| 1. |
- Alffram, Per-Axel, et al.
(författare)
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Implantation of the Femoral Stem into a Bed of Titanium Granules Using Vibration: A pilot study of a new method for prosthetic fixation in 5 patients followed for up to 15 years
- 2007
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Ingår i: Uppsala Journal of Medical Sciences. - 0300-9734. ; 112:2, s. 183-189
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Tidskriftsartikel (refereegranskat)abstract
- This study describes a new method for the fixation of titanium hip stem prostheses based on interdigitation of irregularly shaped porous titanium granules onto bone tissue. The granules were distributed into the prepared femoral cavity using a vibrating tool, and the stem was vibrated and tapped into the bed of granules. In this pilot study, 5 patients were followed between 9 and 15 years. The clinical results were excellent and the prostheses remained stable. Autopsy (one specimen) and computer tomography (three patients) show that the granules become incorporated by bone ingrowth.
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| 2. |
- Eriksson Linsmeier, Cecilia, et al.
(författare)
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Soft tissue reactions evoked by implanted gallium phosphide.
- 2008
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Ingår i: Biomaterials. - : Elsevier BV. - 1878-5905 .- 0142-9612. ; 29:35, s. 4598-4604
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Tidskriftsartikel (refereegranskat)abstract
- Neural devices may play an important role in the diagnosis and therapy of several clinical conditions, such as stroke, trauma or neurodegenerative disorders, by facilitating motor and pain control. Such interfaces, chronically implanted in the CNS, need to be biocompatible and have the ability to stimulate and record nerve signals. However, neural devices of today are not fully optimized. Nanostructured surfaces may improve electrical properties and lower evoked tissue responses. Vertical gallium phosphide (GaP) nanowires epitaxially grown from a GaP surface is one way of creating nanostructured electrodes. Thus, we chose to study the soft tissue reactions evoked by GaP surfaces. GaP and the control material titanium (Ti) were implanted in the rat abdominal wall for evaluation of tissue reactions after 1, 6, or 12 weeks. The foreign-body response was evaluated by measuring the reactive capsule thickness and by quantification of ED1-positive macrophages and total cells in the capsule. Furthermore, the concentration of Ga was measured in blood, brain, liver and kidneys. Statistically significant differences were noticed between GaP and Ti at 12 weeks for total and ED1-positive cell densities in the capsule. The chemical analysis showed that the concentration of Ga in brain, liver and kidneys increased during 12 weeks of implantation, indicating loss of Ga from the implant. Taken together, our results show that the biocompatible properties of GaP are worse than those of the well-documented biomaterial Ti.
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| 3. |
- Asplund, Basse, et al.
(författare)
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In vitro degradation and in vivo biocompatibility study of a new linear poly(urethane urea)
- 2008
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Ingår i: Journal of biomedical materials research. Part B: Applied biomaterials. - : Wiley. - 1552-4973 .- 1552-4981. ; 86B:1, s. 45-55
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Tidskriftsartikel (refereegranskat)abstract
- Segmented poly(urethane urea)s (PUUs) with hard segments derived only from methyl 2,6-diisocyantohexanoate (LDI) without the use of a chain extender have previously been described. These materials, which contain hard segments with multiple urea linkages, show exceptionally high strain capability (1600-4700%). In the study reported here, the rate and effect of hydrolysis of these materials were determined for gamma-sterilized and nonsterilized samples. Materials investigated contained PCL, PTMC, P(TMC-co-CL), P(CL-co-DLLA), or P(TMC-co-DLLA) as soft segments and, as well as their mechanical properties, changes in mass, inherent viscosity (IN.), and thermal properties were studied over 20 weeks. Results showed that the degradation rate was dependant on the soft segment structure, with a higher rate of degradation for the polyester-dominating PUUs exhibiting a substantial loss in IN. A tendency of reduction of tensile strength and strain hardening was seen for all samples. Also, loss in elongation at break was detected, for PUU-P(CL-DLLA) it went from 1600% to 830% in 10 weeks. Gamma radiation caused an initial loss in I.V. and induced more rapid hydrolysis compared with nonsterilized samples, except for PUU-PTMC. A cytotoxicity test using human fibroblasts demonstrated that the material supports cell viability. In addition, an in vivo biocompatibility study showed a typical foreign body reaction after I and 6 weeks.
