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Blom, Elisabeth
Publications (8 of 8) Show all publications
Blom, E., Velikyan, I., Monazzam, A., Razifar, P., Nair, M., Razifar, P., . . . Långström, B. (2011). Synthesis and characterization of scVEGF-PEG-[68Ga]NOTA and scVEGF-PEG-[68Ga]DOTA PET tracers. Journal of labelled compounds & radiopharmaceuticals, 54(11), 685-692
Open this publication in new window or tab >>Synthesis and characterization of scVEGF-PEG-[68Ga]NOTA and scVEGF-PEG-[68Ga]DOTA PET tracers
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2011 (English)In: Journal of labelled compounds & radiopharmaceuticals, ISSN 0362-4803, E-ISSN 1099-1344, Vol. 54, no 11, p. 685-692Article in journal (Refereed) Published
Abstract [en]

Vascular endothelial growth factor (VEGF) signaling via vascular endothelial growth factor receptor 2 (VEGFR-2) on tumor endothelial cells is a critical driver of tumor angiogenesis. Novel anti-angiogenic drugs target VEGF/VEGFR-2 signaling and induce changes in VEGFR-2 prevalence. To monitor VEGFR-2 prevalence in the course of treatment, we are evaluating (68)Ga positron emission tomography imaging agents based on macrocyclic chelators, site-specifically conjugated via polyethylene glycol (PEG) linkers to engineered VEGFR-2 ligand, single-chain (sc) VEGF. The (68)Ga-labeling was performed at room temperature with NOTA (2,2', 2 ''-(1,4,7-triazonane-1,4,7-triyl) triacetic acid) conjugates or at 90 degrees C by using either conventional or microwave heating with NOTA and DOTA (2,2', 2 '', 2'''-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl) tetraacetic acid) conjugates. The fastest (similar to 2min) and the highest incorporation (>90%) of (68)Ga into conjugate that resulted in the highest specific radioactivity (similar to 400MBq/nmol) was obtained with microwave heating of the conjugates. The bioactivity of the NOTA-and DOTA-containing tracers was validated in 3-D tissue culture model of 293/KDR cells engineered to express high levels of VEGFR-2. The NOTA-containing tracer also displayed a rapid accumulation (similar to 20s after intravenous injection) to steady-state level in xenograft tumor models. A combination of high specific radioactivity and maintenance of functional activity suggests that scVEGF-PEG-[(68)Ga] NOTA and scVEGF-PEG-[(68)Ga] DOTA might be promising tracers for monitoring VEGFR-2 prevalence and should be further explored.

Keywords
scVEGF, (68)Ga, radiolabeling, angiogenesis, VEGFR-2, PET
National Category
Organic Chemistry Medical Image Processing
Identifiers
urn:nbn:se:uu:diva-108589 (URN)10.1002/jlcr.1909 (DOI)000297987200001 ()
Available from: 2009-10-10 Created: 2009-09-23 Last updated: 2017-12-13Bibliographically approved
Blom, E., Itsenko, O. & Långström, B. (2011). Synthesis of 18F-labeled biotin analogues. Journal of labelled compounds & radiopharmaceuticals, 54(10), 681-683
Open this publication in new window or tab >>Synthesis of 18F-labeled biotin analogues
2011 (English)In: Journal of labelled compounds & radiopharmaceuticals, ISSN 0362-4803, E-ISSN 1099-1344, Vol. 54, no 10, p. 681-683Article in journal (Refereed) Published
Abstract [en]

A one-step 18F-labeling strategy was used to prepare three labeled analogues of the vitamin biotin, which can be a useful tracer because of its high affinity for avidin. The labeled compounds were obtained in decay-corrected yields of up to 35%, and specific radioactivity of 320 ± 60 GBq/mmol. When evaluated in situ, the analogues showed good affinity for avidin: 60–75% of the radiolabeled compounds were bound to avidin within 5 min. The binding was site-specific, as shown by blocking experiments with native biotin.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-108584 (URN)10.1002/jlcr.1913 (DOI)000295901500017 ()
Available from: 2009-10-12 Created: 2009-09-23 Last updated: 2017-12-12Bibliographically approved
Blom, E., Långström, B. & Velikyan, I. (2009). 68Ga-Labeling of Biotin Analogues and their Characterization. Bioconjugate chemistry, 20(6), 1146-1151
Open this publication in new window or tab >>68Ga-Labeling of Biotin Analogues and their Characterization
2009 (English)In: Bioconjugate chemistry, ISSN 1043-1802, E-ISSN 1520-4812, Vol. 20, no 6, p. 1146-1151Article in journal (Refereed) Published
Abstract [en]

