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| 2. |
- Breitbach, Martin, et al.
(författare)
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Potential risks of bone marrow cell transplantation into infarcted hearts
- 2007
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Ingår i: Blood. - Washington, DC : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 110:4, s. 1362-1369
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Tidskriftsartikel (refereegranskat)abstract
- Cellular replacement therapy has emerged as a novel strategy for the treatment of heart failure. The aim of our study was to determine the fate of injected mesenchymal stem cells (MSCs) and whole bone marrow (BM) cells in the infarcted heart. MSCs were purified from BM of transgenic mice and characterized using flow cytometry and in vitro differentiation assays. Myocardial infarctions were generated in mice and different cell populations including transgenic MSCs, unfractionated BM cells, or purified hematopoietic progenitors were injected. Encapsulated structures were found in the infarcted areas of a large fraction of hearts after injecting MSCs (22 of 43, 51.2%) and unfractionated BM cells (6 of 46, 13.0%). These formations contained calcifications and/or ossifications. In contrast, no pathological abnormalities were found after injection of purified hematopoietic progenitors (0 of 5, 0.0%), fibroblasts (0 of 5, 0.0%), vehicle only (0 of 30, 0.0%), or cytokine-induced mobilization of BM cells (0 of 35, 0.0%). We conclude that the developmental fate of BM-derived cells is not restricted by the surrounding tissue after myocardial infarction and that the MSC fraction underlies the extended bone formation in the infarcted myocardium. These findings seriously question the biologic basis and clinical safety of using whole BM and in particular MSCs to treat nonhematopoietic disorders.
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| 3. |
- Kolossov, Eugen, et al.
(författare)
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Engraftment of engineered ES cell-derived cardiomyocytes but not BM cells restores contractile function to the infarcted myocardium
- 2006
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Ingår i: Journal of Experimental Medicine. - New York, USA : Rockefeller University Press. - 0022-1007 .- 1540-9538. ; 203:10, s. 2315-2327
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Tidskriftsartikel (refereegranskat)abstract
- Cellular cardiomyoplasty is an attractive option for the treatment of severe heart failure. It is, however, still unclear and controversial which is the most promising cell source. Therefore, we investigated and examined the fate and functional impact of bone marrow (BM) cells and embryonic stem cell (ES cell)-derived cardiomyocytes after transplantation into the infarcted mouse heart. This proved particularly challenging for the ES cells, as their enrichment into cardiomyocytes and their long-term engraftment and tumorigenicity are still poorly understood. We generated transgenic ES cells expressing puromycin resistance and enhanced green fluorescent protein cassettes under control of a cardiac-specific promoter. Puromycin selection resulted in a highly purified (>99%) cardiomyocyte population, and the yield of cardiomyocytes increased 6-10-fold because of induction of proliferation on purification. Long-term engraftment (4-5 months) was observed when co-transplanting selected ES cell-derived cardiomyocytes and fibroblasts into the injured heart of syngeneic mice, and no teratoma formation was found (n = 60). Although transplantation of ES cell-derived cardiomyocytes improved heart function, BM cells had no positive effects. Furthermore, no contribution of BM cells to cardiac, endothelial, or smooth muscle neogenesis was detected. Hence, our results demonstrate that ES-based cell therapy is a promising approach for the treatment of impaired myocardial function and provides better results than BM-derived cells.
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| 4. |
- Bazooyar, Faranak, 1972, et al.
(författare)
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Computational studies of water and carbon dioxide interactions with cellobiose
- 2015
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Ingår i: Journal of Molecular Modeling. - : Springer Science and Business Media LLC. - 0948-5023 .- 1610-2940. ; 21:1, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- B3LYP/6-311++G** with dispersion correction (DFT-D) was used to study local and global minimum energy structures of water (H2O) or carbon dioxide (CO2) bonding with a pair of cellobiose molecules. The calculations showed that neither the H2O nor the CO2 prefer to be between the cellobiose molecules, and that the minimum energy structures occur when these molecules bond to the outer surface of the cellobiose pair. The calculations also showed that the low energy structures have a larger number of inter-cellobiose hydrogen bonds than the high energy structures. These results indicate that penetration of H2O or CO2 between adjacent cellobiose pairs, which would assist steam or supercritical CO2 (SC-CO2) explosion of cellulose, is not energetically favored. Comparison of the energies obtained with DFT-D and DFT (the same method but without dispersion correction) show that both hydrogen bonds and van der Waals interactions play an important role in cellobiose-cellobiose interactions.