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| 4. |
- Brammer, Karla S., et al.
(författare)
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Improved bone-forming functionality on diameter-controlled TiO2 nanotube surface
- 2009
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Ingår i: Acta Biomaterialia. - : Elsevier BV. - 1878-7568 .- 1742-7061. ; 5:8, s. 3215-3223
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Tidskriftsartikel (refereegranskat)abstract
- The titanium dioxide (TiO2) nanotube surface enables significantly accelerated osteoblast adhesion and exhibits strong bonding with bone. We prepared various sizes (30-100 nm diameter) of titanium dioxide (TiO2) nanotubes on titanium substrates by anodization and investigated the osteoblast cellular behavior in response to these different nanotube sizes. The unique and striking result of this study is that a change in osteoblast behavior is obtained in a relatively narrow range of nanotube dimensions, with small diameter (similar to 30 nm) nanotubes promoting the highest degree of osteoblast adhesion, while larger diameter (70-100 nm) nanotubes elicit a lower population of cells with extremely elongated cellular morphology and much higher alkaline phosphatase levels. Increased elongation of nuclei was also observed with larger diameter nanotubes. By controlling the nanotopography, large diameter nanotubes, in the similar to 100 min regime, induced extremely elongated cellular shapes, with an aspect ratio of 11:1, which resulted in substantially enhanced up-regulation of alkaline phosphatase activity, suggesting greater bone-forming ability than nanotubes with smaller diameters. Such nanotube structures, already being a strongly osseointegrating implant material, offer encouraging implications for the development and optimization of novel orthopedics-related treatments with precise control toward desired cell and bone growth behavior. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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| 5. |
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| 6. |
- Hilborn, Jöns, et al.
(författare)
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A new and evolving paradigm for biocompatibitity
- 2007
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Ingår i: Journal of Tissue Engineering and Regenerative Medicine. - : Hindawi Limited. - 1932-6254 .- 1932-7005. ; 1:2, s. 110-119
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Tidskriftsartikel (refereegranskat)abstract
- We propose that the mechanical property of the interface between an implant and its surrounding tissues is critical for the host response and the performance of the device. The interfacial mechanics depends on several different factors related to the physical shape of the device and its surface as well as properties of the host tissue and the loading conditions of the device and surrounding tissue. It seems plausible that the growth of the fibrotic tissue to support mechanical loads is governed by the same priniciples as depicted by Wolfs' Law for bone. Of course, biocompatibility will have different implications depending on which vantage point we look at the host-material interface. Another implication is that only limited aspects of biocompatibility is measurable with current in vitro tests and that the elicited host response in vivo models remains crucial for evaluation of medical devices and tissue engineering constructs.
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| 7. |
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| 8. |
- Sahlin, Herman, et al.
(författare)
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Anti-inflammatory properties of micropatterned titanium coatings
- 2006
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Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1552-4965 .- 1549-3296. ; 77A:1, s. 43-49
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Tidskriftsartikel (refereegranskat)abstract
- Prolonged inflammation and reactive oxygen species (ROS) generated around an implanted biosensor are the primary causes of the foreign body response, including encapsulation of biosensor membranes. We have previously demonstrated that TiO2 surfaces reduce ROS. Here we investigated the potential of using the anti-inflammatory properties of TiO2 in the design of biosensor membranes with improved long-term in vivo transport properties. Micropatterned Ti films were sputtered onto quartz surfaces in a series of hexagonally distributed dots with identical coverage area of 23% and dot size ranging from 5 to 100 microm. The antioxidant effect of the surfaces was investigated using a cell-free peroxynitrite donor assay and assays of superoxide released from stimulated surface-adhering neutrophils and macrophages. In all three assays, the amount of ROS was monitored using luminol-amplified chemiluminescence. Patterned surfaces in all experimental models significantly decreased ROS compared to the etched surfaces. In the cell-free experiment, the ROS reduction was only dependent on fractional surface coverage. In the cell experiments, however, a dot-size-dependent ROS reduction was seen, with the largest reduction at the smallest dot-size surfaces. These results indicate that micropatterned surfaces with small dots covering only 23% of the surface area exhibit similar antioxidative effect as fully covered surfaces.