Biotin- and Ga-68-based tracers have been suggested as tools that could be used to monitor the survival of avidin-coated islets of Langerhans isolated from pancreas and used in transplantation, i.e., to liver. Three biotin analogues with various alkyl and poly(ethylene glycol) (PEG) chains coupled to DOTA were synthesized and labeled with Ga-68. The Ga-68 labeling was studied at room temperature as well as elevated temperature using either conventional or microwave heating. Radioactivity incorporation reached 95% within 5 and 2 min using the, respectively, conventional and microwave heating modes. The specific activity of the tracers was improved by preconcentration and purification of the generator eluate. The binding of the labeled and nonlabeled conjugates to avidin in solution was compared to the binding of native biotim. All compounds maintained good affinity for avidin, though introducing the linkers and chelator, especially the PEG-groups, somewhat decreased the binding affinity. The extent of binding of the labeled compounds to avidin was 54-91% after 5 min. Blocking experiments were performed confirming the specificity of the binding of biotin analogues to avidin. The stability of the three labeled compounds in human serum was studied. The stability of the biotin analogue 8 (65% within 30 min) and avidin-biotin complex (80% within 120 min) might be sufficient for the monitoring of the islets of Langerhans. The tracers will be evaluated in in vitro experiments of avidin-coated islets of Langerhans and in transplantation models in vivo.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-106715 (URN)10.1021/bc800538s (DOI)000267117600008 ()19453100 (PubMedID)
Available from: 2009-09-24 Created: 2009-06-29 Last updated: 2017-12-13Bibliographically approved
Blom, E. (2009). Development of 18F- and 68Ga-Labelled Tracers: Design Perspectives and the Search for Faster Synthesis. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Development of 18F- and 68Ga-Labelled Tracers: Design Perspectives and the Search for Faster Synthesis
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with the design of 18F- and 68Ga-labelled positron emission tomography (PET) tracers and the development of technologies that enable faster and simpler preparation with high specific radioactivity. Techniques like microwave heating and reducing the concentrations of the precursor were investigated with this perspective. A few applications were explored using molecular design perspectives.

A nucleophilic 18F-labelling strategy using perfluoro-containing leaving groups was explored. We observed that [18F]fluoride was interacting with the perfluoro alkyl chains of the substrate, preventing the nucleophilic substitution from taking place. When a perfluoroaryl group was instead used in the leaving group, the substitution took place and purification by fluorous solid-phase extraction was possible.

18F-Labelled analogues of the monoamine oxidase-A inhibitor harmine were prepared by one-step nucleophilic fluorinations and evaluated by in vitro autoradiography, showing high specific binding.

Biotin analogues labelled with 18F and 68Ga were prepared and their binding to avidin evaluated. All analogues retained their binding ability and will be further evaluated in transplantation models with avidin-coated islets of Langerhans.

Peptide design perspectives were used in some examples where the Arg-Gly-Asp (RGD) sequence and a single-chain version of vascular endothelial growth factor (VEGF) protein functionalized with 2,2',2'',2'''-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid (DOTA) or 2,2',2''-(1,4,7-triazonane-1,4,7-triyl)triacetic acid (NOTA) as chelators were labelled with 68Ga. The RGD motif and VEGF have high affinity for, respectively, αvβ3 integrin and VEGFR-2 receptor that are overexpressed in angiogenesis process. The 68Ga-labelled scVEGF maintained its functional activity in vitro.

