Publications by authors named "Niels Langkjaer"

17 Publications

  • Page 1 of 1

GMP production of 6-[F]Fluoro-L-DOPA for PET/CT imaging by different synthetic routes: a three center experience.

EJNMMI Radiopharm Chem 2021 Jun 12;6(1):21. Epub 2021 Jun 12.

Department of Nuclear Medicine, Copenhagen University Hospital Herlev and Gentofte, Borgmester Ib Juuls vej 31, DK-2730, Herlev, Denmark.

Background: The radiofluorinated levodopa analogue 6-[F]F-L-DOPA (3,4-dihydroxy-6-F-L-phenylalanine) is a commonly employed radiotracer for PET/CT imaging of multiple oncological and neurological indications. An unusually large number of different radiosyntheses have been published to the point where two different Ph. Eur. monographs exist depending on whether the chemistry relies on electrophilic or nucleophilic radiosubstitution of appropriate chemical precursors. For new PET imaging sites wishing to adopt [F]FDOPA into clinical practice, selecting the appropriate production process may be difficult and dependent on the clinical needs of the site.

Methods: Data from four years of [F]FDOPA production at three different clinical sites are collected and compared. These three sites, Aarhus University Hospital (AUH), Odense University Hospital (OUH), and Herlev University Hospital (HUH), produce the radiotracer by different radiosynthetic routes with AUH adopting an electrophilic strategy, while OUH and HUH employ two different nucleophilic approaches. Production failure rates, radiochemical yields, and molar activities are compared across sites and time. Additionally, the clinical use of the radiotracer over the time period considered at the different sites are presented and discussed.

Results: The electrophilic substitution route suffers from being demanding in terms of cyclotron operation and maintenance. This challenge, however, was found to be compensated by a production failure rate significantly below that of both nucleophilic approaches; a result of simpler chemistry. The five-step nucleophilic approach employed at HUH produces superior radiochemical yields compared to the three-step approach adopted at OUH but suffers from the need for more comprehensive synthesis equipment given the multi-step nature of the procedure, including HPLC purification. While the procedure at OUH furnishes the lowest radiochemical yield of the synthetic routes considered, it produces the highest molar activity. This is of importance across the clinical applications of the tracer discussed here, including dopamine synthesis in striatum of subjects with schizophrenia and congenital hyperinsulinism in infants.

Conclusion: For most sites either of the two nucleophilic substitution strategies should be favored. However, which of the two will depend on whether a given site wishes to optimize the radiochemical yield or the ease of the use.
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http://dx.doi.org/10.1186/s41181-021-00135-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8197687PMC
June 2021

Auger electron therapy of glioblastoma using [I]5-iodo-2'-deoxyuridine and concomitant chemotherapy - Evaluation of a potential treatment strategy.

Nucl Med Biol 2021 May-Jun;96-97:35-40. Epub 2021 Mar 17.

Department of Nuclear Medicine, Odense University Hospital, Odense, Denmark; Department of Clinical Research, University of Southern Denmark, Odense, Denmark. Electronic address:

Introduction: Treatment of glioblastomas (GBM) using the Auger electron emitting compound [I]5-Iodo-2'-deoxyuridine ([I]I-UdR), combined with the thymidylate synthase inhibitor methotrexate (MTX) and concomitant chemotherapy with temozolomide (TMZ) has recently shown very promising therapeutic effects in vitro and in vivo in animals. The aim of the current study was to investigate if the therapeutic effects of this multimodal treatment strategy could be further increased by the thymidylate synthase inhibitor, 5-fluoro-2'-deoxyuridine (F-UdR), in comparison to MTX, and if the co-treatment should be given in a neoadjuvant or adjuvant setting.

Methods: A patient-derived GBM cancer stem cell (CSC)-enriched cell line, grown as neurospheres, was employed to evaluate DNA-incorporation of [I]I-UdR, determined by a DNA precipitation assay, using either pre-treatment or co-treatment with MTX or F-UdR. The therapeutic effects in the CSC-enriched cell line after exposure to various combinations of MTX, F-UdR, TMZ and [I]I-UdR were also investigated by a CellTiter-Blue assay.

