| 1. |
- Jing, Yujia, 1985
(författare)
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Hyperthermia-responsive liposomal systems
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Abstract Sophisticated liposomal systems are emerging at an increasing rate to meet the demands for multifunctional drug carriers in chemotherapies in combined with hyperthermia. For example, liposomal drug carriers for temperature-controlled drug release under hyperthermic conditions have recently been tested in clinical trials. More advanced designs of liposomes are expected to release encapsulated contents and activate hidden surface-functions in response to heat stimulus. Towards this aim, the present thesis is focused on formulating asymmetric lipid systems that can preserve functional moieties, and reactivate the targeted function as well as release the encapsulated compounds upon local heating. The design of the asymmetric liposomal systems utilizes the heat-activated transmembrane lipid diffusion during gel to liquid-crystalline phase transitions of the lipid membranes.Rational design of advanced liposomal drug-delivery systems will require understanding of the physicochemical properties of lipid membranes under, e.g., hyperthermic conditions. Here, supported lipid membranes on planar solid surfaces were used for model studies of lipid composition yielding a gel to liquid crystalline phase-transition temperature in the range 40 – 45 °C. It was found that the liposome-to-membrane formation process is not only size-dependent but also governed by temperature. Two methods of preparing supported asymmetric lipid membranes were investigated. As a proof-of-concept, the upper leaflets were either replaced or chemically transformed by enzymatic hydrolysis. The processes were monitored using surface sensitive techniques such as quartz crystal microbalance with dissipation (QCM-D) and dual polarization interferometry (DPI). The asymmetric structures were stable at a room temperature, while lipid flip-flop was induced upon increasing of the temperature. Transmembrane lipid exchange in the asymmetric structure under hyperthermic conditions was demonstrated by detecting, through streptavidin binding, biotinylated lipids appearing at the top leaflet which were first located in the lower leaflet. The protocols developed for the supported lipid systems were adapted for the preparation of asymmetric liposomes. Biotinylated asymmetric liposomes were used as a model system to demonstrate the principle of heat-activated targeting of asymmetric liposomes to streptavidin-coated surfaces. More biologically relevant interaction was utilized to replace the biotin-streptavidin function, where asymmetric cationic liposomes were binding to anionic supported membrane immobilized surfaces upon heating. The described strategies for assembly of asymmetric supported membranes provide a guide to the development of multifunctional drug carriers. The protocols used in experiments with supported membranes were readily adapted to the preparation of asymmetric liposomes. The ongoing study tests the asymmetric liposomes in vitro, which is designed to demonstrate hyperthermia treatment can enhance accumulation of liposomes in FaDu cells, and at the same time activate release of the encapsulated components. The results of in vitro tests can be used to analyze the feasibility of utilizing the asymmetric liposomes as a platform in vivo to explore further improvement in their functions upon microwave hyperthermia.
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| 2. |
- Orru, Anna Maria, 1976, et al.
(författare)
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AHA! festival 2015
- 2015
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The AHA festival investigates the borders between art and science in a three-day event at the Chalmers University of Technology hosted by the Department of Architecture. An international festival intended to provide enlightening experiences, staging surprises, new thoughts and displaced perspectives that lead to alternative modes of thinking about the space between art and science. We invite scientists (physicists, historians, mathematicians, medical students), artists (dancers, musicians, painters, poets, chefs) and not least architects, who reside in these borderlands and wish to share their vision and work. The key intention is to celebrate both art and science as key knowledge building devices.
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| 3. |
- Apelgren, Peter, et al.
(författare)
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Chondrocytes and stem cells in 3D-bioprinted structures create human cartilage in vivo.
- 2017
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 12:12
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Tidskriftsartikel (refereegranskat)abstract
- Cartilage repair and replacement is a major challenge in plastic reconstructive surgery. The development of a process capable of creating a patient-specific cartilage framework would be a major breakthrough. Here, we described methods for creating human cartilage in vivo and quantitatively assessing the proliferative capacity and cartilage-formation ability in mono- and co-cultures of human chondrocytes and human mesenchymal stem cells in a three-dimensional (3D)-bioprinted hydrogel scaffold. The 3D-bioprinted constructs (5 × 5 × 1.2 mm) were produced using nanofibrillated cellulose and alginate in combination with human chondrocytes and human mesenchymal stem cells using a 3D-extrusion bioprinter. Immediately following bioprinting, the constructs were implanted subcutaneously on the back of 48 nude mice and explanted after 30 and 60 days, respectively, for morphological and immunohistochemical examination. During explantation, the constructs were easy to handle, and the majority had retained their macroscopic grid appearance. Constructs consisting of human nasal chondrocytes showed good proliferation ability, with 17.2% of the surface areas covered with proliferating chondrocytes after 60 days. In constructs comprising a mixture of chondrocytes and stem cells, an additional proliferative effect was observed involving chondrocyte production of glycosaminoglycans and type 2 collagen. This clinically highly relevant study revealed 3D bioprinting as a promising technology for the creation of human cartilage.
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| 4. |
- Sukhovey, Yurij G., et al.
(författare)
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Difference between the biologic and chronologic age as an individualized indicator for the skin care intensity selection : skin topography and immune system state studies, parameter correlations with age difference
- 2019
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Ingår i: Biomedical Dermatology. - : Springer Nature. - 2398-8460. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- Background: Present research addresses the issue of skin aging and corresponding skin treatment individualization. Particular research question was on the developing of simplified criterion supporting patient-specific decision on the necessity and intensity of skin treatment. Basing on the published results and a wide pool of experimental data, we have formulated a hypothesis that a difference between biologic and chronologic age can be used as an express criterion of skin aging.Methods: In present paper, we report the results of studies with 80 volunteers between 15 and 65 years of age, linking parameters reflecting immune state, skin state, and topography to the difference between biologic and chronologic age. Facial skin topography, skin moisture, sebum level, and skin elasticity were studied using commercial devices. Blood immunology studies were performed using venous blood samples. Correlations between all measured parameters and age difference were calculated. Also, cross correlations between skin cell profile and blood immune profile parameters, and skin roughness parameters were calculated.Results: Age dependencies of the blood immunological parameters on the biologic and chronologic age difference are less pronounced as compared to the changes in skin cell profile parameters. However, the changes in the tendencies when biologic age becomes equal to chronologic one are visible for all studied parameters.All measured skin roughness parameters show correlations with age difference, but average skin roughness and depth of the deepest profile valley have the largest correlation coefficient values. Many of the measured skin cell profile and blood immunology parameters show strong correlations with average skin roughness and deepest profile valley, with some of the coefficients exceeding 0.5–0.6.Conclusions: Basing on own experiments and published research results, it is possible to suggest using the difference between calculated biologic age and chronologic age as an individualized criterion supporting decisions on skin treatment strategy. Further research involving larger numbers of participants and aiming on optimizing the expressions for calculating biologic age could lead to reliable and easily available express criterion supporting the decision making for an individualized skin treatment.