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| 9. |
- Stevens, H Y, et al.
(författare)
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COX-2 is necessary for venous ligation-mediated bone adaptation in mice
- 2006
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Ingår i: Bone. - : Elsevier BV. - 1873-2763 .- 8756-3282. ; 38:1, s. 93-104
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Tidskriftsartikel (refereegranskat)abstract
- In osteoblasts, cyclooxygenase 2 (COX-2) is the major isozyme responsible for production of prostaglandins. Prostaglandins are local mediators of bone resorption and formation and are known to be involved in bone's adaptive response to fluid shear stress (FSS). We have previously described a model of trabecular bone loss in hindlimb-suspended mice and rats and demonstrated partial protection from osteopenia by ligation of the femoral vein. The increased FSS resulting from this ligation drove bone adaptation in the absence of mechanical loading. In this study, we investigated the role of COX-2 in this adaptive response to FSS by use of COX-2 knockout mice. COX-2 knockout ("KO"), COX-2 heterozygote ("HET"), and COX-2 wild-type ("WT") animals all lost comparable amounts of trabecular bone from sham-operated limbs as a result of suspension. In WT mice, loss of trabecular BMD in the venous-ligated limb was significantly less than that of the sham-operated limb; this effect, however, was not seen in KO or HET mice. Percentage gain in femoral periosteal circumference was greater in the ligated limb than the sham-operated limb for WT mice. KO and HET mice already possess femora of larger periosteal circumference than their WT littermates and ligation in these bones did not result in an increase in perimeter relative to sham. Histomorphometry on embedded bones revealed thinner cortices and less mineralizing perimeter in KO femora than controls. In conclusion, this is the first in vivo study to show that fluid-flow-mediated bone adaptation, independent of mechanical strain, is COX-2 dependent.
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| 10. |
- Tymchenko, Nina, 1977, et al.
(författare)
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A novel cell force sensor for quantification of traction during cell spreading and contact guidance
- 2007
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Ingår i: Biophysical Journal. - : Elsevier BV. - 1542-0086 .- 0006-3495. ; 93, s. 335-345
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we present a ridged, microfabricated, force sensor that can be used to investigate mechanical interactions between cells exhibiting contact guidance and the underlying cell culture substrate, and a proof-of-function evaluation of the force sensor performance. The substrates contain arrays of vertical pillars between solid ridges that were microfabricated in silicon wafers using photolithography and deep reactive ion etching. The spring constant of the pillars was measured by atomic force microscopy. For time-lapse experiments, cells were seeded on the pillared substrates and cultured in an on-stage incubator on a microscope equipped with re. flected differential interference contrast optics. Endothelial cells (ECs) and. broblasts were observed during attachment, spreading, and migration. Custom image analysis software was developed to resolve cell borders, cell alignment to the pillars and migration, displacements of individual pillars, and to quantify cell traction forces. Contact guidance classifi. cation was based on cell alignment and movement angles with respect to microfabricated ridges, as well as cell elongation. In initial investigations made with the ridged cell force sensor, we have observed contact guidance in ECs but not in. broblast cells. A difference in maximal amplitude of mechanical forces was observed between a contact-guided and non-contact-guided, but mobile, EC. However, further experiments are required to determine the statistical significance of this observation. By chance, we observed another feature of cell behavior, namely a reversion of cell force direction. The direction of forces measured under rounded. broblast cells changed from outwards during early cell attachment to inwards during further observation of the spreading phase. The range of forces measured under. broblasts (up to 138 nN) was greater than that measured in EC (up to 57 nN), showing that the rigid silicon sensor is capable of resolving a large range of forces, and hence detection of differences in traction forces between cell types. These observations indicate proof-of-function of the ridged cell force sensor to induce contact guidance, and that the pillared cell force sensor constructed in rigid silicon has the necessary sensitivity to detect differences in traction force vectors between different cell phenotypes and morphologies.
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