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- Bergstrand, Anna, 1974, et al.
(author)
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Preparation of Porous Poly(3-Hydroxybutyrate) Films by Water-Droplet Templating
- 2012
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In: Journal of Biomaterials and Nanobiotechnology. - : Scientific Research Publishing, Inc.. - 2158-7027 .- 2158-7043. ; 3
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Journal article (peer-reviewed)abstract
- Porous resorbable implants are of great interest since they may deliver bioactives or drugs, facilitate the transport of body fluids or degradation products and provide a favorable environment for cell attachment and growth. In this work we report on a method using concentrated emulsions to template interconnected solid foam materials and to produce highly porous poly(3-hydroxybutyrate) (PHB) materials. Porous PHB films were cast made from water-in-oil template emulsions including Span 80 and lithium sulphate. The films were characterized by SEM-EDX and DMA. The water uptake of the films was recorded in order to determine the fraction water available pores. The results show that the ad-dition of lithium sulphate allows a fine tuning of the film morphology with respect to porosity and interconnected po-rous structure. The film porosity was determined to 51% ± 3%, 52% ± 3% and 45% ± 3% for the films made with 0%, 2.9% and 14.3% lithium sulphate in the template emulsion, respectively. The fraction water available pores was sig-nificantly lower, 11% ±3%, 38% ±12% and 48% ± 7% for films with 0%, 2.9% and 14.3% litium sulphate respectively. Differences in fraction water available pores and total porosity for the films reflects the film morphology and differ-ences in pore interconnection.
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| 2. |
- Thorfve, Anna, 1982, et al.
(author)
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Gene Expression Profiling of Peri-Implant Healing of PLGA-Li+ Implants Suggests an Activated Wnt Signaling Pathway In Vivo
- 2014
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In: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 9:7
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Journal article (peer-reviewed)abstract
- Bone development and regeneration is associated with the Wnt signaling pathway that, according to literature, can be modulated by lithium ions (Li+). The aim of this study was to evaluate the gene expression profile during peri-implant healing of poly(lactic-co-glycolic acid) (PLGA) implants with incorporated Li+, while PLGA without Li+ was used as control, and a special attention was then paid to the Wnt signaling pathway. The implants were inserted in rat tibia for 7 or 28 days and the gene expression profile was investigated using a genome-wide microarray analysis. The results were verified by qPCR and immunohistochemistry. Histomorphometry was used to evaluate the possible effect of Li+ on bone regeneration. The microarray analysis revealed a large number of significantly differentially regulated genes over time within the two implant groups. The Wnt signaling pathway was significantly affected by Li+, with approximately 34% of all Wnt-related markers regulated over time, compared to 22% for non-Li+ containing (control; Ctrl) implants. Functional cluster analysis indicated skeletal system morphogenesis, cartilage development and condensation as related to Li+. The downstream Wnt target gene, FOSL1, and the extracellular protein-encoding gene, ASPN, were significantly upregulated by Li+ compared with Ctrl. The presence of beta-catenin, FOSL1 and ASPN positive cells was confirmed around implants of both groups. Interestingly, a significantly reduced bone area was observed over time around both implant groups. The presence of periostin and calcitonin receptor-positive cells was observed at both time points. This study is to the best of the authors' knowledge the first report evaluating the effect of a local release of Li+ from PLGA at the fracture site. The present study shows that during the current time frame and with the present dose of Li+ in PLGA implants, Li+ is not an enhancer of early bone growth, although it affects the Wnt signaling pathway.
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| 5. |
- Bergstrand, Anna, 1974
(author)
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Biomolecules at Interfaces -Studied by Surface and Solution Techniques
- 2007
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Doctoral thesis (other academic/artistic)abstract
- The interfacial behaviour of biomolecules in general and proteins in particular is interesting from a biochemical point of view since proteins are involved in processes such as complement activation, blood coagulation and atherosclerotic plaque formation, but also in the context of biomedical applications such as solid-phase diagnostics, therapeutic aphaeresis and biosensors. The objective of this thesis is to study biomolecular interactions using surface sensitive biosensor techniques such as surface plasmon resonance, SPR, in combination with bulk techniques.Lipopolysaccharide, LPS, is as a key mediator of sepsis mediated syndromes. Removal of circulating LPS by therapeutic aphaeresis, achieved by LPS-binding molecules that are anchored to a solid support, has been suggested as an adjuvant sepsis therapy. Anti-LPS peptides, designed from LPS-binding molecules, were covalently immobilized on model surfaces. The effect of immobilization on the LPS-binding ability of the peptides and the stability of the interaction was studied. Covalently attached peptides retained their activity although to varying extent. The LPS binding capacity of the peptides was in some cases dependent on the immobilization method. Furthermore, the solution behaviour of LPS in terms of aggregation onset and aggregate size was studied. It was found that LPS aggregated into spherical aggregates in a continuous manner at close to physiological conditions, possibly reflecting the polydispersity of the molecule. Suppression of non-specific protein adsorption is essential for biosensors applications in order to achieve sufficient selectivity and sensitivity and for blood contacting devices in order to avoid immune responses or blood coagulation. This can be accomplished with PEG-functionalized coatings. The effect of interfacial charge on the protein rejecting ability of two PEGylated copolymers was monitored. The results indicate that an adsorbed layer of PEGylated copolymers can be very efficient in preventing proteins from adsorbing at a surface provided there is charge matching between the polyelectrolyte and the underlying surface. Inadequate diagnosis contributes to the high mortality records of severe sepsis. Direct detection of elevated plasma levels of protein-bound isopeptides, from the disseminated intravascular coagulation that occurs in severe sepsis, could constitute a useful diagnostic marker. The interaction between an immobilized anti-isopeptide antibody and a protein-bound isopeptide was studied by SPR with the intention to develop a SPR based immunoassay for the diagnosis of sepsis. This first study shows that this direct assay has a high immunocapturing efficiency and detects protein-bound isopeptides in buffer and diluted plasma. Finally, the combined use of two surface sensitive biosensor techniques, SPR and quartz crystal microbalance with dissipation monitoring, QCM-D, was explored for the study of the interaction between low density lipoprotein, LDL and the proteoglycan decorin. LDL affinity to proteoglycans is a potential marker for atherogenic LDL that may be used in a clinical solid-phase or biosensor assay for atherosclerosis risk prediction.