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| 5. |
- Bohlén, Martin, 1978
(författare)
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Computational Studies of Poly(vinylidene fluoride)
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Poly(vinylidene fluoride) (PVDF) is a versatile material with numerous applications, both potential and realized, in many industrial sectors. The extent of applications, ranging from cable and wire products, to sensors for the monitoring of respiration and heart-rate in medicine, indicates on the level of interest the materials science community has for this material. PVDF has the potential to be used in applications where its piezoelectric characteristics are utilized, but for this to be realized, a specific crystal structure, the polar β-phase, need to be present in the material. Since PVDF is polymorphic and usually crystallizes from melt or from solution into the non-polar α-phase, which is of little use in piezoelectric applications, the induction of the β-phase is an active field of research. With computational methods it is possible to study PVDF on a molecular level to gain better insights into the mechanisms behind the formation of this specific crystal structure. Conformational studies of PVDF, the effect of carbon nanotubes on the conformation as well as the mechanical properties of PVDF, copolymerization with trifluoroethylene and the effect of increased temperatures and pressures have been studied using molecular mechanics/dynamics and first principles methods. It has been found that carbon nanotubes mainly act as nucleating agents for the formation of β-phase PVDF as their effect on the mechanical properties of PVDF is relatively small. Furthermore, β-phase formation can be facilitated with very rapid cooling rates from the melt, hindering the transformation into the thermodynamically stable α-phase and by inclusion of trifluoroethylene units in the PVDF chain. With better insights into the mechanism of β-phase PVDF formation, it would ideally be possible to produce piezoelectric PVDF with better characteristics and possibly also in new and more efficient ways.
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| 6. |
- Bohlén, Martin, 1978
(författare)
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Computational studies of Poly(vinylidene fluoride) and Poly(vinylidene fluoride) - Single Wall Carbon Nanotube Composites
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Poly(vinylidene fluoride) (PVDF) exhibits properties that allows the material to be used in such diverse areas as wire and cable products, electronic devices, membranes, exterior coatings for constructions and in the chemical, pharmaceutical and food industry as fluid-handling equipment. It is the inherent molecular structure of PVDF, where every second backbone carbon is bonded to two fluorine atoms, that gives the polymer several unique properties, among them piezo- and pyroelectricity. However, to obtain a material with a high piezoelectric activity, the amount of the crystal phase with the largest polarization, the β crystal phase, has to be large. Possibly, this could be achieved by the addition of different types of additives, carbon nanotubes (CNTs) being one of them. In this study, molecular modeling of PVDF and PVDF-single wall carbon nanotubes (SWCNTs) composites has been performed. Also, the molecular structure of PVDF around and above the melting point has been investigated using both computational and experimental techniques. The results obtained from first principles, molecular mechanics (MM) and molecular dynamics (MD) studies indicate that PVDF molecules have a larger affinity to be in the all-trans structure similar to the polar β-phase at temperatures above the melting point. However, when melt or solution cast the main PVDF crystal phase obtained is the non-polar α-phase. A prevention of this phase transformation from β to α during crystallization could yield a material with a strong piezoelectric effect. Furthermore, MM and MD studies of the mechanical properties of PVDF and PVDF-SWCNT nanocomposites showed that the reinforcing effect of SWCNTs on PVDF is dependent on the alignment of the SWCNTs. When aligned in the direction of applied stress, an increase of the Young’s modulus of about 1 GPa could be observed. A simulation of a pullout of a SWCNT from a PVDF matrix revealed that the interfacial shear stress is in the same range as other polymer-SWCNT systems and that this interface possibly can be strengthened by functionalization of the pristine carbon nanotubes.
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| 7. |
- Bohlén, Martin, et al.