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| 5. |
- Karlsson, Johan, 1984, et al.
(författare)
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Stem cell homing using local delivery of plerixafor and stromal derived growth factor-1alpha for improved bone regeneration around Ti-implants
- 2016
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Ingår i: Journal of Biomedical Materials Research - Part A. - : Wiley. - 1552-4965 .- 1549-3296. ; 104:10, s. 2466-2475
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Tidskriftsartikel (refereegranskat)abstract
- Triggering of the early healing events, including the recruitment of progenitor cells, has been suggested to promote bone regeneration. In implantology, local drug release technologies could provide an attractive approach to promote tissue regeneration. In this study, we targeted the chemotactic SDF-1a/CXCR4 axis that is responsible e.g. for the homing of stem cells to trauma sites. This was achieved by local delivery of plerixafor, an antagonist to CXCR4, and/or SDF-1a from titanium implants coated with mesoporous titania thin films with a pore size of 7.5 nm. In vitro drug delivery experiments demonstrated that the mesoporous coating provided a high drug loading capacity and controlled release. The subsequent in vivo study in rat tibia showed beneficial effects with respect to bone-implant anchorage and bone-formation along the surface of the implants when plerixafor and SDF-1a were delivered locally. The effect was most prominent by the finding that the combination of the drugs significantly improved the mechanical bone anchorage. These observations suggest that titanium implants with local delivery of drugs for enhanced local recruitment of progenitor cells have the ability to promote osseointegration. This approach may provide a potential strategy for the development of novel implant treatments.
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| 6. |
- Andersson, Marlene, et al.
(författare)
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Biomimetic spinning of artificial spider silk from a chimeric minispidroin
- 2017
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Ingår i: Nature Chemical Biology. - : Springer Science and Business Media LLC. - 1552-4450 .- 1552-4469. ; 254
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Tidskriftsartikel (refereegranskat)abstract
- Herein we present a chimeric recombinant spider silk protein (spidroin) whose aqueous solubility equals that of native spider silk dope and a spinning device that is based solely on aqueous buffers, shear forces and lowered pH. The process recapitulates the complex molecular mechanisms that dictate native spider silk spinning and is highly efficient; spidroin from one liter of bacterial shake-flask culture is enough to spin a kilometer of the hitherto toughest as-spun artificial spider silk fiber.
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| 7. |
- Apelgren, Peter, et al.
(författare)
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In Vivo Human Cartilage Formation in Three-Dimensional Bioprinted Constructs with a Novel Bacterial Nanocellulose Bioink
- 2019
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Ingår i: Acs Biomaterials Science & Engineering. - : American Chemical Society (ACS). - 2373-9878. ; 5:5, s. 2482-2490
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial nanocellulose (BNC) is a 3D network of nanofibrils exhibiting excellent biocompatibility. Here, we present the aqueous counter collision (ACC) method of BNC disassembly to create bioink with suitable properties for cartilage-specific 3D-bioprinting. BNC was disentangled by ACC, and fibril characteristics were analyzed. Bioink printing fidelity and shear-thinning properties were evaluated. Cell-laden bioprinted grid constructs (5 X 5 X 1 mm(3)) containing human nasal chondrocytes (10 M mL(-1)) were implanted in nude mice and explanted after 30 and 60 days. Both ACC and hydrolysis resulted in significantly reduced fiber lengths, with ACC resulting in longer fibrils and fewer negative charges relative to hydrolysis. Moreover, ACC-BNC bioink showed outstanding printability, postprinting mechanical stability, and structural integrity. In vivo, cell-laden structures were rapidly integrated, maintained structural integrity, and showed chondrocyte proliferation, with 32.8 +/- 13.8 cells per mm(2) observed after 30 days and 85.6 +/- 30.0 cells per mm(2) at day 60 (p = 0.002). Furthermore, a full-thickness skin graft was attached and integrated completely on top of the 3D-bioprinted construct. The novel ACC disentanglement technique makes BNC biomaterial highly suitable for 3D-bioprinting and clinical translation, suggesting cell-laden 3D-bioprinted ACC-BNC as a promising solution for cartilage repair.
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| 8. |
- Asif, Sana, et al.
