carriers needed for enhancing the delivery of radionuclides, as well as therapeutic
agents to the tumor sites, thus enhancing imaging and therapeutic efficacy.
Inorganic NPs, more specifically, offer unique sizes, high surface-to-volume ratio
and physiochemical properties that allow the conjugation of several therapeutic and
diagnostic agents, including radiotracers, through distinct synthetic strategies. Their
controllably designed surface chemistry can also enhance its targeting to disease
sites using a wide variety of probes as well as its tailorability to be adapted for
multipurpose applications.
Indubitably, the radiotracer plays a major role in the success of diagnostic
accuracy optimization. An ideal nanosystem must have no toxicity, be targeted with
optimal selectivity and specifically accumulate in the desired tissue with a high
signal-to-noise ratio, must have improved in vivo pharmacokinetics with negligible
accumulation in the RES organs and rapid and complete clearance from the body.
For that, the selection of both the isotope and the targeted carrier are of major
importance. In addition to a large amount of types of NPs being employed for this
purpose, a wide range of radioisotopes and labeling methods have also been
developed. Although, in the early years of development of molecular imaging
agents using NPs, SPECT radioisotopes, such as
99m Tc, seemed to be the choice of
a majority of the reports, this pattern is rapidly changing due to a larger availability
of PET isotopes and established radiolabeling procedures, which coordinates with
the tendency, of migrating to PET in the clinical settings, because of its superior
sensitivity and resolution of PET when compared to SPECT technique. Despite the
advances in the last decades, clinical translation of NP-based systems is still
challenging, especially due to the intrinsic heterogeneity of human tumors, both
genetically and phenotypically, as well as the fact that intra-tumoral distribution of
NPs is influenced by several different factors such as interstitial fluid pressure,
blood flow, diffusion and stroma thickness, which leads to variable and unpredictable tumor permeability. Thus, efforts from the scientific community, as well as
funding and regulatory authorities, must be undertaken to harness the full potential
of nanotheranostic moieties in the clinical settings.
Acknowledgements This work was supported, in part, by the University of Wisconsin —
Madison, the National Institutes of Health (NIBIB/NCI 1R01CA169365, 1R01EB021336,
P30CA014520), the American Cancer Society (125246-RSG-13-099-01-CCE) and CNPq
(Brazilian National Council for Scientific and Technological Development).
References
1. S. Same, A. Aghanejad, S. Akbari Nakhjavani, J. Barar, Y. Omidi, Radiolabeled
theranostics: magnetic and gold nanoparticles. Bioimpacts 6, 169–181 (2016)
2. G. Ting, C.H. Chang, H.E. Wang, T.W. Lee, Nanotargeted radionuclides for cancer nuclear
imaging and internal radiotherapy. J. Biomed. Biotechnol. (2010)
3. S.M. Moghimi, A.C. Hunter, J.C. Murray, Nanomedicine: current status and future
prospects. FASEB J. 19, 311–330 (2005)
2 Exogenous Radionanomedicine: Inorganic Nanomaterials
37
agents to the tumor sites, thus enhancing imaging and therapeutic efficacy.
Inorganic NPs, more specifically, offer unique sizes, high surface-to-volume ratio
and physiochemical properties that allow the conjugation of several therapeutic and
diagnostic agents, including radiotracers, through distinct synthetic strategies. Their
controllably designed surface chemistry can also enhance its targeting to disease
sites using a wide variety of probes as well as its tailorability to be adapted for
multipurpose applications.
Indubitably, the radiotracer plays a major role in the success of diagnostic
accuracy optimization. An ideal nanosystem must have no toxicity, be targeted with
optimal selectivity and specifically accumulate in the desired tissue with a high
signal-to-noise ratio, must have improved in vivo pharmacokinetics with negligible
accumulation in the RES organs and rapid and complete clearance from the body.
For that, the selection of both the isotope and the targeted carrier are of major
importance. In addition to a large amount of types of NPs being employed for this
purpose, a wide range of radioisotopes and labeling methods have also been
developed. Although, in the early years of development of molecular imaging
agents using NPs, SPECT radioisotopes, such as
99m Tc, seemed to be the choice of
a majority of the reports, this pattern is rapidly changing due to a larger availability
of PET isotopes and established radiolabeling procedures, which coordinates with
the tendency, of migrating to PET in the clinical settings, because of its superior
sensitivity and resolution of PET when compared to SPECT technique. Despite the
advances in the last decades, clinical translation of NP-based systems is still
challenging, especially due to the intrinsic heterogeneity of human tumors, both
genetically and phenotypically, as well as the fact that intra-tumoral distribution of
NPs is influenced by several different factors such as interstitial fluid pressure,
blood flow, diffusion and stroma thickness, which leads to variable and unpredictable tumor permeability. Thus, efforts from the scientific community, as well as
funding and regulatory authorities, must be undertaken to harness the full potential
of nanotheranostic moieties in the clinical settings.
Acknowledgements This work was supported, in part, by the University of Wisconsin —
Madison, the National Institutes of Health (NIBIB/NCI 1R01CA169365, 1R01EB021336,
P30CA014520), the American Cancer Society (125246-RSG-13-099-01-CCE) and CNPq
(Brazilian National Council for Scientific and Technological Development).
References
1. S. Same, A. Aghanejad, S. Akbari Nakhjavani, J. Barar, Y. Omidi, Radiolabeled
theranostics: magnetic and gold nanoparticles. Bioimpacts 6, 169–181 (2016)
2. G. Ting, C.H. Chang, H.E. Wang, T.W. Lee, Nanotargeted radionuclides for cancer nuclear
imaging and internal radiotherapy. J. Biomed. Biotechnol. (2010)
3. S.M. Moghimi, A.C. Hunter, J.C. Murray, Nanomedicine: current status and future
prospects. FASEB J. 19, 311–330 (2005)
2 Exogenous Radionanomedicine: Inorganic Nanomaterials
37