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A possible mechanism for trapping 99mTc-HL91 in hypoxic tumor
628
Abstracts
cell lines and athymic nude mice bearing KB tumors. Results: 99mTc-1 and 99mTc-2 exhibited high specific FR binding in vitro. Both 99mTc-1 and 99mTc-2 displayed high tumor uptake (8.55 ± 2.78% ID/g and 9.77 ± 1.54% ID/g at 1 h p.i., respectively) and rapid clearance from non-target organs. Micro-SPECT/CT imaging studies in KB tumor models showed that the tumor could be clearly visualized at 4 h p.i. Conclusion: The hydrophilic linkers exhibited a profound effect on the tumor uptake and pharmacokinetic properties of the radiotracers. The two 99mTc-labeled Pteroyl-lys derivatives are very promising SPECT radiotracers to detect the FR-positive tumors. Acknowledgments This work was supported by the National Natural Science Foundation of China (20701004, 81201120).
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.043
56 Single-domain antibodies: Next-generation targeting vectors for molecular imaging Kristof Zarschlera, Katja Zscheppanga,c, Franz Kappluscha, Nils Cordesb,c, Holger Stephana
Introduction: Selective trapping mechanism for 99mTc-HL91, a hypoxia imaging agent, is still not well-defined. Previously, Brauers et al. [Eur J Nucl Med, 24 (1997), p. 943] proposed that 99mTc-HL91 can adopt either TcO-BnAO or TcO2-BnAO form in solution. We hypothesize that interconversion between these two forms may be important for hypoxic cell uptake of 99mTc-HL91 [Theor Chem Acc 2008;121: 271–278]. We test this hypothesis by HPLC under different conditions in solution. Methods: The radiolabeling and HPLC analysis of 99mTc-HL91 were carried out by direct labeling or via glucoheptonate ligand-exchange procedure. Results: 99mTc-HL91 adopted a di-oxo form, 99mTcO2-BnAO, which was stable in vitro and in vivo. Radio-HPLC profiles showed an interconversion between 99mTcO-BnAO and 99mTcO2-BnAO. When a reducing agent, SnCl2, was added into a 99mTcO2-BnAO solution under hypoxic condition (CO2 + N2 atmosphere), 99mTc-colloid (N10%) was formed. This observation suggests that a similar process may occur in hypoxic tumor cell. Conclusions: After entering into tumor cells, 99mTc(V)O2-BnAO is possibly reduced to an unstable 99mTc(IV)O-BnAO species, of which the formation of 99mTcO2 could be induced and subsequently Tc(IV)colloid was irreversibly trapped within the hypoxic cells. Results support the hypothesis that interconversion between 99mTcO-BnAO and 99mTcO2-BnAO may be a crucial mechanism responsible for trapping of 99mTc-HL91 in hypoxic tumor. http://dx.doi.org/10.1016/j.nucmedbio.2014.05.025
a
Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany b Institute of Radiooncology, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany c OncoRay – National Center for Radiation Research in Oncology, Medizinische Fakultät and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany Single-domain antibodies (sdAbs) provide significant benefits over conventional antibodies and fragments thereof in terms of size, stability, solubility as well as tumour uptake and blood clearance. Thus, sdAbs have been identified as valuable next-generation targeting moieties for molecular imaging and drug delivery in the past years. Since these probes are much less complex than conventional antibody fragments, bacterial expression represents a facile method for production of sdAbs in large amounts as soluble and functional proteins. Herein we report on heterologous high-yield expression of substantial amounts of soluble and functional sdAbs, which have an antagonistic effect on their molecular target, the epidermal growth factor receptor (EGFR). Upon radiolabeling with Tc-99m using the tricarbonyl method, we evaluated binding specificity and affinity to human EGFRexpressing tumor cells. Furthermore, we describe bioconjugation of sdAbs to fluorescent nanoparticles and characterization of sdAbnanoparticles conjugates covering in vitro cancer cell imaging, cell proliferation as well as EGFR phosphorylation and signaling. The herein highlighted valuable properties of radiolabeled sdAbs combined with tailored effector functions may result in innovative next-generation theranostics.