Results: The highest general increase in [I]I-UdR incorporation was observed with F-UdR co-treatment, which resulted in approx. 2.5-fold increase in the DNA-associated activity. Also the cell viability was significantly decreased when F-UdR was combined with [I]I-UdR compared to [I]I-UdR alone at all activity concentrations tested. MTX was redundant when combined with 400 and 500 Bq/ml [I]I-UdR. TMZ was effective in combination with either [I]I-UdR alone or with both thymidylate synthase inhibitors combined with 50-100 Bq/ml [I]I-UdR.

Conclusions: Overall, our study revealed a higher incorporation and therapeutic effect of [I]I-UdR when GBM cells were co-treated with F-UdR compared to MTX. The therapeutic effects were further increased when TMZ was combined with [I]I-UdR in combination with the thymidylate synthase inhibitors.

Advances In Knowledge And Implications For Patient Care: Auger electron therapy in combination with thymidylate synthase inhibition and concomitant chemotherapy has the potential to become a future therapeutic treatment option for patients with glioblastoma.
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http://dx.doi.org/10.1016/j.nucmedbio.2021.03.001DOI Listing
March 2021

Multi-curie production of gallium-68 on a biomedical cyclotron and automated radiolabelling of PSMA-11 and DOTATATE.

EJNMMI Radiopharm Chem 2021 Jan 7;6(1). Epub 2021 Jan 7.

Department of Nuclear Medicine, Odense University Hospital, Kløvervænget 47, 5000, Odense, Denmark.

Background: With increasing clinical demand for gallium-68, commercial germanium-68/gallium-68 ([Ge]Ge/[Ga]Ga) generators are incapable of supplying sufficient amounts of the short-lived daughter isotope. In this study, we demonstrate a high-yield, automated method for producing multi-Curie levels of [Ga]GaCl from solid zinc-68 targets and subsequent labelling to produce clinical-grade [Ga]Ga-PSMA-11 and [Ga]Ga-DOTATATE.

Results: Enriched zinc-68 targets were irradiated at up to 80 µA with 13 MeV protons for 120 min; repeatedly producing up to 194 GBq (5.24 Ci) of purified gallium-68 in the form of [Ga]GaCl at the end of purification (EOP) from an expected > 370 GBq (> 10 Ci) at end of bombardment. A fully automated dissolution/separation process was completed in 35 min. Isolated product was analysed according to the Ph. Eur. monograph for accelerator produced [Ga]GaCl and found to comply with all specifications. In every instance, the radiochemical purity exceeded 99.9% and importantly, the radionuclidic purity was sufficient to allow for a shelf-life of up to 7 h based on this metric alone. Fully automated production of up to 72.2 GBq [Ga]Ga-PSMA-11 was performed, providing a product with high radiochemical purity (> 98.2%) and very high apparent molar activities of up to 722 MBq/nmol. Further, manual radiolabelling of up to 3.2 GBq DOTATATE was performed in high yields (> 95%) and with apparent molar activities (9-25 MBq/nmol) sufficient for clinical use.

Conclusions: We have developed a high-yielding, automated method for the production of very high amounts of [Ga]GaCl, sufficient to supply proximal radiopharmacies. The reported method led to record-high purified gallium-68 activities (194 GBq at end of purification) and subsequent labelling of PSMA-11 and DOTATATE. The process was highly automated from irradiation through to formulation of the product, and as such comprised a high level of radiation protection. The quality control results obtained for both [Ga]GaCl for radiolabelling and [Ga]Ga-PSMA-11 are promising for clinical use.
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http://dx.doi.org/10.1186/s41181-020-00114-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7790954PMC
January 2021

Evaluation of somatostatin and nucleolin receptors for therapeutic delivery in non-small cell lung cancer stem cells applying the somatostatin-analog DOTATATE and the nucleolin-targeting aptamer AS1411.

PLoS One 2017 22;12(5):e0178286. Epub 2017 May 22.

Molecular Oncology, University of Southern Denmark, Odense, Denmark.