A polypeptide conjugate containing phosphocholine, which has affinity for the C-reactive protein released during the inflammatory process, was labelled with 68Ga for the development of an imaging agent for inflammation in vivo.

Finally [18F]/19F exchange in fluorine-containing compounds was studied in order to investigate whether the exchange reaction can be of practical use for labelling.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. p. 48
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 678
Keywords
PET, nucleophilic 18F-fluorination, perfluoro, F-SPE, molecular design, 68Ga, chelators, DOTA, NOTA, microwave, halogen exchange, harmine, biotin, RGD, VEGF, CRP
National Category
Chemical Sciences
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-108629 (URN)978-91-554-7626-7 (ISBN)
Public defence
2009-11-26, C8:305, BMC, Husargatan 3, 751 23 Uppsala, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2009-11-05 Created: 2009-09-24 Last updated: 2011-03-03Bibliographically approved
Blom, E., Karimi, F. & Långström, B. (2009). [F-18]/F-19 exchange in fluorine containing compounds for potential use in F-18-labelling strategies. Journal of labelled compounds & radiopharmaceuticals, 52(12), 504-511
Open this publication in new window or tab >>[F-18]/F-19 exchange in fluorine containing compounds for potential use in F-18-labelling strategies
2009 (English)In: Journal of labelled compounds & radiopharmaceuticals, ISSN 0362-4803, E-ISSN 1099-1344, Vol. 52, no 12, p. 504-511Article in journal (Refereed) Published
Abstract [en]

Exchange of [F-18]fluoride with F-19 in various organofluorine compounds in concentrations ranging from 0.06 to 56 mM was explored. We aimed to explore whether exchange reactions can be a potential useful labelling strategy, when there are no requirement of high specific radioactivity. Parameters such as solvents, temperature, conventional vs microwave heating, and the degree of fluorine load in some aromatic and alkyl compounds were investigated with regard to radiochemical yield and specific radioactivity. A series of fluorobenzophenones (1-6), 1-(4-fluorophenyl)ethanone (7), various activated and deactivated fluoro benzenes (8-16), N-(pentafluorophenyl)benzamide (17), (pentafluorophenyl)formamide (18), (tridecafluorohexyl) benzene (19) and tetradecafluorohexane (20) were subjected to [F-18]/F-19 exchange. To test this strategy to label biologically active molecules containing fluorine atoms in an aryl group, two analogues of WAY-100635 (21-22), Lapatinib (23), 2,5,6,7,8-pentafluoro-3-methyinaphthoquinone (24) and 1-(2,4-difluorophenyl)-3-(4-fluorophenyl)propan-l-one (25) were investigated. The multi-fluorinated molecules containing an electron-withdrawing group were successfully labelled at room temperature, whereas the monofluorinated, as well as those containing an electron-donating group, required heating for the exchange reaction to take place.

Keywords
nucleophilic 18F-fluorination, halogen exchange, organofluorine compounds, perfluoro compounds
National Category
Other Basic Medicine
Identifiers
urn:nbn:se:uu:diva-107278 (URN)10.1002/jlcr.1670 (DOI)000272471500011 ()
Available from: 2009-10-09 Created: 2009-08-03 Last updated: 2018-01-13Bibliographically approved
Blom, E., Karimi, F., Eriksson, O., Hall, H. & Långström, B. (2008). Synthesis and in vitro evaluation of 18F-β-carboline alkaloids as PET ligands. Journal of labelled compounds & radiopharmaceuticals, 51(6), 277-282
Open this publication in new window or tab >>Synthesis and in vitro evaluation of 18F-β-carboline alkaloids as PET ligands
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2008 (English)In: Journal of labelled compounds & radiopharmaceuticals, ISSN 0362-4803, E-ISSN 1099-1344, Vol. 51, no 6, p. 277-282Article in journal (Refereed) Published
Abstract [en]