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.015
57 A possible mechanism for trapping 99mTc-HL91 in hypoxic tumor Lin Zhua, Wenbo Fanb, Yan Zhanga, Jinping Qiaoa a
College of Chemistry, Beijing Normal Univ., China The First Affiliated Hospital of Xiamen Univ., China
b
58 The preparation and preclinical evaluation of 99mTc-labeled microbubbles for bimodal ultrasound and SPECT imaging Aimen Zlitni, Afaf R. Genady, Nancy Janzen, John F. Valliant Department of Chemistry and Chemical Biology, McMaster University, Hamilton, ON, Canada
Because of its low cost and portability, ultrasound (US) imaging is seeing rapid growth compared to other modalities. The ability to link targeting ligands to the surface of US contrast agents, which include microbubbles (MBs), has further expanded the utility of US imaging to include molecular imaging applications. Quantitative evaluation of new targeted ultrasound agents however remains a major challenge. The aim of the work to be presented is the development of a convenient and versatile platform for the preparation and purification of targeted and technetium labeled MBs. The ability to tag MBs with 99mTc makes it possible to perform quantitative biodistribution studies on new US contrast agents and combine US imaging with single photon emission computed tomography (SPECT). Radiolabeled MBs were prepared by ligating 99m Tc-labeled biotinamido-propyl(dipicolyl)amine (99mTc-L1) to the surface of streptavidin coated MBs. These radiolabeled MBs were targeted using two different strategies. The first involves directly attaching a biotinylated derivative of the targeting vector to the surface of the MBs. The second is through a pretargeting strategy that takes advantage of a selective bioorthogonal reaction between trans-cyclooctene (TCO) and tetrazine. In this approach, a TCO-antibody derivative is allowed to bind to the site of interest prior to administering tetrazine coated (99mTc)-MBs. The preparation, purification and biological evaluation of the radiolabeled and targeted MBs will be presented.
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.099
Abstracts
cell lines and athymic nude mice bearing KB tumors. Results: 99mTc-1 and 99mTc-2 exhibited high specific FR binding in vitro. Both 99mTc-1 and 99mTc-2 displayed high tumor uptake (8.55 ± 2.78% ID/g and 9.77 ± 1.54% ID/g at 1 h p.i., respectively) and rapid clearance from non-target organs. Micro-SPECT/CT imaging studies in KB tumor models showed that the tumor could be clearly visualized at 4 h p.i. Conclusion: The hydrophilic linkers exhibited a profound effect on the tumor uptake and pharmacokinetic properties of the radiotracers. The two 99mTc-labeled Pteroyl-lys derivatives are very promising SPECT radiotracers to detect the FR-positive tumors. Acknowledgments This work was supported by the National Natural Science Foundation of China (20701004, 81201120).
