| 1. |
- Bergman, Kristoffer, et al.
(författare)
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Injectable cell-free template for bone-tissue formation
- 2009
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Ingår i: Journal of Biomedical Materials Research-Part A. - : Wiley Periodicals, Inc. - 1549-3296 .- 1552-4965. ; 91A:4, s. 1111-1118
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Tidskriftsartikel (refereegranskat)abstract
- Here we present a novel injectable hydrogel which forms a template for de novo formation of bone tissue. Hydrogel formation takes place in situ in less than 1 min by the cross-linking of multifunctional hyaluronic acid and polyvinyl alcohol derivatives. Endogenous cells are recruited in vivo by incorporating bone morphogenetic protein-2 (BMP-2), a powerful promoter for osteogenic differentiation. The hydrogel was evaluated in vitro by performing a cell viability test and a release study and in vivo by a rat ectopic model. Examination by X-ray, microcomputed tomography, and histology revealed a significant bone formation at the target site for gels containing BMP-2, and a complete degradation was observed for gels without BMP-2 four weeks after injection. There were no signs of inflammation or foreign body response in either group and we believe that this system has the potential as an off-the-shelf injectable to be used where bone tissue is needed.
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| 2. |
- Bexborn, Fredrik, et al.
(författare)
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Hirudin versus heparin for use in whole blood in vitro biocompatibility models
- 2009
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Ingår i: Journal of Biomedical Materials Research. Part A. - Hoboken, NJ, US : John Wiley & Sons Inc. - 1549-3296 .- 1552-4965. ; 89A:4, s. 951-959
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Tidskriftsartikel (refereegranskat)abstract
- Background: Heparin has traditionally been a widely used anticoagulant in blood research, but has been shown to be inappropriate for work with the complement system because of its complement-interacting properties. In this work, we have compared the effects of heparin with those of the specific thrombin inhibitor hirudin on complement and blood cells in vitro. Methods: Whole blood collected in the presence of hirudin (50 µg/mL) or heparin (1 IU/mL) was incubated in the slide chamber model. The plasma was analyzed for complement activation markers C3a and sC5b-9, and the polyvinylchloride test slides were stained for adhering cells. The integrity of the complement system was tested by incubating serum and hirudin-treated plasma in the presence of various activating agents.Results: In contrast to heparin, the addition of hirudin generally preserved the complement reactivity, and complement activation in hirudin plasma closely resembled that in normal serum. Importantly, immunochemical staining of surface-bound cells demonstrated the inducible expression of tissue factor on bound monocytes from hirudin-treated blood, an effect that was completely abolished in heparin-treated blood.Conclusion: Our results indicate that hirudin as an anticoagulant produces more physiological conditions than heparin, making hirudin well-suited for in vitro studies, especially those addressing the regulation of cellular processes.
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| 3. |
- Cairns, Marie-Louise, et al.
(författare)
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The potential of electron beam radiation for simultaneous surface modification and bioresorption control of PLLA.
- 2012
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Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 100:9, s. 2223-9
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Tidskriftsartikel (refereegranskat)abstract
- Bioresorbable polymers have been widely investigated as materials exhibiting significant potential for successful application in the fields of tissue engineering and drug delivery. Further to the ability to control degradation, surface engineering of polymers has been highlighted as a key method central to their development. Previous work has demonstrated the ability of electron beam (e-beam) technology to control the degradation profiles and bioresorption of a number of commercially relevant bioresorbable polymers (poly-l-lactic acid (PLLA), L-lactide/DL-lactide co-polymer (PLDL) and poly(lactic-co-glycolic acid (PLGA)). This work investigates the further potential of e-beam technology to impart added biofunctionality through the manipulation of polymer (PLLA) surface properties. PLLA samples were subjected to e-beam treatments in air, with varying beam energies and doses. Surface characterization was then performed using contact angle analysis, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and atomic force microscopy. Results demonstrated a significant increase in surface wettability post e-beam treatment. In correlation with this, XPS data showed the introduction of oxygen-containing functional groups to the surface of PLLA. Raman spectroscopy indicated chain scission in the near surface region of PLLA (as predicted). However, e-beam effects on surface properties were not shown to be dependent on beam energy or dose. E-beam irradiation did not seem to affect the surface roughness of PLLA as a direct consequence of the treatment.
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| 4. |
- Ferraz, Natalia, et al.