(författare)
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Heparinization of cell surfaces with short peptide-conjugated PEG-lipid regulates thromboinflammation in transplantation of human MSCs and hepatocytes
- 2016
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Ingår i: Acta Biomaterialia. - : Elsevier BV. - 1742-7061 .- 1878-7568. ; 35, s. 194-205
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Tidskriftsartikel (refereegranskat)abstract
- Infusion of therapeutic cells into humans is associated with immune responses, including thromboinflammation, which result in a large loss of transplanted cells\ To address these problems, heparinization of the cell surfaces was achieved by a cell-surface modification technique using polyethylene glycol conjugated phospholipid (PEG-lipid) derivatives. A short heparin-binding peptide was conjugated to the PEG-lipid for immobilization of heparin conjugates on the surface of human mesenchymal stem cells (hMSCs) and human hepatocytes. Here three kinds of heparin-binding peptides were used for immobilizing heparin conjugates and examined for the antithrombogenic effects on the cell surface. The heparinized cells were incubated in human whole blood to evaluate their hemocompatibility by measuring blood parameters such as platelet count, coagulation markers, complement markers, and Factor Xa activity. We found that one of the heparin-binding peptides did not show cytotoxicity after the immobilization with heparin conjugates. The degree of binding of the heparin conjugates on the cell surface (analyzed by flow cytometer) depended on the ratio of the active peptide to control peptide. For both human MSCs and hepatocytes in whole-blood experiments, no platelet aggregation was seen in the heparin conjugate-immobilized cell group vs. the controls (non-coated cells or control peptide). Also, the levels of thrombin-antithrombin complex (TAT), C3a, and sC5b-9 were significantly lower than those of the controls, indicating a lower activation of coagulation and complement. Factor Xa analysis indicated that the heparin conjugate was still active on the cell surface at 24 h post-coating. It is possible to immobilize heparin conjugates onto hMSC and human hepatocyte surfaces and thereby protect the cell surfaces from damaging thromboinflammation. Statement of Signigficance We present a promising approach to enhance the biocompatibility of therapeutic cells. Here we used short peptide-conjugated PEG-lipid for cell surface modification and heparin conjugates for the coating of human hepatocytes and MSCs. We screened the short peptides to find higher affinity for heparinization of cell surface and performed hemocompatibility assay of heparinized human hepatocytes and human MSCs in human whole blood. Using heparin-binding peptide with higher affinity, not only coagulation activation but also complement activation was significantly suppressed. Thus, it was possible to protect human hepatocytes and human MSCs from the attack of thromboinflammatory activation, which can contribute to the improvement graft survival. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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| 9. |
- Asif, Sana, M.D, PhD student, et al.
(författare)
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Validation of an MPC polymer coating to attenuate surface- induced cross-talk between the complement and coagulation systems in whole blood in in vitro and in vivo models
- 2019
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Ingår i: Macromolecular Bioscience. - : Wiley-VCH Verlagsgesellschaft. - 1616-5187 .- 1616-5195. ; 19:5
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Tidskriftsartikel (refereegranskat)abstract
- Artificial surfaces that come into contact with blood induce an immediate activation of the cascade systems of the blood, leading to a thrombotic and/or inflammatory response that can eventually cause damage to the biomaterial or the patient, or to both. Heparin coating has been used to improve hemocompatibility, and another approach is 2-methacryloyloxyethyl phosphorylcholine (MPC)-based polymer coatings. Here, the aim is to evaluate the hemocompatibility of MPC polymer coating by studying the interactions with coagulation and complement systems using human blood in vitro model and pig in vivo model. The stability of the coatings is investigated in vitro and MPC polymer-coated catheters are tested in vivo by insertion into the external jugular vein of pigs to monitor the catheters' antithrombotic properties. There is no significant activation of platelets or of the coagulation and complement systems in the MPC polymer-coated one, which was superior in hemocompatibility to non-coated matrix surfaces. The protective effect of the MPC polymer coat does not decline after incubation in human plasma for up to 2 weeks. With MPC polymer-coated catheters, it is possible to easily draw blood from pig for 4 days in contrast to the case for non-coated catheters, in which substantial clotting is seen.
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| 10. |
- Barreto Henriksson, Helena, et al.
(författare)
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Determination of mechanical and rheological properties of a cell-loaded peptide gel during ECM production
- 2019
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Ingår i: International Journal of Pharmaceutics. - : Elsevier BV. - 0378-5173 .- 1873-3476. ; 563, s. 437-444
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Tidskriftsartikel (refereegranskat)abstract
- The development of an injectable biomaterial that supports cell survival and maintains or promotes nucleus pulposus (NP) phenotype could aid delivery of cells to degenerated NPs causing low back pain. Mesenchymal cells were loaded and grown in a synthetic peptide gel, PuraMatrix (R). Cells were observed within the gels over 0-28 days, and accumulation of glycosaminoglycans were detected by histological staining. The mechanical properties of the cell-loaded constructs, and the change of the mechanical properties were studied using stress relaxation of the gels under compression and confinement. The PuraMatrix (R) gel was shown to relax fast on compression indicating that the fluid could easily flow out of the gel, and thus indicating the presence of large pores/voids. The presence of these pores/voids was further supported by high mobility of dextran molecules, determined using fluorescence recovery after photo bleaching. The stress required to deform the cell-loaded constructs to a specific strain increases at day 21, at which point the presence of glycosaminoglycans within the cell-loaded constructs was also observed. The results provide evidence of changes in mechanical properties of the PuraMatrix (R) matrix upon excretion of the extracellular matrix by the cells.
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| 11. |
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| 12. |
- Fursatz, Marian, et al.
(författare)
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Functionalization of bacterial cellulose wound dressings with the antimicrobial peptide ε-poly-L-Lysine
- 2018
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Ingår i: Biomedical Materials. - : Institute of Physics Publishing (IOPP). - 1748-6041 .- 1748-605X. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Wound dressings based on bacterial cellulose (BC) can form a soft and conformable protective layer that can stimulate wound healing while preventing bacteria from entering the wound. Bacteria already present in the wound can, however, thrive in the moist environment created by the BC dressing which can aggravate the healing process. Possibilities to render the BC antimicrobial without affecting the beneficial structural and mechanical properties of the material would hence be highly attractive. Here we present methods for functionalization of BC with ε-Poly-L-Lysine (ε-PLL), a non-toxic biopolymer with broad-spectrum antimicrobial activity. Low molecular weight ε-PLL was cross-linked in pristine BC membranes and to carboxymethyl cellulose (CMC) functionalized BC using carbodiimide chemistry. The functionalization of BC with ε-PLL inhibited growth of S. epidermidis on the membranes but did not affect the cytocompatibility to cultured human fibroblasts as compared to native BC. The functionalization had no significant effects on the nanofibrous structure and mechanical properties of the BC. The possibility to functionalize BC with ε-PLL is a promising, green and versatile approach to improve the performance of BC in wound care and other biomedical applications.
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| 13. |
- Georgiou, Melanie, et al.