Cancer stem cells represent the putative tumor-driving subpopulation thought to account for drug resistance, relapse, and metastatic spread of epithelial and other cancer types. Accordingly, cell surface markers for therapeutic delivery to cancer stem cells are subject of intense research. Somatostatin receptor 2 and nucleolin are known to be overexpressed by various cancer types, which have elicited comprehensive efforts to explore their therapeutic utilization. Here, we evaluated somatostatin receptor 2 targeting and nucleolin targeting for therapeutic delivery to cancer stem cells from lung cancer. Nucleolin is expressed highly but not selectively, while somatostatin receptor 2 is expressed selectively but not highly by cancer cells. The non-small cell lung cancer cell lines A549 and H1299, displayed average levels of both surface molecules as judged based on analysis of a larger cell line panel. H1299 compared to A549 cells showed significantly elevated sphere-forming capacity, indicating higher cancer stem cell content, thus qualifying as suitable test system. Nucleolin-targeting 57Co-DOTA-AS1411 aptamer showed efficient internalization by cancer cells and, remarkably, at even higher efficiency by cancer stem cells. In contrast, somatostatin receptor 2 expression levels were not sufficiently high in H1299 cells to confer efficient uptake by either non-cancer stem cells or cancer stem cells. The data provides indication that the nucleolin-targeting AS1411 aptamer might be used for therapeutic delivery to non-small cell lung cancer stem cells.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0178286PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5440050PMC
September 2017

3'-Pyrene-modified unlocked nucleic acids: synthesis, fluorescence properties and a surprising stabilization effect on duplexes and triplexes.

Org Biomol Chem 2017 Mar;15(9):2073-2085

Biomolecular Nanoscale Engineering Center, Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark.

Efficient synthesis of a new 3'-O-amino-UNA monomer was developed as a scaffold for further functionalization and incorporation into oligonucleotides (ONs). Pyrene-functionalized 3'-O-amino-UNA was incorporated one, two or three times into 21-mer DNA and 2'-O-Me-RNA ONs. Duplex melting temperatures, circular dichroism (CD) spectra, steady-state fluorescence emission spectra, UV/Vis absorption spectra and triplex melting temperatures were measured for the modified duplexes. The presence of the pyrene-modified UNA monomer lead to a surprising and unprecedented thermal stabilization of especially DNA:DNA duplexes when compared to the corresponding unmodified DNA:DNA duplexes. Improved mismatch discrimination was also seen for some of the modified duplexes. CD spectra revealed no major differences between modified and unmodified duplexes. Molecular modeling showed that the pyrene moieties were located in the minor groove of DNA:DNA duplexes as confirmed by CD and UV/Vis absorption studies. Upon multiple incorporations of the monomer in single-stranded ONs, steady-state fluorescence emission studies revealed the formation of a pyrene excimer which in most cases was quenched upon duplex hybridization, and fluorescence-based detection of mismatched hybridization was observed for some modified strand constitutions. Incorporation of the monomer in a triplex-forming oligonucleotide (TFO) strand lead to an increase of triplex melting temperature both at pH 6.0 and pH 7.0 for parallel triplexes - again an effect that has not been reported earlier for UNA-containing ONs. Steady-state fluorescence emission studies revealed significant differences in fluorescence for single-stranded ONs and triplexes.
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http://dx.doi.org/10.1039/c6ob02773cDOI Listing
March 2017

Development of an Efficient G-Quadruplex-Stabilised Thrombin-Binding Aptamer Containing a Three-Carbon Spacer Molecule.

Chembiochem 2017 04 15;18(8):755-763. Epub 2017 Mar 15.

Nucleic Acid Center, Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark.

The thrombin-binding aptamer (TBA), which shows anticoagulant properties, is one of the most studied G-quadruplex-forming aptamers. In this study, we investigated the impact of different chemical modifications such as a three-carbon spacer (spacer-C ), unlocked nucleic acid (UNA) and 3'-amino-modified UNA (amino-UNA) on the structural dynamics and stability of TBA. All three modifications were incorporated at three different loop positions (T3, T7, T12) of the TBA G-quadruplex structure to result in a series of TBA variants and their stability was studied by thermal denaturation; folding was studied by circular dichroism spectroscopy and thrombin clotting time. The results showed that spacer-C introduction at the T7 loop position (TBA-SP7) significantly improved stability and thrombin clotting time while maintaining a similar binding affinity as TBA to thrombin. Detailed molecular modelling experiments provided novel insights into the experimental observations, further supporting the efficacy of TBA-SP7. The results of this study could provide valuable information for future designs of TBA analogues with superior thrombin inhibition properties.
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http://dx.doi.org/10.1002/cbic.201600654DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5413854PMC
April 2017

Highly Effective Auger-Electron Therapy in an Orthotopic Glioblastoma Xenograft Model using Convection-Enhanced Delivery.

Theranostics 2016 29;6(12):2278-2291. Epub 2016 Sep 29.