A one-step 18F-labelling strategy was used to prepare four 18F-labelled analogues of 7-methoxy-1-methyl-9H-β-carboline (harmine): 7-(2-[18F]fluoroethoxy)-1-methyl-9H-β-carboline (5), 7-(3-[18F]fluoro-propoxy)-1-methyl-9H-β-carboline (6), 7-[2-(2-[18F]fluoroethoxy)ethoxy]-1-methyl-9H-β-carboline (7), and 7-{2-[2-(2-[18F]fluoroethoxy)ethoxy]-ethoxy}-1-methyl-9H-β-carboline (8). These were synthesized as potential PET ligands for monoamine oxidase A. A solution of pure labelled compound in buffer was obtained in < 70 min from end of radionuclide production, with a decay-corrected yield of up to 23%. The average specific binding to MAO-A in rat brain, determined by autoradiography experiments, was highest for compounds 7 and 8 (89 ± 2 and 96 ± 1% respectively), which was obtained at < 1 nM radioligand concentration.

Keywords
Harmine anologues, nucleophilic 18F-fluorination, one-step labelling, b-carboline alkaloids, MAO-A
National Category
Other Basic Medicine
Identifiers
urn:nbn:se:uu:diva-106708 (URN)10.1002/jlcr.1519 (DOI)000257341900032 ()
Available from: 2009-09-24 Created: 2009-06-29 Last updated: 2018-01-13Bibliographically approved
Blom, E., Velikyan, I. & Långström, B.68Ga-Labelling of RGD peptides.
Open this publication in new window or tab >>68Ga-Labelling of RGD peptides
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Several peptides comprising Arg-Gly-Asp (RGD) domain and macrocyclic chelator were labelled with 68Ga for the imaging of angiogenesis. The analogues varied in peptide constitution, linker and chelator type. The labelling efficiency did not vary with the peptide constitution and linker type, but depended on the chelator type. Four of the compounds containing 2,2',2'',2'''-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid (DOTA) chelator were labelled at 90 ± 5 °C using conventional or microwave heating reaching 90% of 68Ga incorporation after 5 and 2 min respectively, when the concentration of the precursor was 2.5 mM. The compound having 2,2',2''-(1,4,7-triazonane-1,4,7-triyl)triacetic acid (NOTA) as the chelator could be labelled at room temperature within 5 min using 2.5 mM peptide precursor. Two of the compounds contained a poly(ethylene glycol) (PEG) linker to the chelator.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-108588 (URN)
Available from: 2009-10-12 Created: 2009-09-23 Last updated: 2010-01-14
Ramapanicker, R., Blom, E., Långström, B. & Baltzer, L.Labelling of a polypeptide conjugate binder for the C-reactive protein with 68Ga for PET imaging.
Open this publication in new window or tab >>Labelling of a polypeptide conjugate binder for the C-reactive protein with 68Ga for PET imaging
(English)Manuscript (preprint) (Other academic)
Abstract [en]

A polypeptide conjugate that binds the C-reactive protein (CRP) with high affinity and specificity in human serum has been labelled with the short-lived radionuclide 68Ga (t1/2 = 68 min) for PET imaging. The binder molecule was formed by conjugating phosphocholine to the side chain of a lysine residue of a 42-residue designed polypeptide via an aliphatic spacer. For radiolabelling, a DOTA group was covalently attached to the polypeptide via a PEG spacer linked to the side chain of a Cys residue. The affinity of the binder for CRP is due to the interactions between CRP and the phosphocholine group as well as between CRP and the polypeptide scaffold itself. The affinity for CRP of the polypeptide conjugate was not affected by the incorporation of the DOTA and the dissociation constant was shown by fluorescence titration to be in the low nM range. Life times of polypeptide conjugates in human serum have been shown to depend on the level of incorporation of residues that are not recognized by proteases and thus to be tunable by design. The apparent half life of the polypeptide scaffold without conjugated groups was 10–20 min at 37 °C in human serum whereas the half-life of the labelled CRP binder was more than 24 h under the same conditions. The molecular versatility of peptides and peptide conjugates has therefore been shown to make them excellent carriers of multiple functions for in vivo applications, as illustrated here by the combination of molecular recognition with short-lived radioisotopes for PET imaging.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-108591 (URN)
Available from: 2009-10-12 Created: 2009-09-23 Last updated: 2010-01-14
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