| 1. |
- Andersson, Marcus, 1975, et al.
(författare)
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Effect of molecular mobility of polymeric implants on soft tissue reactions: An in vivo study in rats
- 2008
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Ingår i: Journal of Biomedical Materials Research Part A. - : Wiley. - 1552-4965 .- 1549-3296. ; 84A:3, s. 652-660
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Tidskriftsartikel (refereegranskat)abstract
- Although numerous different polymers are used as implants or otherwise studied for many other biotechnical applications, there is a lack of basic models that correlate polymer characteristics with foreign body reactions. This study aims at developing one such model by systematically studying surface molecular mobility of polymeric implants in soft tissues in vivo. Changing the length of the alkyl side chain of poly(alkyl methacrylates) (PAMAs), provides an interesting opportunity to study the surface molecular mobility with minimal changes of the hydrophobicity of the surface. Thus, in this study three different PAMAs, with increasingly surface mobility; poly (isobutyl methacrylate) (PIBMA), poly(butyl methacrylate) (PBMA), and poly(lauryl methacralate) (PLMA) along with pure titanium (Ti) substrates were implanted in the dorsum of Sprague-Dawley rats. Inflammatory cell recruitment, cell adhesion, and cytokine release were studied after 1, 3, and 28 days of implantation. Total number of inflammatory cells in the exudate was measured but no correlation between surface mobility and cell recruitment where found. However, the number of surface associated cells where significantly lower on the surfaces with high molecular mobility (PLMA and PBMA). The histological evaluation performed after 28 days revealed thicker fibrous capsule and a higher number of blood vessels on the low molecular mobility surface (PIBMA). After 28 days the cell activity was higher on the high molecular mobility surfaces (PLMA and PBMA) compared with PIBMA, based on the cytokine release. None of the surfaces induced any significant cell-death. On the basis of the results of this study we conclude that there is a significant difference in biological response to surfaces with different in molecular mobility. This might affect the wound healing process and the biocompatibility of biomaterials. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007 -------------------------------------------------------------------------------- Received: 13 March 2006; Revised: 15 December 2006; Accepted: 29 January 2007 Digital Object Identifier (DOI) 10.1002/jbm.a.31389 About DOI
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| 2. |
- Suska, Felicia, 1974, et al.
(författare)
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In vivo cytokine secretion and NF-kappaB activation around titanium and copper implants.
- 2005
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 26:5, s. 519-27
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Tidskriftsartikel (refereegranskat)abstract
- The early biological response at titanium (Ti), copper (Cu)-coated Ti and sham sites was evaluated in an in vivo rat model. Material surface chemical and topographical properties were characterized using Auger electron spectroscopy, energy dispersive X-ray spectroscopy and interferometry, respectively. The number of leukocytes, cell types and cell viability (release of lactate dehydrogenase) were determined in the implant-interface exudate. The contents of activated nuclear transcription factor NF-kappaB, interleukin-6 (IL-6) and interleukin-10 (IL-10) were determined by enzyme linked immunosorbent assay. An increase in the number of leukocytes, in particular, polymorphonuclear leukocytes, was observed between 12 and 48 h around Cu. A marked decrease of exudate cell viability was found around Cu after 48 h. The total amounts of activated NF-kappaB after 12 h was highest in Ti exudates whereas after 48 h the highest amount of NF-kappaB was detected around Cu. The levels of cytokine IL-6 were consistently high around Cu at both time periods. No differences in IL-10 contents were detected, irrespective of material/sham and time. The results show that materials with different toxicity grades (titanium with low and copper with high toxicity) exhibit early differences in the activation of NF-kappaB, extracellular expression and secretion of mediators, causing major differences in inflammatory cell accumulation and death in vivo.
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| 3. |
- Shah, Furqan A., et al.
(författare)
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Long-term osseointegration of 3D printed CoCr constructs with an interconnected open-pore architecture prepared by electron beam melting.