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| 6. |
- Bergstrand, Anna, 1974, et al.
(author)
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Comparison of PEI-PEG and PLL-PEG Copolymer Coatings on the Prevention of Protein Fouling
- 2009
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In: Journal of Biomedical Materials Research - Part A. - : Wiley. - 1552-4965 .- 1549-3296. ; 88:3, s. 608-615
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Journal article (peer-reviewed)abstract
- The effect of surface charge on the protein resistance of adsorbed layers of poly(ethylene imine)-[g]poly(ethylene glycol), PEI-PEG, and poly(L-lysine)-[g]poly(ethylene glycol), PLL-PEG, was studied. Mixed and monofunctional self-assembled monolayers, SAMs, on gold were obtained by adsorption of 16-mercapto-1-hexadecanoic acid and 16-mercapto-1-hexadecanol. The surface charge was systematically varied by changing the ratio of the two alkanethiols. The graft copolymers PEI-PEG and PLL-PEG were adsorbed at the SAMs and tested for resistance towards human serum albumin and fibrinogen. The adsorbed amount of copolymers increased with increasing negative surface charge. However, the best protein resistance was found at an intermediate surface charge. The PLL-PEG covered Surfaces showed better protein resistance than the PEI-PEG covered surfaces. Thus, this work demonstrates that an adsorbed layer of PEG-grafted PEI and, in particular, PEG-grafted PLL is efficient in preventing protein adsorption when there is charge neutralization between the copolymer and the underlying surface.
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| 7. |
- Bergstrand, Anna, 1974, et al.
(author)
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Permeability of Porous Poly(3-hydroxybutyrate) Barriers of Single and Bilayer Type for Implant Applications
- 2014
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In: International Journal of Polymer Science. - : Hindawi Limited. - 1687-9430 .- 1687-9422. ; 2014, s. Art. no. 958975-
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Journal article (peer-reviewed)abstract
- Poly(3-hydroxybutyrate) (PHB) is a polyester which shows excellent biocompatibility and a PHB material is therefore considered suitable for many biomedical applications. A highly porous PHB material may be designed to facilitate the transport of small molecules and body fluids or serve as a biocompatible temporary barrier. In this study, PHB films with varying degree of porosity and pore interconnectivity were made by solvent casting using water-in-oil emulsion templates of varying composition. The morphology was characterized by SEM and the water permeability of the films was determined. The results show that an increased water content of the template emulsion resulted in a film with increased porosity. A fine tuning of the film morphology of the casted films was achieved by varying the salt content of the water phase of the template emulsion. It was concluded that the major determinant of the water permeability through these films is the pore interconnectivity. Furthermore, we report on the formation and water permeability of bilayer PHB films consisting of a porous layer combined with a dense backing layer.
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| 9. |
- Bergstrand, Anna, 1974, et al.
(author)
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Towards a biosensor immunoassay of protein-bound isopeptides in human plasma
- 2008
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In: Colloids and Surfaces B: Biointerfaces. - 0927-7765 .- 1873-4367. ; 66, s. 150-
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Journal article (peer-reviewed)abstract
- This study demonstrates that synthetic isopeptides formed on BSA can be quantitatively analyzed by a surface plasmon resonance-based biosensor method. A monoclonal IgM antibody 81D4, that reacts with the synthetic isopeptide and also with the natural isopeptide cross-link in D-dimer (but not with its non-cross-linked fibrin monomer), was covalently immobilized to a carboxymethylated dextran surface, a CM5 surface. Its immunocapturing efficiency was found to be good. The affinity of the interaction between the monoclonal 81D4 and the synthetic isopeptide was estimated to approximately 4x10(-7)M. Good reactivity was also observed when human plasma spiked with this isopeptide was used as test solution. Cross-linked D-dimer in the plasma of patients is a marker of disseminated intravascular coagulation (DIC) which occurs late in sepsis. This biosensor method has the potential to be developed into a rapid sensitive assay for measuring the level of natural isopeptide cross-links in proteins in the plasma of patients with a suspected diagnosis of sepsis.
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| 10. |
- Bergstrand, Anna, 1974-, et al.
(author)
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Varför är det så snårigt? : Begrepp relaterade till samverkansmeritering
- 2021
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Reports (pop. science, debate, etc.)abstract
- Detta dokument är framtaget som en intern rapport inom MerSam – Meritvärde av samverkansskicklighet, varsprojekttid löpt under 2017 – 2020. MerSam är ett av Vinnovas 17 finansierade K3-projekt. Rapporten utgör ensammanställning av insamlad information från dokument, dialoger, workshoppar, intervjuer och enkäter.Rapporten visar på användning av begrepp och tolkning av begrepp. Syftet är att beskriva en nulägesbild ochutifrån den samla och lyfta fram vilka begrepp som förslagsvis kan användas i projektets slutleveranser. Slutsatser och rekommendationer har tagits fram med delaktighet av hela MerSam projektet och hardiskuterats på projektmöten, projektworkshopar den 17-18 juni 2020 samt den 15 oktober 2020.
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