Department of Clinical Research, University of Southern Denmark, Odense, Denmark;; Department of Pathology, Odense University Hospital, Odense, Denmark.

Glioblastoma, the most common and malignant primary brain tumor, always recurs after standard treatment. Therefore, promising new therapeutic approaches are needed. Short-range Auger-electron-emitters carry the ability of causing highly damaging radiation effects in cells. The aim of this study was to test the effect of [I]5-Iodo-2'-deoxyuridine (I-UdR, a radioactive Auger-electron-emitting thymidine analogue) Auger-therapy on immature glioblastoma spheroid cultures and orthotopic xenografted glioblastoma-bearing rats, the latter by means of convection-enhanced delivery (CED). Moreover, we aimed to determine if the therapeutic effect could be enhanced when combining I-UdR therapy with the currently used first-line chemotherapeutic agent temozolomide. I-UdR significantly decreased glioblastoma cell viability and migration and the cell viability was further decreased by co-treatment with methotrexate and/or temozolomide. Intratumoral CED of methotrexate and I-UdR with and without concomitant systemic temozolomide chemotherapy significantly reduced the tumor burden in orthotopically xenografted glioblastoma-bearing nude rats. Thus, 100% (8/8) of the animals survived the entire observation period of 180 days when subjected to the combined Auger-chemotherapy while 57% (4/7) survived after the Auger-therapy alone. No animals (0/8) treated with temozolomide alone survived longer than 50 days. Blood samples and histology showed no signs of dose-limiting adverse effects. In conclusion, the multidrug approach consisting of CED of methotrexate and I-UdR with concomitant systemic temozolomide was safe and very effective leading to 100% survival in an orthotopic xenograft glioblastoma model. Therefore, this therapeutic strategy may be a promising option for future glioblastoma therapy.
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http://dx.doi.org/10.7150/thno.15898DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5135448PMC
October 2017

Watson-Crick hydrogen bonding of unlocked nucleic acids.

Bioorg Med Chem Lett 2015 Nov 20;25(22):5064-6. Epub 2015 Oct 20.

Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznań, Poland. Electronic address:

We herein describe the synthesis of two new unlocked nucleic acid building blocks containing hypoxanthine and 2,6-diaminopurine as nucleobase moieties and their incorporation into oligonucleotides. The modified oligonucleotides were used to examine the thermodynamic properties of UNA against unmodified oligonucleotides and the resulting thermodynamic data support that the hydrogen bonding face of UNA is Watson-Crick like.
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http://dx.doi.org/10.1016/j.bmcl.2015.10.024DOI Listing
November 2015

Bis-pyrene-modified unlocked nucleic acids: synthesis, hybridization studies, and fluorescent properties.

ChemMedChem 2014 Sep 18;9(9):2120-7. Epub 2014 Jul 18.

Nucleic Acid Center, Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Campusvej 55, 5230 Odense M (Denmark); Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610 Prague 6 (Czech Republic).

Efficient synthesis of a building block for the incorporation of a bis-pyrene-modified unlocked nucleic acid (UNA) into oligonucleotides (DNA*) was developed. The presence of bis-pyrene-modified UNA within a duplex leads to duplex destabilization that is more profound in DNA*/RNA and less distinct in DNA*/DNA duplexes. Nevertheless, the destabilization effect of bis-pyrene-modified UNA is weaker than that of unmodified UNA. Some oligonucleotides with bis-pyrene-modified UNA incorporations displayed superior mismatch discrimination capabilities. UV/Vis absorption and molecular modeling studies indicate that the pyrene groups of bis-pyrene-modified UNA are located in the major groove of a duplex. Oligonucleotides containing two bis-pyrene-modified UNA monomers showed low pyrene monomer emission in bulge-containing duplexes, high pyrene monomer emission in fully matched duplexes, and 5-(pyrenyl)uracil:pyrene exciplex emission in the single-stranded form. Such fluorescent properties enable the application of bis-pyrene-modified UNA in the development of fluorescence probes for DNA/RNA detection and for detection of deletions at specific positions.
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http://dx.doi.org/10.1002/cmdc.201402185DOI Listing
September 2014

Selective biocatalytic acylation studies on 5'-O-(4,4'-dimethoxytrityl)-2',3'-secouridine: an efficient synthesis of UNA monomer.

Nucleosides Nucleotides Nucleic Acids 2012 ;31(12):831-40

Bioorganic Laboratory, Department of Chemistry, University of Delhi, Delhi, India.