- 2016
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Ingår i: Acta Biomaterialia. - : Elsevier BV. - 1878-7568 .- 1742-7061. ; 36:May, s. 296-309
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Tidskriftsartikel (refereegranskat)abstract
- In orthopaedic surgery, cobalt chromium (CoCr) based alloys are used extensively for their high strength and wear properties, but with concerns over stress shielding and bone resorption due to the high stiffness of CoCr. The structural stiffness, principally related to the bulk and the elastic modulus of the material, may be lowered by appropriate design modifications, to reduce the stiffness mismatch between metal/alloy implants and the adjacent bone. Here, 3D printed CoCr and Ti6Al4V implants of similar macro-geometry and interconnected open-pore architecture prepared by electron beam melting (EBM) were evaluated following 26week implantation in adult sheep femora. Despite higher total bone-implant contact for Ti6Al4V (39±4%) than CoCr (27±4%), bone formation patterns were similar, e.g., densification around the implant, and gradual ingrowth into the porous network, with more bone in the outer half (periphery) than the inner half (centre). Raman spectroscopy revealed no major differences in mineral crystallinity, the apatite-to-collagen ratio, or the carbonate-to-phosphate ratio. Energy dispersive X-ray spectroscopy showed similar Ca/P ratio of the interfacial tissue adjacent to both materials. Osteocytes made direct contact with CoCr and Ti6Al4V. While osteocyte density and distribution in the new-formed bone were largely similar for the two alloys, higher osteocyte density was observed at the periphery of the porous network for CoCr, attributable to slower remodelling and a different biomechanical environment. The results demonstrate the possibility to achieve bone ingrowth into open-pore CoCr constructs, and attest to the potential for fabricating customised osseointegrated CoCr implants for load-bearing applications.
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| 4. |
- Palmquist, Anders, 1977, et al.
(författare)
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A technique for evaluating bone ingrowth into 3D printed, porous Ti6Al4V implants accurately using X-ray micro-computed tomography and histomorphometry.
- 2017
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Ingår i: Micron. - : Elsevier BV. - 0968-4328. ; 94, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the application of X-ray micro-computed tomography (micro-CT) to accurately evaluate bone formation within 3D printed, porous Ti6Al4V implants manufactured using Electron Beam Melting (EBM), retrieved after six months of healing in sheep femur and tibia. All samples were scanned twice (i.e., before and after resin embedding), using fast, low-resolution scans (Skyscan 1172; Bruker micro-CT, Kontich, Belgium), and were analysed by 2D and 3D morphometry. The main questions posed were: (i) Can low resolution, fast scans provide morphometric data of bone formed inside (and around) metal implants with a complex, open-pore architecture?, (ii) Can micro-CT be used to accurately quantify both the bone area (BA) and bone-implant contact (BIC)?, (iii) What degree of error is introduced in the quantitative data by varying the threshold values?, and (iv) Does resin embedding influence the accuracy of the analysis? To validate the accuracy of micro-CT measurements, each data set was correlated with a corresponding centrally cut histological section. The results show that quantitative histomorphometry corresponds strongly with 3D measurements made by micro-CT, where a high correlation exists between the two techniques for bone area/volume measurements around and inside the porous network. On the contrary, the direct bone-implant contact is challenging to estimate accurately or reproducibly. Large errors may be introduced in micro-CT measurements when segmentation is performed without calibrating the data set against a corresponding histological section. Generally, the bone area measurement is strongly influenced by the lower threshold limit, while the upper threshold limit has little or no effect. Resin embedding does not compromise the accuracy of micro-CT measurements, although there is a change in the contrast distributions and optimisation of the threshold ranges is required.
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| 5. |
- Suska, Felicia, 1974, et al.
(författare)
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Fibrous capsule formation around titanium and copper.
- 2008
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Ingår i: Journal of Biomedical Materials Research Part A. - : Wiley. - 1549-3296 .- 1552-4965 .- 0021-9304 .- 1097-4636. ; 85:4, s. 888-96
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies suggest that implant material properties influence the quality and quantity of fibrous capsule around the implant. However, the precise relation between material surface chemistry, early inflammatory response, and fibrous subsequent repair outcome is still unknown. Titanium (Ti) and copper (Cu), surfaces with different inflammatory potential, were implanted subcutaneously in rats and retrieved fibrous capsules were analyzed after 28 and 56 days. Histological examinations show pronounced differences in capsule morphology. The fibrous capsule around Ti was thinner than that around Cu, with less number of the inflammatory cells in the layer close to the implant surface, and less and smaller blood vessels. The capsule around Cu was thick, with a large number of the inflammatory cells, particularly macrophages and giant cells, and increased number of blood vessels. Our study suggests that material surface properties, which initiate early, multiple cellular inflammatory events, are also associated with increased fibrosis and angiogenesis during repair phase. (c) 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007.
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| 6. |
- Suska, Felicia, 1974, et al.
(författare)
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Monocyte viability on titanium and copper coated titanium.