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.043
56 Single-domain antibodies: Next-generation targeting vectors for molecular imaging Kristof Zarschlera, Katja Zscheppanga,c, Franz Kappluscha, Nils Cordesb,c, Holger Stephana
Introduction: Selective trapping mechanism for 99mTc-HL91, a hypoxia imaging agent, is still not well-defined. Previously, Brauers et al. [Eur J Nucl Med, 24 (1997), p. 943] proposed that 99mTc-HL91 can adopt either TcO-BnAO or TcO2-BnAO form in solution. We hypothesize that interconversion between these two forms may be important for hypoxic cell uptake of 99mTc-HL91 [Theor Chem Acc 2008;121: 271–278]. We test this hypothesis by HPLC under different conditions in solution. Methods: The radiolabeling and HPLC analysis of 99mTc-HL91 were carried out by direct labeling or via glucoheptonate ligand-exchange procedure. Results: 99mTc-HL91 adopted a di-oxo form, 99mTcO2-BnAO, which was stable in vitro and in vivo. Radio-HPLC profiles showed an interconversion between 99mTcO-BnAO and 99mTcO2-BnAO. When a reducing agent, SnCl2, was added into a 99mTcO2-BnAO solution under hypoxic condition (CO2 + N2 atmosphere), 99mTc-colloid (N10%) was formed. This observation suggests that a similar process may occur in hypoxic tumor cell. Conclusions: After entering into tumor cells, 99mTc(V)O2-BnAO is possibly reduced to an unstable 99mTc(IV)O-BnAO species, of which the formation of 99mTcO2 could be induced and subsequently Tc(IV)colloid was irreversibly trapped within the hypoxic cells. Results support the hypothesis that interconversion between 99mTcO-BnAO and 99mTcO2-BnAO may be a crucial mechanism responsible for trapping of 99mTc-HL91 in hypoxic tumor. http://dx.doi.org/10.1016/j.nucmedbio.2014.05.025
a
Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany b Institute of Radiooncology, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany c OncoRay – National Center for Radiation Research in Oncology, Medizinische Fakultät and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany Single-domain antibodies (sdAbs) provide significant benefits over conventional antibodies and fragments thereof in terms of size, stability, solubility as well as tumour uptake and blood clearance. Thus, sdAbs have been identified as valuable next-generation targeting moieties for molecular imaging and drug delivery in the past years. Since these probes are much less complex than conventional antibody fragments, bacterial expression represents a facile method for production of sdAbs in large amounts as soluble and functional proteins. Herein we report on heterologous high-yield expression of substantial amounts of soluble and functional sdAbs, which have an antagonistic effect on their molecular target, the epidermal growth factor receptor (EGFR). Upon radiolabeling with Tc-99m using the tricarbonyl method, we evaluated binding specificity and affinity to human EGFRexpressing tumor cells. Furthermore, we describe bioconjugation of sdAbs to fluorescent nanoparticles and characterization of sdAbnanoparticles conjugates covering in vitro cancer cell imaging, cell proliferation as well as EGFR phosphorylation and signaling. The herein highlighted valuable properties of radiolabeled sdAbs combined with tailored effector functions may result in innovative next-generation theranostics.
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.015
57 A possible mechanism for trapping 99mTc-HL91 in hypoxic tumor Lin Zhua, Wenbo Fanb, Yan Zhanga, Jinping Qiaoa a
College of Chemistry, Beijing Normal Univ., China The First Affiliated Hospital of Xiamen Univ., China
b
58 The preparation and preclinical evaluation of 99mTc-labeled microbubbles for bimodal ultrasound and SPECT imaging Aimen Zlitni, Afaf R. Genady, Nancy Janzen, John F. Valliant Department of Chemistry and Chemical Biology, McMaster University, Hamilton, ON, Canada
Because of its low cost and portability, ultrasound (US) imaging is seeing rapid growth compared to other modalities. The ability to link targeting ligands to the surface of US contrast agents, which include microbubbles (MBs), has further expanded the utility of US imaging to include molecular imaging applications. Quantitative evaluation of new targeted ultrasound agents however remains a major challenge. The aim of the work to be presented is the development of a convenient and versatile platform for the preparation and purification of targeted and technetium labeled MBs. The ability to tag MBs with 99mTc makes it possible to perform quantitative biodistribution studies on new US contrast agents and combine US imaging with single photon emission computed tomography (SPECT). Radiolabeled MBs were prepared by ligating 99m Tc-labeled biotinamido-propyl(dipicolyl)amine (99mTc-L1) to the surface of streptavidin coated MBs. These radiolabeled MBs were targeted using two different strategies. The first involves directly attaching a biotinylated derivative of the targeting vector to the surface of the MBs. The second is through a pretargeting strategy that takes advantage of a selective bioorthogonal reaction between trans-cyclooctene (TCO) and tetrazine. In this approach, a TCO-antibody derivative is allowed to bind to the site of interest prior to administering tetrazine coated (99mTc)-MBs. The preparation, purification and biological evaluation of the radiolabeled and targeted MBs will be presented.
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.099