(författare)
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Engineered neural tissue with aligned, differentiated adipose-derived stem cells promotes peripheral nerve regeneration across a critical sized defect in rat sciatic nerve
- 2015
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 37, s. 242-251
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Tidskriftsartikel (refereegranskat)abstract
- Adipose-derived stem cells were isolated from rats and differentiated to a Schwann cell-like phenotype in vitro. The differentiated cells (dADSCs) underwent self-alignment in a tethered type-1 collagen gel, followed by stabilisation to generate engineered neural tissue (EngNT-dADSC). The pro-regenerative phenotype of dADSCs was enhanced by this process, and the columns of aligned dADSCs in the aligned collagen matrix supported and guided neurite extension in vitro. EngNT-dADSC sheets were rolled to form peripheral nerve repair constructs that were implanted within NeuraWrap conduits to bridge a 15 mm gap in rat sciatic nerve. After 8 weeks regeneration was assessed using immunofluorescence imaging and transmission electron microscopy and compared to empty conduit and nerve graft controls. The proportion of axons detected in the distal stump was 3.5 fold greater in constructs containing EngNT-dADSC than empty tube controls. Our novel combination of technologies that can organise autologous therapeutic cells-within an artificial tissue construct provides a promising new cellular biomaterial for peripheral nerve repair.
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| 14. |
- Halling Linder, Cecilia, 1975-
(författare)
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Biochemical and functional properties of mammalian bone alkaline phosphatase isoforms during osteogenesis
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The human skeleton is a living and dynamic tissue that constantly is being renewed in a process called bone remodeling. Old bone is resorbed by osteoclasts and new bone is formed by osteoblasts. Bone is a composite material made up by mineral crystals in the form of hydroxyapatite (calcium and phosphate) that provides the hardness of bone, and collagen fibrils that provides elasticity and flexibility. Alkaline phosphatase (ALP) is a family of enzymes that is present in most species and catalyzes the hydrolysis of various phosphomonoesters at alkaline pH. Despite the generalized use of ALP as a biochemical marker of bone formation, the precise function of bone ALP (BALP) is only now becoming clear. Three circulating human BALP isoforms (B1, B2, and B/I) can be distinguished in healthy individuals and a fourth isoform (B1x) has been discovered in patients with chronic kidney disease and in bone tissue.Paper I. Three endogenous phosphocompounds, (i.e., inorganic pyrophosphate (PPi), pyridoxal 5′-phosphate (PLP) and phosphoethanolamine (PEA)), have been suggested to serve as physiological substrates for BALP. The BALP isoforms display different catalytic properties towards PPi and PLP, which is attributed to their distinct N-linked glycosylation patterns. The catalytic activity, using PEA as substrate, was barely detectable for all BALP isoforms indicating that PEA is not a physiological substrate for BALP.Paper II. Mouse serum ALP is frequently measured and interpreted in mammalian bone research. However, little is known about the circulating ALPs in mice and their relation to human ALP. We characterized the circulating and tissue-derived mouse ALP isozymes and isoforms from mixed strains of wild-type and knockout mice. All four BALP isoforms (B/I, B1x, B1, and B2) were identified in mouse serum and bone tissues, in good correspondence with those found in human bones. All mouse tissues, except liver, contained significant ALP activities. This is a notable difference as human liver contains vast amounts of ALP.Paper III. The objective of this study was to investigate the binding properties of human collagen type I to human BALP, including the two BALP isoforms B1 and B2, together with ALP from human liver, human placenta and E. coli. A surface plasmon resonance-based analysis showed that BALP binds stronger to collagen type I in comparison with ALPs expressed in non-mineralizing tissues. The B2 isoform binds significantly stronger to collagen type I in comparison with the B1 isoform, indicating that glycosylation differences in human ALPs are of crucial importance for protein–protein interactions with collagen type I.Paper IV. Tartrate-resistant acid phosphatase (TRAP) is highly expressed in osteoclasts and frequently used as a marker of bone resorption. Intriguingly, recent studies show that TRAP is also expressed in osteoblasts and osteocytes. TRAP displays enzymatic activity towards the endogenous substrates for BALP, i.e., PPi and PLP. Both TRAP and BALP can alleviate the inhibitory effect of osteopontin on mineralization by dephosphorylation, which suggests a novel role for TRAP in skeletal mineralization.
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| 15. |
- Huang, Shan, et al.
(författare)
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Reciprocal relationship between contact and complement system activation on artificial polymers exposed to whole human blood.
- 2016
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Ingår i: Biomaterials. - : Elsevier. - 0142-9612 .- 1878-5905. ; 77, s. 111-119
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Inappropriate and uncontrolled activation of the cascade systems in the blood is a driving force in adverse inflammatory and thrombotic reactions elicited by biomaterials, but limited data are available on the activation of the contact system by polymers and the present study was undertaken to investigate these mechanisms in established models.METHODS: Polymer particles were incubated in (1) EDTA-plasma (10 mM) to monitor the adsorption of 20 selected proteins; (2) lepirudin-anticoagulated plasma to evaluate contact system activation, monitored by the formation of complexes between the generated proteases factor[F]XIIa, FXIa and kallikrein and the serpins C1-inhibitor [C1INH] and antithrombin [AT]; (3) lepirudin-anticoagulated whole blood to determine cytokine release.RESULTS: Strong negative correlations were found between 10 cytokines and the ratio of deposited FXII/C1INH, generated FXIIa-C1INH complexes, and kallikrein-C1INH complexes. Formation of FXIIa-C1INH complexes correlated negatively with the amount of C3a and positively with deposited IgG.CONCLUSIONS: A reciprocal relationship was found between activation of the contact system and the complement system induced by the polymers studied here. The ratios of FXII/C1INH or C4/C4BP, adsorbed from EDTA-plasma are useful surrogate markers for cytokine release and inflammatory response to materials intended for blood contact.
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| 16. |
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| 17. |
- Karlsson, Johan, 1984, et al.