(författare)
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Computational Studies of Poly(vinylidene fluoride)-Single Wall Carbon Nanotube Systems
- 2013
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Ingår i: Journal of Computational and Theoretical Nanoscience. - : American Scientific Publishers. - 1546-1955 .- 1546-1963. ; 10:6, s. 1317-1325
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Tidskriftsartikel (refereegranskat)abstract
- First principles and molecular mechanics methods have been used to study poly(vinylidene fluoride)—single wall carbon nanotube systems. First principles calculations (Møller-Plesset second order perturbation theory and density functional theory with B3LYP exchange correlation functional with and without dispersion correction) using short poly(vinylidene fluoride) segments and short hydrogen-capped single wall carbon nanotubes show that the polymer segments prefer to have the β-rather than the β-conformation both in the absence and presence of the single wall carbon nanotube. The lowest energy structure is obtained when the poly(vinylidene fluoride) has an β-conformation and is located parallel to the single wall carbon nanotube wall. In contrast to the Dreiding and Universal force fields, the COMPASS force field predicts the structures containing the β-conformation of poly(vinylidene fluoride) to be the lowest in energy in agreement with first principles results. The COMPASS force field was consequently used in preliminary studies of a longer poly(vinylidene fluoride) chain and a longer single wall carbon nanotube using molecular dynamics.
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| 8. |
- Bohlén, Martin, et al.
(författare)
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Conformational studies of poly(vinylidene fluoride), poly(trifluoroethylene) and poly(vinylidene fluoride-co-trifluoroethylene) using density functional theory
- 2014
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : R S C Publications. - 1463-9076 .- 1463-9084. ; 16:25, s. 12929-12939
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Tidskriftsartikel (refereegranskat)abstract
- Different conformations of systems consisting of poly(vinylidene fluoride) (PVDF), poly(trifluoroethylene) (PTrFE) and poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) were investigated using density functional theory with dispersion correction. It was found that the trans-gauche-trans-gauche´ (TGTG´) conformation of a single PVDF chain is the lowest energy conformer. Crystals of PVDF were modelled using between two to five chains with up to 12 repeat units in each chain and, in agreement with experiment, structures comprised partly or completely of chains with the TGTG´ conformation are more stable than structures built up from chains with all-trans (TTTT) conformation. This indicates that an all-trans segment or chain will not induce the growth of a larger crystal with the same chain conformations. In contrast, the energetically preferred structure of PTrFE chains is an all-trans (TTTT) conformation, and the results indicate that copolymerization of vinylidene fluoride with trifluoroethylene can facilitate the formation of the all-trans PVDF conformations. This is probably due to increased intramolecular repulsion between the fluorine atoms and an increased intermolecular attraction in the crystal structure.
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| 9. |
- Bohlén, Martin, et al.
(författare)
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Effect of single wall carbon nanotubes on the conformation of Poly(vinylidene fluoride)
- 2014
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Ingår i: Quantum Matter. - : American Scientific Publishers. - 2164-7615 .- 2164-7623. ; 3:4, s. 339-343
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Tidskriftsartikel (refereegranskat)abstract
- Structures consisting of single Poly(vinylidene fluoride) (PVDF) chains, single wall carbon nanotubes (SWCNTs), a PVDF chain interacting with a SWCNT and of five PVDF chains arranged to resemble the α and β crystal structures of PVDF were evaluated using geometry optimizations and single point energy calculations. Density functional theory with dispersion correction was used for all calculations. The conformer of PVDF is the lowest energy structure, irrespective of whether the SWCNT is present or not. Interaction with the SWCNT reduces the energy difference between the β and α conformers by approximately 30%, indicating that SWCNTs can increase the relative amount of the β conformers at higher temperatures. However, even in the presence of the SWCNT this energy difference is approximately 1.67 kcal/mol per –CH2CF2– repeat unit, which is larger than kT at 300 K (0.6 kcal/mol). Hence, the presence of the SWCNTs is not expected to substantially increase the relative amount of the β conformers at these conditions. Compression of the α and β crystal structures, which occurs during fibre extrusion, and which may be increased if nanoparticles are present in the polymer matrix, further decreases the energy difference between the β and α conformers but only to a very small extent at pressures relevant to fibre extrusion.
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| 10. |
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