- 2005
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 26:30, s. 5942-50
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Tidskriftsartikel (refereegranskat)abstract
- The role of apoptosis/cell death in the inflammatory response at the implanted materials is unexplored. Two surfaces with different cytotoxic potential and in vivo outcomes, titanium (Ti) and copper (Cu) were incubated in vitro with human monocytes and studied using a method to discriminate apoptotic and necrotic cells (Annexin V/PI staining). Further, staurosporine, a potent inducer of apoptosis, was added to the surface adherent monocytes. Lactate dehydrogenase (a marker of cell membrane injury) and TNF-alpha and IL-10, cytokines, previously suggested to play a major role in the monocyte apoptosis, were assayed in the culture medium. The results demonstrated that Ti surfaces displayed enhanced monocyte survival and production of IL-10 and TNF-alpha. Cu adherent cells exhibited apoptotic signs as early as 1h after incubation. In contrast to Ti, after 48 h the predominance of apoptotic cells switched to apoptotic/necrotic cells on Cu surfaces. Staurosporine treatment of Ti adherent cells mediated similar type of cell death. LDH and cytokine contents were low around Cu surfaces, partly explained by interference between Cu ions and LDH and cytokines. This study suggests that material properties rapidly influence the onset of human monocyte apoptosis and progression to late apoptosis/necrosis. Early detection of apoptosis and cell death may be important for the understanding of the biological response to implanted materials.
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| 7. |
- Omar, Omar, et al.
(författare)
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Integrin and chemokine receptor gene expression in implant-adherent cells during early osseointegration.
- 2010
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Ingår i: Journal of materials science. Materials in medicine. - : Springer Science and Business Media LLC. - 1573-4838 .- 0957-4530. ; 21:3, s. 969-80
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms of early cellular recruitment and interaction to titanium implants are not well understood. The aim of this study was to investigate the expression of pro-inflammatory cytokines, chemokines and adhesion markers during the first 24 h of implantation. Anodically oxidized and machined titanium implants were inserted in rat tibia. After 3, 12, and 24 h the implants were unscrewed and analyzed with quantitative polymerase chain reaction. Immunohistochemistry and scanning electron microscopy revealed different cell types, morphology and adhesion at the two implant surfaces. A greater amount of cells, as indicated by higher expression of small subunit ribosomal RNA (18S), was detected on the oxidized surface. Higher expression of CXC chemokine receptor-4 (at 12 h) and integrins, alphav (at 12 h), beta1 (at 24 h) and beta2 (at 12 and 24 h) was detected at the oxidized surfaces. Significantly higher tumor necrosis factor-alpha (at 3 h) and interleukin-1beta (at 24 h) expression was demonstrated for the machined surface. It is concluded that material surface properties rapidly modulate the expression of receptors important for the recruitment and adhesion of cells which are crucial for the inflammatory and regenerative processes at implant surfaces in vivo.
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| 8. |
- Wermelin, Karin, 1977-, et al.
(författare)
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Stainless steel screws coated with bisphosphonates gave stronger fixation and more surrounding bone. Histomorphometry in rats.
- 2008
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Ingår i: Bone. - : Elsevier BV. - 8756-3282 .- 1873-2763. ; 42:2, s. 365-71
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Tidskriftsartikel (refereegranskat)abstract
- Coating of stainless steel screws with bisphosphonate in a fibrinogen matrix leads to an enhancement of the pullout strength 2 weeks after insertion in rat tibiae. This effect then increases over time until at least 8 weeks. The pullout force reflects the mechanical properties of the bone within the threads, which acts as a screw nut. The aim of the present study was to find descriptive and morphometric histological correlates to the increased pullout strength. Because the bisphosphonates are applied via the implant surface, we also measured bone to implant contact and how far away from the surface any effects could be seen. Stainless steel screws underwent one of three treatments: uncoated control, controls coated with a layer of cross-linked fibrinogen, or screws further modified with bisphosphonates covalently linked and physically adsorbed to the fibrinogen layer. At 1 (n=33) and 8 (n=27) weeks, bone to implant contact and bone area density in the threads were measured, as well as bone area density at 250 and 500 microm from the outer edge of the threads. Additionally, removal torque for each screw treatment was measured at 2 weeks (n=28). At 8 weeks, the part of the bisphosphonate screw that was located in the marrow cavity had become surrounded with bone, whereas there was almost no bone surrounding the controls. The bone area density in the threads along the entire bisphosphonate screw was increased by 40% compared with uncoated controls, and at 250 microm distance it was more than doubled. At 1 week, coated screws had less implant-bone contact, but at 8 weeks there was no difference between uncoated and bisphosphonate-coated screws. The bisphosphonate screws had 50% increased removal torque at 2 weeks compared to uncoated screws. Howship's lacunae and osteoclasts were found near the screws with bisphosphonates at 8 weeks, suggesting that some bone remodeling took place near the implant, in spite of the presence of bisphosphonates.
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