(författare)
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The effect of alendronate on biomineralization at the bone/implant interface
- 2016
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Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 104:3, s. 620-629
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Tidskriftsartikel (refereegranskat)abstract
- A recent approach to improve the osseointegration of implants is to utilize local drug administration. The presence of an osteoporosis drug may influence both bone quantity and quality at the bone/implant interface. Despite this, the performance of bone-anchoring implants is traditionally evaluated only by quantitative measurements. In the present study, the osteoporosis drug alendronate (ALN) was administrated from mesoporous titania thin films that were coated onto titanium implants. The effect that the drug had on biomineralization was explored both in vitro using simulated body fluid (SBF) and in vivo in a rat tibia model. The SBF study showed that the apatite formation was completely hindered at a high concentration of ALN (0.1 mg/mL). However, when ALN was administrated from the mesoporous coating the surface became completely covered with apatite. Ex vivo characterization of the bone/implant interface using Raman spectroscopy demonstrated that the presence of ALN enhanced the bone mineralization, and that the chemical signature of newly formed bone in the presence of ALN had a higher resemblance to the pre-existing mature bone than to the bone formed without drug. Taken together, this study demonstrates the importance of evaluating the quality of the formed bone to better understand the performance of implants.
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| 18. |
- Karlsson, Johan, et al.
(författare)
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The effect of alendronate on biomineralization at the bone/implant interface.
- 2016
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Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 104:3, s. 620-629
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Tidskriftsartikel (refereegranskat)abstract
- A recent approach to improve the osseointegration of implants is to utilize local drug administration. The presence of an osteoporosis drug may influence both bone quantity and quality at the bone/implant interface. Despite this, the performance of bone-anchoring implants is traditionally evaluated only by quantitative measurements. In the present study, the osteoporosis drug alendronate (ALN) was administrated from mesoporous titania thin films that were coated onto titanium implants. The effect that the drug had on biomineralization was explored both in vitro using simulated body fluid (SBF) and in vivo in a rat tibia model. The SBF study showed that the apatite formation was completely hindered at a high concentration of ALN (0.1 mg/mL). However, when ALN was administrated from the mesoporous coating the surface became completely covered with apatite. Ex vivo characterization of the bone/implant interface using Raman spectroscopy demonstrated that the presence of ALN enhanced the bone mineralization, and that the chemical signature of newly formed bone in the presence of ALN had a higher resemblance to the pre-existing mature bone than to the bone formed without drug. Taken together, this study demonstrates the importance of evaluating the quality of the formed bone to better understand the performance of implants. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A 104A: 620-629, 2016.
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| 19. |
- Nygren, Håkan, 1952, et al.
(författare)
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Mineralization at Titanium Surfaces is a Two-Step Process.
- 2016
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Ingår i: Journal of functional biomaterials. - : MDPI AG. - 2079-4983. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- Mapping the initial reaction of implants with blood or cell culture medium is important for the understanding of the healing process in bone. In the present study, the formation of low crystalline carbonated hydroxyapatite (CHA) onto commercially pure titanium (Ti) implants from cell culture medium and blood, is described as an early event in bone healing at implants. The Ti-implants were incubated with cell culture medium (DMEM) or whole blood and the surface concentration of Ca, P and HA was analyzed by XPS, EDX and Tof-SIMS. After incubation with DMEM for 16 h and 72 h, EDX and XPS analysis showed stable levels of Ca and P on the Ti-surface. ESEM images showed an even distribution of Ca and P. Further analysis of the XPS results indicated that CHA was formed at the implants. Analysis with ToF-SIMS yielded high m.w. fragments of HA, such as Ca₂PO4 at m/z 174.9 and Ca₃PO₅ at m/z 230.8, as secondary ions at the Ti-surfaces. Analysis of implants incubated in blood for 16 h, with ToF-SIMS, showed initial formation of CHA yielding CaOH as secondary ion. The results indicate that early mineralization at Ti-surfaces is an important step in the healing of implants into bone.
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| 20. |
- Odeberg, Jacob, et al.
(författare)
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A novel cysteine-linked antibacterial surface coating significantly inhibits bacterial colonization of nasal silicone prongs in a phase one pre-clinical trial
- 2018
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Ingår i: Materials science & engineering. C, biomimetic materials, sensors and systems. - : ELSEVIER SCIENCE BV. - 0928-4931 .- 1873-0191. ; 93, s. 782-789
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Tidskriftsartikel (refereegranskat)abstract
- Ventilator associated pneumonia and sepsis are frequent complications in neonatal care. Bacterial colonization of medical devices and interfaces used for respiratory support may contribute by functioning as a bacterial reservoir seeding bacteria into airways. We have developed an antibacterial surface coating based on a cysteine ligand covalently coupled via a spacer to a carboxylic backbone layer on an acrylic acid grafted silicone surface. This coating was applied on a commercially available nasal prong and the antibacterial effect was evaluated both in vitro and in vivo in a first-in-human phase 1 trial. The coated nasal prongs had strong antibacterial activity against both Gram-negative and Gram-positive bacteria in vitro. In a randomized pre-clinical trial study of 24 + 24 healthy adult volunteers who carried coated or non-coated nasal prongs for 18 h, a (10)log difference in mean bacterial colonization of 5.82 (p < 0.0001) was observed. These results show that this coating technique can prevent colonization by the normal skin and mucosal flora, and thus represent a promising novel technology for reduction of medical device-associated hospital acquired infections.
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| 21. |
- Padma, Arvind M., et al.
(författare)
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Protocols for Rat Uterus Isolation and Decellularization: Applications for Uterus Tissue Engineering and 3D Cell Culturing.
