explains the new developments in nanoprobes used as preclinical
imaging modalities like CT, MRI, ultrasound, and optical systems. Advancements
in imaging parameters are made by the current state-of-art nanomaterials in terms of
sensitivity, biodistribution, target, and multimodal imaging ability. Nanotechnology
is transforming the imaging capabilities and increasing its growth and high performance in both clinical and preclinical imaging studies enabling them to fasten the
drug delivery process. Nanotechnology-based imaging probes provide a high surface
to volume ratio, low cost, ease of functionalization, and less toxicity compared to
other probes. The combination of drug and imaging agent with targeting ability and
its advancements in multimodal imaging capability are very much encouraging and
presented with good examples.
A particular emphasis on nanomaterials, focusing on the problems faced by
imaging agents in preclinical imaging systems have been discussed. Literature has
clearly suggested that nanomaterials with desired size and shape are important to
advance pre-clinical imaging systems and to improvise the imaging parameters.
Furthermore, nanoprobes have proved their usefulness by binding with new targets
and imaging sensitive regions compared to conventional agents. Factors that influence commercialization of nanoparticles are their in vivo toxicity. Also, the greatest
challenge of upcoming nanomaterials on retention and reactivity with proteins in the
diseased region is still questionable. It is important for the nanoscientists to work on
383
radionuclide for PET imaging, their short half-life of 109 min, and impedes the study
of biochemical process in the range between days and weeks. NPs can be labeled
with positrons and gamma-emitting radionuclides. In this context,
64 Cu labeled Si
QDs were developed and used for PET imaging in vivo and ex vivo gamma counting
[326]. DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) is used for
the complexation of
64 Cu ions steric hindrance leading to unstable radiolabeling.
A new approach using new bifunctional DO3A (1,4,7,10-tetraazacyclododecane1,4,7-triacetic acid) with a more flexible functional arm for chelation of
64 Cu was
implemented. This improved sterics resulted in a very much stable complex with
less loss of radiolabeling upon chelation to silicon QDs. In vivo studies demonstrated a faster clearance of Si QDs from the body through renal filtration and
urinary bladder. At the same time, some QDs with a larger hydrodynamic diameter was taken up through the reticuloendothelial system and accumulated in the
liver. Mesoporous silica NPs (MSNP) provide the advantage of offering less toxicity and ease of uptake and transport by cells. A new approach based on MSNP
was implemented for tracking neural stem cells in the brain using SPECT [327].
To synthesize the nanoparticle sol-gel co-condensation method was employed and
conjugated with DOTA-N-hydroxysuccinimide-ester for radiolabeling. The results
indicated that MSNP could be tracked as they move towards the intracranial glioma
using SPECT imaging in real-time after intracranial and systemic administration.
10 Conclusions
Overall, this chapter explains the new developments in nanoprobes used as preclinical
imaging modalities like CT, MRI, ultrasound, and optical systems. Advancements
in imaging parameters are made by the current state-of-art nanomaterials in terms of
sensitivity, biodistribution, target, and multimodal imaging ability. Nanotechnology
is transforming the imaging capabilities and increasing its growth and high performance in both clinical and preclinical imaging studies enabling them to fasten the
drug delivery process. Nanotechnology-based imaging probes provide a high surface
to volume ratio, low cost, ease of functionalization, and less toxicity compared to
other probes. The combination of drug and imaging agent with targeting ability and
its advancements in multimodal imaging capability are very much encouraging and
presented with good examples.
A particular emphasis on nanomaterials, focusing on the problems faced by
imaging agents in preclinical imaging systems have been discussed. Literature has
clearly suggested that nanomaterials with desired size and shape are important to
advance pre-clinical imaging systems and to improvise the imaging parameters.
Furthermore, nanoprobes have proved their usefulness by binding with new targets
and imaging sensitive regions compared to conventional agents. Factors that influence commercialization of nanoparticles are their in vivo toxicity. Also, the greatest
challenge of upcoming nanomaterials on retention and reactivity with proteins in the
diseased region is still questionable. It is important for the nanoscientists to work on