(författare)
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In vitro and in vivo toxicity of rinsed and aged nanocellulose-polypyrrole composites
- 2012
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Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 100A:8, s. 2128-2138
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Tidskriftsartikel (refereegranskat)abstract
- Novel composites of nanocellulose and the conducting polymer polypyrrole (PPy) are herein suggested as potential candidates for active ion-extraction membranes in electrochemically controlled hemodialysis. This work has defined processing parameters to obtain a biocompatible nanocellulose-PPy composite and for the first time, the effect of the composite ageing on cell viability has been studied.The influence of rinsing and extraction process steps, as well as ageing under different conditions (i.e. in air, at –20 ˚C and in argon), on the electroactivity and cytotoxicity of a PPy-nanocellulose composite has been investigated. The biocompatibility evaluation was based on indirect toxicity assays with fibroblasts and monocyte cell lines and an acute toxicity test in mice, while the electroactivity was evaluated by cyclic voltammetry experiments.The as-prepared composite did not induce any cytotoxic response in vitro or in vivo. Extensive rinsing and 48 hour incubation in biological buffer previous to the preparation of the culture medium extracts were, however, necessary to obtain a non-cytotoxic composite. The as-prepared composite was also found to exhibit acceptable electrochemical performance, which was retained upon 4 weeks storage in argon atmosphere. It was shown that ageing of the composite had a negative effect on biocompatibility, regardless of the storage condition. Thus, to allow for long time storage of electroactive nanocellulose-PPy hemodialysis membranes, the degradation of PPy upon storage must be controlled. The present results show that the biocompatibility of PPy composites depends on the rinsing and pre-treatment of the composite material as well as the aging of the material.
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| 5. |
- Ferraz, Natalia, et al.
(författare)
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Nanoporesize affects complement activation
- 2008
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Ingår i: Journal of biomedical materials research. Part A. - : Wiley. - 1552-4965 .- 1549-3296. ; 87:3, s. 575-81
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, we have shown the vast importance of biomaterial nanotexture when evaluating inflammatory response. For the first time in an in vitro whole blood system, we have proven that a small increase in nanoporesize, specifically 180 nm (from 20 to 200 nm), has a huge effect on the complement system. The study was done using nanoporous aluminiumoxide, a material that previously has been evaluated for potential implant use, showing good biocompatibility. This material can easily be manufactured with different pore sizes making it an excellent candidate to govern specific protein and cellular events at the tissue-material interface. We performed whole blood studies, looking at complement activation after blood contact with two pore size alumina membranes (pore diameters, 20 and 200 nm). The fluid phase was analyzed for complement soluble components, C3a and sC5b-9. In addition, surface adsorbed proteins were eluted and dot blots were performed to detect IgG, IgM, C1q, and C3. All results point to the fact that 200 nm pore size membranes are more complement activating. Significantly, higher values of complement soluble components were found after whole blood contact with 200 nm alumina and all studied proteins adsorbed more readily to this membrane than to the 20 nm pore size membrane. We hypothesize that the difference in complement activation between our two test materials is caused by the type and the amount of adsorbed proteins, as well as their conformation and orientation. The different protein patterns created on the two alumina membranes are most likely a consequence of the material topography.
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| 6. |
- Fink, Helen, 1978, et al.
(författare)
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An in vitro study of blood compatibility of vascular grafts made of bacterial cellulose in comparison with conventionally-used graft materials
- 2011
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Ingår i: Journal of Biomedical Materials Research - Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 97A:1, s. 52-58
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Tidskriftsartikel (refereegranskat)abstract
- In this study we analyzed the blood compatibility of bacterial cellulose (BC) as a new biosynthetic material for use as a vascular graft. As reference materials we used expanded polytetrafluoroethylene (ePTFE) and poly(ethylene terephthalate) (PET) vascular grafts. These materials are in clinical use today. Tubes with inner diameters of both 4 (not PET) and 6 mm were tested. Heparin-coated PVC tubes (hepPVC) were used as a negative control. Platelet consumption and thrombin-antithrombin complex (TAT) were used as parameters of coagulation and for complement activation, sC3a and sC5b-9 were used. The investigated parameters were measured after 1-h exposure to freshly drawn human blood supplemented with a low dose of heparin in a Chandler loop system. The results showed that BC exhibits no significant difference in platelet consumption, as compared with PET 16 mm), ePTFE and hepPVC. The PET material consumed more platelets than any of the other materials. The TAT generation for 4 mm tubes was not significantly different between BC and the other materials. For 6 mm tubes, however, differences were observed between hepPVC and PET (p < 0.0001); BC and hepPVC (p = 0.0016); ePTFE and PET (p < 0.0001); BC and ePTFE (p = 0.0029); BC and PET (p = 0.0141). Surprisingly, considering the low platelet consumption, the complement activation parameters (sC3a and sC5b-9) were much higher for BC, as compared with the other materials for both 4 and 6 mm tubes.
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| 7. |
- Han, Yilin, et al.
(författare)
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Effect of scaffold properties on adhesion and maintenance of boundary cap neural crest stem cells in vitro
- 2020
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Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 108:6, s. 1274-1280
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Tidskriftsartikel (refereegranskat)abstract
- Optimal combination of stem cells and biocompatible support material is a promising strategy for successful tissue engineering. The required differentiation of stem cells is crucial for functionality of engineered tissues and can be regulated by chemical and physical cues. Here we examined how boundary cap neural crest stem cells (bNCSCs) are affected when cultured in the same medium, but on collagen- or laminin-polyacrylamide (PAA) scaffolds of different stiffness (0.5, 1, or similar to 7 kPa). bNCSCs displayed marked differences in their ability to attach, maintain a large cell population and differentiate, depending on scaffold stiffness. These findings show that the design of physical cues is an important parameter to achieve optimal stem cell properties for tissue repair and engineering.