- 2018
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Ingår i: Decellularized Scaffolds and Organogenesis. Kursad Turksen (red.). - New York, NY : Springer. - 1940-6029. - 9781493976553 ; , s. 161-175
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Bokkapitel (refereegranskat)abstract
- Sophisticated culturing conditions are required to grow cells in a three-dimensional (3D) environment. Cells then require a type of scaffold rich in proteins, growth factors, and signaling molecules that simulates their natural environment. Tissues from all species of animals have an organ-specific extracellular matrix (ECM) structure that plays a key role in cell proliferation and migration. Hence, the scaffold composition plays a significant role for any successful 3D cell culturing system. We developed a whole rat uterus ECM scaffold by the perfusion of detergents and ionic solutions through the vascular system of an isolated normal rat uterus in a process termed "decellularization." The generated rat uterus scaffolds consist of a cell-free ECM structure similar to that of the normal rat uterus, and are thus excellent platforms on to which new cells can be added. Rat uterus 3D cell culturing systems based on these scaffolds could become valuable to decidual differentiation- and embryo implantation studies, or for investigating invasion mechanisms of endometrial cancer cells. They could also be used for the creation of tissue engineered uterine tissue, for partial or whole organogenesis developed for transplantation applications to treat absolute uterine infertility. This is a condition affecting about 1 in 500 women, and is only treatable by a uterus transplantation. This article provides valuable troubleshooting notes and describes in detail how to generate rat uterus scaffolds, including the delicate surgery required to isolate the uterus with an intact vascular tree which facilitates vascular perfusion and re-transplantation.
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| 22. |
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| 23. |
- Raina, Deepak Bushan, et al.
(författare)
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A Biphasic Calcium Sulphate/Hydroxyapatite Carrier Containing Bone Morphogenic Protein-2 and Zoledronic Acid Generates Bone
- 2016
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- In orthopedic surgery, large amount of diseased or injured bone routinely needs to be replaced. Autografts are mainly used but their availability is limited. Commercially available bone substitutes allow bone ingrowth but lack the capacity to induce bone formation. Thus, off-the-shelf osteoinductive bone substitutes that can replace bone grafts are required. We tested the carrier properties of a biphasic, calcium sulphate and hydroxyapatite ceramic material, containing a combination of recombinant human bone morphogenic protein-2 (rhBMP-2) to induce bone, and zoledronic acid (ZA) to delay early resorption. In-vitro, the biphasic material released 90% of rhBMP-2 and 10% of ZA in the first week. No major changes were found in the surface structure using scanning electron microscopy (SEM) or in the mechanical properties after adding rhBMP-2 or ZA. In-vivo bone formation was studied in an abdominal muscle pouch model in rats (n = 6/group). The mineralized volume was significantly higher when the biphasic material was combined with both rhBMP-2 and ZA (21.4 ± 5.5 mm3) as compared to rhBMP-2 alone (10.9 ± 2.1 mm3) when analyzed using micro computed tomography (μ-CT) (p 0.01). In the clinical setting, the biphasic material combined with both rhBMP-2 and ZA can potentially regenerate large volumes of bone.
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| 24. |
- Shah, Furqan A., et al.
(författare)
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Bioactive glass and glass-ceramic scaffolds for bone tissue engineering
- 2018
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Ingår i: Bioactive Glasses (Second Edition). - 9780081009369 ; , s. 201-33
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Bioactive glasses and glass-ceramics are a diverse group of materials possessing a unique set of physicochemical properties that make them useful for bone repair. Scaffolds for bone tissue engineering are subject to many requirements including biocompatibility, osteogenesis, biodegradability, and mechanical competence, all of which must be considered in the design features. This chapter addresses various scaffold fabrication techniques for melt-derived and sol-gel-derived compositions, polymer-based organic-inorganic composites, calcium phosphate-based inorganic-inorganic composites, bioactive bone cements, scaffolds based on glass compositions containing specific therapeutic ions, and hybrid materials where the organic and inorganic phases interact at the molecular level. The most important achievements, challenges and potential solutions, as well as the most promising areas of future research involving bioactive glasses and glass-ceramics for bone tissue engineering are presented.
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| 25. |
- Trentin, Danielle S, et al.
(författare)
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Natural green coating inhibits adhesion of clinically important bacteria
- 2015
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 5, s. 8287-
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Tidskriftsartikel (refereegranskat)abstract
- Despite many advances, biomaterial-associated infections continue to be a major clinical problem. In order to minimize bacterial adhesion, material surface modifications are currently being investigated and natural products possess large potential for the design of innovative surface coatings. We report the bioguided phytochemical investigation of Pityrocarpa moniliformis and the characterization of tannins by mass spectrometry. It was demonstrated that B-type linked proanthocyanidins-coated surfaces, here termed Green coatings, reduced Gram-positive bacterial adhesion and supported mammalian cell spreading. The proposed mechanism of bacterial attachment inhibition is based on electrostatic repulsion, high hydrophilicity and the steric hindrance provided by the coating that blocks bacterium-substratum interactions. This work shows the applicability of a prototype Green-coated surface that aims to promote necessary mammalian tissue compatibility, while reducing bacterial colonization.
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| 26. |
- Rasmusson, Lars, 1962, et al.
(författare)
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Autogena stamceller för benrekonstruktion av defekter i käkarna
- 2018
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Ingår i: Tandläkartidningen. - 0039-6982. ; 109:11, s. 104-108
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Tidskriftsartikel (refereegranskat)abstract
- Fallbeskrivning av 2 patienter som efter misslyckad rekonstruktion av underkäken med autologa bentransplantat rekonstruerades med ben utvunnet ur stamceller från patientens egen fettvävnad. Differentiering och cellvitalitet kunde bekräftas före re-implantation. Moget ben kunde konstateras kliniskt, histologiskt och radiologiskt efter 1 år.
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| 27. |
- Shchukarev, Andrey, et al.
(författare)
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Surface characterization of insulin-coated Ti6Al4V medical implants conditioned in cell culture medium: An XPS study
- 2017
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 216, s. 33-38
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 Elsevier B.V.Surface characterization of insulin-coated Ti6Al4V medical implants, after incubation in α-minimum essential medium (α-MEM), was done by X-ray photoelectron spectroscopy (XPS), in order to analyze the insulin behavior at the implant – α-MEM interface. In the absence of serum proteins in cell culture medium, the coated insulin layer remained intact, but experienced a time-dependent structural transformation exposing hydrophobic parts of the protein toward the solution. The presence of fetal bovine serum (FBS) in the medium resulted in partial substitution of insulin by serum proteins. In spite of some insulin release, the remaining coated layer demonstrated a direct surface effect by stabilizing the structure of protein competitors, and by supporting the accumulation of calcium and phosphate ions at the interface. A structurally stable protein layer with incorporated calcium and phosphate ions at the implant–tissue interface could be an important prerequisite for enhanced bone formation.
