| 1. |
- Stenler, S., et al.
(author)
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Micro-minicircle gene therapy : Implications of size on fermentation, complexation, shearing resistance, and expression
- 2014
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In: Molecular Therapy Nucleic Acids. - : Elsevier BV. - 2162-2531. ; 3, s. e140-
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Journal article (peer-reviewed)abstract
- The minicircle (MC), composed of eukaryotic sequences only, is an interesting approach to increase the safety and efficiency of plasmid-based vectors for gene therapy. In this paper, we investigate micro-MC (miMC) vectors encoding small regulatory RNA. We use a construct encoding a splice-correcting U7 small nuclear RNA, which results in a vector of 650 base pairs (bp), as compared to a conventional 3600 bp plasmid carrying the same expression cassette. Furthermore, we construct miMCs of varying sizes carrying different number of these cassettes. This allows us to evaluate how size influences production, supercoiling, stability and efficiency of the vector. We characterize coiling morphology by atomic force microscopy and measure the resistance to shearing forces caused by an injector device, the Biojector. We compare the behavior of miMCs and plasmids in vitro using lipofection and electroporation, as well as in vivo in mice. We here show that when the size of the miMC is reduced, the formation of dimers and trimers increases. There seems to be a lower size limit for efficient expression. We demonstrate that miMCs are more robust than plasmids when exposed to shearing forces, and that they show extended expression in vivo.
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| 2. |
- Álvarez Asencio, Rubén, et al.
(author)
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Nanotribology : Tribotronics, ionic liquids and control of surface interactions
- 2013
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In: 5th World Tribology Congress, WTC 2013. ; , s. 3106-3108
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Conference paper (peer-reviewed)abstract
- The interfacial ordering of Ionic liquids leads to interesting nanotribological properties as revealed by colloid probe studies. The first of these is the clear correlation between the number of ion pairs trapped in the tribological contact and the friction coefficient displayed. The second is the fact that the surface electrical potential can be used to control the composition of the boundary layer and thus tune the friction. Thirdly, the interfacial ordering appears to significantly affect the fluid dynamics over large distances.
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| 3. |
- Elbourne, Aaron, et al.
(author)
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Adsorbed and near-surface structure of ionic liquids determines nanoscale friction
- 2013
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In: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 49:60, s. 6797-6799
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Journal article (peer-reviewed)abstract
- Surface-adsorbed and near-surface ion layer structure controls nanotribology in the silica-propylammonium nitrate (PAN)-mica system. Atomic Force Microscopy (AFM) imaging and normal force curves reveal that the normal load dictates the number of interfacial ion layers and the lateral layer structure. Shear force measurements show the lubricity of the interface changes with the number, and lateral structure, of the confined ion layer(s).
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| 4. |
- Skedung, Lisa, et al.
(author)
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Tribology, texture and touch
- 2014
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In: 5th World Tribology Congress, WTC 2013. - 9781634393522 ; , s. 2270-2273
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Conference paper (peer-reviewed)
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| 5. |
- Sweeney, James, et al.
(author)
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Control of Nanoscale Friction on Gold in an Ionic Liquid by a Potential-Dependent Ionic Lubricant Layer
- 2012
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 109:15, s. 155502-
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Journal article (peer-reviewed)abstract
- The lubricating properties of an ionic liquid on gold surfaces can be controlled through application of an electric potential to the sliding contact. A nanotribology approach has been used to study the frictional behavior of 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl) trifluorophosphate ([Py-1,Py-4]FAP) confined between silica colloid probes or sharp silica tips and a Au(111) substrate using atomic force microscopy. Friction forces vary with potential because the composition of a confined ion layer between the two surfaces changes from cation-enriched (at negative potentials) to anion-enriched (at positive potentials). This offers a new approach to tuning frictional forces reversibly at the molecular level without changing the substrates, employing a self-replenishing boundary lubricant of low vapor pressure.
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| 6. |
- Sweeney, James, et al.
(author)
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Effect of ion structure on nanoscale friction in protic ionic liquids
- 2014
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In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 16:31, s. 16651-16658
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Journal article (peer-reviewed)abstract
- The effect of ionic liquid (IL) molecular structure on nanoscale friction has been investigated using colloidal probe Friction Force Microscopy (FFM). The ILs studied were ethylammonium formate (EAF), ethylammonium nitrate (EAN), propylammonium formate (PAF), propylammonium nitrate (PAN), dimethylethylammonium formate (DMEAF), and ethanolammonium nitrate (EtAN). ILs were confined between a silica colloid probe and a mica surface, and the friction force was measured as a function of normal load for sliding velocities between 10 and 40 mu m s(-1). At low normal forces, multiple IL layers are found between the probe and the surface, but at higher force, in the boundary layer regime, a single ion layer separates the probe and the surface. In the boundary layer regime energy is dissipated by two main pathways. Firstly, the ionic liquid near the surface, with the exception of the boundary layer, is expelled from the advancing contact made by the probe on the surface. This disruption in the interactions between the boundary layer and the near surface multilayers, leads to energy dissipation and depends on the strength of the attraction between the boundary and near surface layers. The second pathway is via rotations and twists of ions in the boundary layer, primarily associated with the cation terminal methyl group. The friction coefficient did not vary over the limited range of sliding speeds investigated.
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