Lipozyme(®) TL IM (Theremomyces lanuginosus lipase immobilized on silica) in toluene catalyzes the acylation of the 2'-OH over the 3'-OH group in 5'-O-(4,4'-dimethoxytrityl)-2',3'-secouridine (5'-O-DMT-2',3'-secouridine) in a highly selective fashion in moderate to almost quantitative yields. The turn over during benzoyl transfer reactions mediated by vinyl benzoate or benzoic anhydride was faster than in acyl transfer reactions with vinyl acetate or C(1) to C(5) acid anhydrides; except in the case of butanoic anhydride. The 2'-O-benzoyl-5'-O-DMT-2',3'-secouridine obtained by Lipozyme(®) TL IM catalyzed benzoylation of 5'-O-DMT-2',3'-secouridine was successfully converted into its 3'-O-phosphoramidite derivative in satisfactory yield, which is a building block for the preparation of oligonucleotides containing the uracil monomer of UNA (unlocked nucleic acid).
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http://dx.doi.org/10.1080/15257770.2012.734424DOI Listing
January 2014

A screen of chemical modifications identifies position-specific modification by UNA to most potently reduce siRNA off-target effects.

Nucleic Acids Res 2010 Sep 7;38(17):5761-73. Epub 2010 May 7.

Department of Molecular Biology, University of Aarhus, Arhus, Nucleic Acid Center, Department of Physics and Chemistry, University of Southern Denmark, Odense, Denmark.

Small interfering RNAs (siRNAs) are now established as the preferred tool to inhibit gene function in mammalian cells yet trigger unintended gene silencing due to their inherent miRNA-like behavior. Such off-target effects are primarily mediated by the sequence-specific interaction between the siRNA seed regions (position 2-8 of either siRNA strand counting from the 5'-end) and complementary sequences in the 3'UTR of (off-) targets. It was previously shown that chemical modification of siRNAs can reduce off-targeting but only very few modifications have been tested leaving more to be identified. Here we developed a luciferase reporter-based assay suitable to monitor siRNA off-targeting in a high throughput manner using stable cell lines. We investigated the impact of chemically modifying single nucleotide positions within the siRNA seed on siRNA function and off-targeting using 10 different types of chemical modifications, three different target sequences and three siRNA concentrations. We found several differently modified siRNAs to exercise reduced off-targeting yet incorporation of the strongly destabilizing unlocked nucleic acid (UNA) modification into position 7 of the siRNA most potently reduced off-targeting for all tested sequences. Notably, such position-specific destabilization of siRNA-target interactions did not significantly reduce siRNA potency and is therefore well suited for future siRNA designs especially for applications in vivo where siRNA concentrations, expectedly, will be low.
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http://dx.doi.org/10.1093/nar/gkq341DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2943616PMC
September 2010

Synthesis and biophysical studies of coronene functionalized 2'-amino-LNA: a novel class of fluorescent nucleic acids.

Bioconjug Chem 2010 Mar 25;21(3):513-20. Epub 2010 Jan 25.

Nucleic Acid Center, Department of Physics and Chemistry, University of Southern Denmark, 5230 Odense M, Denmark.

Incorporation of 2'-N-(coronen-1-yl)methyl-2'-amino-LNA monomer X or 2'-N-4-(coronen-1-yl)-4-oxobutanoyl-2'-amino-LNA monomer Y into short DNA strands induces high binding affinity toward DNA or RNA and a marked red-shift in steady-state fluorescence emission upon hybridization to cDNA or RNA.
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http://dx.doi.org/10.1021/bc900421rDOI Listing
March 2010

UNA (unlocked nucleic acid): a flexible RNA mimic that allows engineering of nucleic acid duplex stability.

Bioorg Med Chem 2009 Aug 27;17(15):5420-5. Epub 2009 Jun 27.

Nucleic Acid Center, Department of Physics and Chemistry, University of Southern Denmark, DK-5230 Odense M, Denmark.