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| 28. |
- Trbakovic, Amela, et al.
(författare)
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A new synthetic granular calcium phosphate compound induces new bone in a sinus lift rabbit model
- 2018
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Ingår i: Journal of Dentistry. - : Elsevier BV. - 0300-5712 .- 1879-176X. ; 70, s. 31-39
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Tidskriftsartikel (refereegranskat)abstract
- Objectives The aim of this study was to investigate if a synthetic granular calcium phosphate compound (CPC) and a composite bisphosphonate-linked hyaluronic acid–calcium phosphate hydrogel (HABP·CaP) induced similar or more amount of bone as bovine mineral in a modified sinus lift rabbit model. Material and methods Eighteen adult male New Zeeland White rabbits, received randomly one of the two test materials on a random side of the face, and bovine mineral as control on the contralateral side. In a sinus lift, the sinus mucosa was elevated and a titanium mini-implant was placed in the alveolar bone. Augmentation material (CPC, HABP·CaP or bovine bone) was applied in the space around the implant. The rabbits were euthanized three months after surgery and qualitative and histomorphometric evaluation were conducted. Histomorphometric evaluation included three different regions of interest (ROIs) and the bone to implant contact on each installed implant. Results Qualitative assessment (p=<.05), histomorphometric evaluations (p=<.01), and implant incorporation (p=<.05) showed that CPC and bovine mineral induced similar amount of bone and more than the HABP·CaP hydrogel. Conclusion CPC induced similar amount of bone as bovine mineral and both materials induced more bone than HABP·CaP hydrogel. Clinical significance The CPC is suggested as a synthetic alternative for augmentations in the maxillofacial area.
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| 29. |
- Alenezi, Ali, et al.
(författare)
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Osseointegration effects of local release of strontium ranelate from implant surfaces in rats
- 2019
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Ingår i: Journal of Materials Science: Materials in Medicine. - : Springer Science and Business Media LLC. - 0957-4530 .- 1573-4838. ; 30:10, s. 116-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND : Numerous studies have reported the beneficial effects of strontium on bone growth, particularly by stimulating osteoblast proliferation and differentiation. Thus, strontium release around implants has been suggested as one possible strategy to enhance implant osseointegration. AIM : This study aimed to evaluate whether the local release of strontium ranelate (Sr-ranelate) from implants coated with mesoporous titania could improve bone formation around implants in an animal model. MATERIALS AND METHODS : Mesoporous titania (MT) thin coatings were formed utilizing the evaporation induced self-assembly (EISA) method using Pluronic (P123) with or without the addition of poly propylene glycol (PPG) to create materials with two different pore sizes. The MT was deposited on disks and mini-screws, both made of cp Ti grade IV. Scanning electron microscopy (SEM) was performed to characterize the MT using a Leo Ultra55 FEG instrument (Zeiss, Oberkochen, Germany). The MT was loaded with Sr-ranelate using soaking and the drug uptake and release kinetics to and from the surfaces were evaluated using quartz crystal microbalance with dissipation monitoring (QCM-D) utilizing a Q-sense E4 instrument. For the in vivo experiment, 24 adult rats were analyzed at two time points of implant healing (2 and 6 weeks). Titanium implants shaped as mini screws were coated with MT films and divided into two groups; supplied with Sr-ranelate (test group) and without Sr-ranelate (control group). Four implants (both test and control) were inserted in the tibia of each rat. The in vivo study was evaluated using histomorphometric analyses of the implant/bone interphase using optical microscopy. RESULTS : SEM images showed the successful formation of evenly distributed MT films covering the entire surface with pore sizes of 6 and 7.2 nm, respectively. The QCM-D analysis revealed an absorption of 3300 ng/cm2 of Sr-ranelate on the 7.2 nm MT, which was about 3 times more than the observed amount on the 6 nm MT (1200 ng/cm2). Both groups showed sustained release of Sr-ranelate from MT coated disks. The histomorphometric analysis revealed no significant differences in bone implant contact (BIC) and bone area (BA) between the implants with Sr-ranelate and implants in the control groups after 2 and 6 weeks of healing (BIC with a p-value of 0.43 after 2 weeks and 0.172 after 6 weeks; BA with a p-value of 0.503 after 2 weeks, and 0.088 after 6 weeks). The mean BIC and BA values within the same group showed significant increase among all groups between 2 and 6 weeks. CONCLUSION : This study could not confirm any positive effects of Sr-ranelate on implant osseointegration.
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| 30. |
- Gatenholm, Paul, 1956, et al.
(författare)
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Effect of cultivation conditions on the structure and morphological properties of BNC biomaterials with a focus on vascular grafts
- 2016
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Ingår i: Bacterial NanoCellulose: A Sophisticated Multifunctional Material. - Boca Raton : CRC Press. - 9781439869925 ; , s. 19-42
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- 20 New materials that are not thrombogenic and have mechanical properties that mimic the native blood vessel are in very great demand. Nanocellulose produced by the bacteria Gluconacetobacter xylinus is a biomaterial that has gained interest in the field of tissue engineering because of its unique properties, such as great mechanical strength, high water content (around 99%), and the ability to be shaped into three-dimensional structures during biosynthesis. The fabrication process of bacterial nanocellulose (BNC) vascular grafts is very unique because the material synthesis and product formation takes place simultaneously. The bio mechanical performance, which includes rupture pressure and compliance along with biological response (endothelialization, blood compatibility, etc.), is dependent on the morphology of a fibrillar network. The network formation is affected by cellulose assembly and bacteria motion, proliferation rate, and other factors. An understanding of the effects of cultivation conditions on BNC network formation is therefore of great importance.
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| 31. |
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| 32. |
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| 33. |
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| 34. |
- Yang, Xianyan, et al.