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| 8. |
- Hoess, Andreas, et al.
(författare)
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Self-supporting nanoporous alumina membranes as substrates for hepatic cell cultures
- 2012
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Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 100A:9, s. 2230-2238
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Tidskriftsartikel (refereegranskat)abstract
- Membranes made from nanoporous alumina exhibit interesting properties for their use in biomedical research. They show high porosity and the pore diameters can be easily adjusted in a reproducible manner. Nanoporous alumina membranes are thus ideal substrates for the cultivation of polar cells (e.g., hepatocytes) or the establishment of indirect co-cultures. The porous nature of the material allows supply of nutrients to both sides of adherent cells and the exchange of molecules across the membrane. However, it is well-known that surface features in the nanometer range affect cellular behavior. In this study, the response of HepG2 cells to nanoporous alumina membranes with three different pore diameters, ranging from 50 to 250 nm, has been evaluated. The cellular interactions with the nanoporous materials were assessed by investigating cell adhesion, morphology, and proliferation. Cell functionality was measured by means of albumin production. The membranes supported good cell adhesion and spreading. Compared to tissue culture plastic, the cells on the porous substrates developed distinct focal adhesion sites and actin stress fibers. Additionally, electron microscopical investigations revealed the penetration of cellular extensions into pores with diameters bigger than 200 nm. Furthermore, cell proliferation significantly increased with an increase in pore diameter, whereas the albumin production followed a reverse trend. Thus, it seems to be possible to direct cellular behavior of HepG2 cells growing on nanoporous alumina by changing the pore diameter of the material. Hence, nanoporous alumina membranes can be useful culture substrates to develop new approaches in the field of liver tissue engineering.
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| 9. |
- Hulsart-Billström, Gry, et al.
(författare)
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Osteogenic potential of Sr-doped calcium phosphate hollow spheres in vitro and in vivo
- 2013
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Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 101:8, s. 2322-2331
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Tidskriftsartikel (refereegranskat)abstract
- Treatment of osteoporotic fractures with conventional surgical methods is associated with a high rate of complications. Intense search for new treatment options includes development of specific biomaterials aimed to be part of the surgical armamentarium. Strontium doped calcium phosphate spheres (SrCPS) is a new material that might be of interest due to the influence on osteoclast and osteoblast activity. In the present study, we successfully constructed hollow spherical SrCPS particles with a diameter of ∼700 nm and shell thickness of ∼150 nm. The Sr content was about 20 wt %. Cell viability and cytotoxicity were investigated in vitro with concentrations from 0 to 1000 μg/mL of SrCPS in medium extract in a day chase study. The in vivo biocompatibility was tested in a delayed bone-healing model in a rat vertebral defect by histology, μCT, and nanoSPECT. The SrCPS showed no toxicity in vitro with comparable cell number in all concentrations. Increased metabolism was seen in the cell viability study in cells exposed to 400 and 600 μg/mL. SPECT showed good biocompatibility with no local adverse effects and an increased osteoblast activity as compared to adjacent vertebra. SrCPS implantation induced bone formation and resulted in complete resorption and defect consolidation.
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| 10. |
- Jarmar, T., et al.
(författare)
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Technique for preparation and characterization in cross-section of oral titanium implant surfaces using focused ion beam and transmission electron microscopy
- 2008
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Ingår i: Journal of Biomedical Materials Research Part A. - : Wiley. - 1552-4965 .- 1549-3296. ; 87:4, s. 1003-9
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Tidskriftsartikel (refereegranskat)abstract
- The surface properties of materials are believed to control most of the biological reactions toward implanted materials. To study the surface structure, elemental distribution, and morphology, using transmission electron microscopy (TEM) techniques, thin foils of the surface (in cross-section) are needed. These have been cumbersome to produce, in particular, from the normally irregular screw-shaped metal implants. Focused ion beam (FIB) microscopy has been developed partly for TEM sample preparation, mainly within the microelectronics industry. Our study describes a method based on FIB for producing electron transparent foils/sections from a metal implant for TEM analysis. Using a screw-shaped titanium dental implant, it was demonstrated that thin foils can be prepared with submicron specificity and from almost any surface geometry. A comparison of different lift-out techniques showed that the in situ lift-out preparation technique allowed plasma cleaning and produced particularly good samples with excellent yield. The titanium oxide on the implant surface was analyzed using energy-filtered TEM (EFTEM) and high-resolution TEM (HRTEM) and the TiO(2) rutile phase being determined via the lattice parameters. This study provides the first set of data for the optimization of a new route for preparation and analysis of biomaterial surfaces and interfaces.
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