UNA (unlocked nucleic acid) monomers are acyclic derivatives of RNA lacking the C2'-C3'-bond of the ribose ring of RNA. Synthesis of phosphoramidite UNA building blocks of the nucleobases adenine, cytosine, guanine, and uracil is described herein together with their incorporation into RNA strands. UNA monomers additively decrease nucleic acid duplex stability and can be positioned strategically to induce either lack of discrimination of mismatches, that is, universal base behavior, or increased discrimination of mismatches, that is, improved hybridization specificity. UNA-modified RNA duplexes are shown to structurally mimic unmodified RNA duplexes by CD spectroscopy.
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http://dx.doi.org/10.1016/j.bmc.2009.06.045DOI Listing
August 2009

Filling the gap in LNA antisense oligo gapmers: the effects of unlocked nucleic acid (UNA) and 4'-C-hydroxymethyl-DNA modifications on RNase H recruitment and efficacy of an LNA gapmer.

Mol Biosyst 2009 Aug 19;5(8):838-43. Epub 2009 May 19.

Dept of Neurogenetics AMC, 1105 AZ Amsterdam, The Netherlands.

Stability against nucleases, affinity for the targeted mRNA and the ability to recruit RNase H are prerequisites for antisense oligonucleotide (AON) applications where gene expression knockdown is required. Typically chimeric gapmer AON designs are used with a central continuous stretch of RNase H recruiting nucleotides (e.g. phosphorothioate DNA), flanked by affinity and stability-enhancing modified nucleotides. However, many types of nucleotide modifications in the central DNA gap can disturb RNase H function. Here we present studies into two different types of nucleotide modifications, a flexible acyclic RNA analog named unlocked nucleic acid (UNA) and 4'-C-hydroxymethyl-DNA in the gap of an LNA (locked nucleic acid) flanked gapmer. We compared the efficacy of mRNA degradation by the gap modified LNA antisense gapmers in cell-free assays and cultured cells. This study shows that both UNA and 4'-C-hydroxymethyl-DNA gap insertions are compatible with RNase H activity when used sparingly. However, multiple 4'-C-hydroxymethyl-DNA modifications are better tolerated by RNase H than multiple UNA modifications in the gap. Furthermore, this report shows that LNA gapmer AONs with multiple 4'-C-hydroxymethyl-DNA moieties in the gap can mediate target knockdown in vivo.
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http://dx.doi.org/10.1039/b903922hDOI Listing
August 2009

A large-scale chemical modification screen identifies design rules to generate siRNAs with high activity, high stability and low toxicity.

Nucleic Acids Res 2009 May 12;37(9):2867-81. Epub 2009 Mar 12.

Department of Molecular Biology, University of Aarhus, Arhus, Nucleic Acid Center, University of Southern Denmark, Odense, Denmark.

The use of chemically synthesized short interfering RNAs (siRNAs) is currently the method of choice to manipulate gene expression in mammalian cell culture, yet improvements of siRNA design is expectably required for successful application in vivo. Several studies have aimed at improving siRNA performance through the introduction of chemical modifications but a direct comparison of these results is difficult. We have directly compared the effect of 21 types of chemical modifications on siRNA activity and toxicity in a total of 2160 siRNA duplexes. We demonstrate that siRNA activity is primarily enhanced by favouring the incorporation of the intended antisense strand during RNA-induced silencing complex (RISC) loading by modulation of siRNA thermodynamic asymmetry and engineering of siRNA 3'-overhangs. Collectively, our results provide unique insights into the tolerance for chemical modifications and provide a simple guide to successful chemical modification of siRNAs with improved activity, stability and low toxicity.
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http://dx.doi.org/10.1093/nar/gkp106DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2685080PMC
May 2009

Nucleosides with 1,4-dioxane as sugar moiety.

Nucleic Acids Symp Ser (Oxf) 2008 (52):269-70

Nucleic Acid Center, Department of Physics and Chemistry, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark.

A synthetic route towards novel nucleosides with 1,4- dioxane as the sugar moiety has been developed. The dioxane moiety features a second anomeric center, which has been phosphitylated giving a diastereomeric mixture of the corresponding phosphoramidites.
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http://dx.doi.org/10.1093/nass/nrn136DOI Listing
November 2010

Unlocked nucleic acid (UNA) and UNA derivatives: thermal denaturation studies.

Nucleic Acids Symp Ser (Oxf) 2008 (52):133-4

Nucleic Acid Center, Department of Physics and Chemistry, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark.

A study on the thermal stability of duplexes formed between unlocked nucleic acid (UNA) modified DNA and RNA oligonucleotides and complementary DNA and RNA is presented. The acyclic UNA monomers are shown to induce a decrease in duplex thermal stability.
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http://dx.doi.org/10.1093/nass/nrn068DOI Listing
November 2010
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