(författare)
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Intra-bone marrow injection of trace elements co-doped calcium phosphate microparticles for the treatment of osteoporotic rat
- 2017
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Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 105:5, s. 1422-1432
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Tidskriftsartikel (refereegranskat)abstract
- Osteoporotic femur fractures are the most common fragility fracture and account for approximately one million injuries per year. Local intervention by intra-marrow injection is potentially a good choice for preventing osteoporotic bone loss when the osteoporotic femoral fracture was treated. Previously, it was shown that trace element co-doped calcium phosphate (teCaP) implants could stimulate osteoporotic bone marrow mesenchymal stem cell activity in vitro and bone regeneration in femoral bone defects in osteoporotic animal models. They hypothesized that local intra-marrow injection of teCaP particles could improve bone function because the teCaP can sustain release of biologically essential inorganic minerals and improve bone remodeling in osteoporosis. The teCaP and CaP particles were synthesized in simulated body fluid with and without adding silicon, zinc and strontium ions. Female rats (8 months) were ovariectomized (OVX) or sham-operated, and then intervened in the femoral marrow space at 12 months old. Groups include: (1) saline water; (2) CaP particles; and (3) teCaP particles. After 2-3 months of intervention, the sham groups showed higher bone mineral density (MBD) in the femur, and teCaP group increased the BMD in the OVX groups. The compressive strength of the OVX-teCaP group was significantly higher than that in the OVX-CaP group. Significant differences between OVX-teCaP and OVX-CaP groups were found for bone mineral microarchitecture, bone mineral density, and trace mineral content, but not for feces composition. These results confirm the teCaP particles could suppress osteoporotic bone loss by local intramarrow injection. Therefore, this biomaterial could be used as a next-generation combination treatment for osteoporotic trauma and osteoporosis itself.
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| 35. |
- Östberg, Anna-karin, 1979, et al.
(författare)
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Sublingual administration of 2-hydroxyethyl methacrylate enhances antibody responses to co-administered ovalbumin and Streptococcus mutans
- 2018
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Ingår i: Acta Odontologica Scandinavica. - : Informa UK Limited. - 0001-6357 .- 1502-3850. ; 76:5, s. 351-356
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The oral mucosa of patients undergoing dental procedures is often exposed to residual monomers leaking from incompletely cured acrylic resins. We investigated whether 2-hydroxyethyl methacrylate (HEMA) monomers applied to the sublingual mucosa in mice modulate the antibody responses towards co-administered ovalbumin (OVA) or live oral bacteria. Material and methods: OVA, live mouse oral commensal Lactobacillus murinus or live human oral commensal Streptococcus mutans were administered sublingually with or without HEMA to BALB/c mice on four weekly occasions. One week after the last administration, the experiment was terminated and serum antibody levels were analyzed using ELISA. Results: Significantly increased IgG and IgE anti-OVA antibody activity was found in the sera from mice immunized with OVA together with HEMA, as compared to mice immunized with OVA alone. Likewise, S. mutans together with HEMA induced an IgG anti-S, mutans antibody response that was significantly higher than the antibody response detected after application of S. mutans alone. No IgG anti-L murinus antibody response was detected in mice immunized with L. murinus together with HEMA, as compared to the background activity. Conclusions: We report that HEMA monomers have adjuvant properties when sublingually administered in combination with OVA or S. mutans.
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| 36. |
- Aarstad, Olav, et al.
(författare)
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Mechanical properties of composite hydrogels of alginate and cellulose nanofibrils
- 2017
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Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 9:8
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Tidskriftsartikel (refereegranskat)abstract
- Alginate and cellulose nanofibrils (CNF) are attractive materials for tissue engineering and regenerative medicine. CNF gels are generally weaker and more brittle than alginate gels, while alginate gels are elastic and have high rupture strength. Alginate properties depend on their guluronan and mannuronan content and their sequence pattern and molecular weight. Likewise, CNF exists in various qualities with properties depending on, e.g., morphology and charge density. In this study combinations of three types of alginate with different composition and two types of CNF with different charge and degree of fibrillation have been studied. Assessments of the composite gels revealed that attractive properties like high rupture strength, high compressibility, high gel rigidity at small deformations (Young’s modulus), and low syneresis was obtained compared to the pure gels. The effects varied with relative amounts of CNF and alginate, alginate type, and CNF quality. The largest effects were obtained by combining oxidized CNF with the alginates. Hence, by combining the two biopolymers in composite gels, it is possible to tune the rupture strength, Young’s modulus, syneresis, as well as stability in physiological saline solution, which are all important properties for the use as scaffolds in tissue engineering.
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| 37. |
- Ajaxon, Ingrid, 1983-
(författare)
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Can Bone Void Fillers Carry Load? : Behaviour of Calcium Phosphate Cements Under Different Loading Scenarios
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Calcium phosphate cements (CPCs) are used as bone void fillers and as complements to hardware in fracture fixation. The aim of this thesis was to investigate the possibilities and limitations of the CPCs’ mechanical properties, and find out if these ceramic bone cements can carry application-specific loads, alone or as part of a construct. Recently developed experimental brushite and apatite cements were found to have a significantly higher strength in compression, tension and flexion compared to the commercially available CPCs chronOS™ Inject and Norian® SRS®. By using a high-resolution measurement technique the elastic moduli of the CPCs were determined and found to be at least twice as high compared to earlier measurements, and closer to cortical bone than trabecular bone. Using the same method, Poisson's ratio for pure CPCs was determined for the first time. A non-destructive porosity measurement method for wet brushite cements was developed, and subsequently used to study the porosity increase during in vitro degradation. The compressive strength of the experimental brushite cement was still higher than that of trabecular bone after 25 weeks of degradation, showing that the cement can carry high loads over a time span sufficiently long for a fracture to heal. This thesis also presents the first ever fatigue results for acidic CPCs, and confirms the importance of testing the materials under cyclic loading as the cements may fail at stress levels much lower than the material’s quasi-static compressive strength. A decrease in fatigue life was found for brushite cements containing higher amounts of monetite. Increasing porosity and testing in a physiological buffer solution (PBS), rather than air, also decreased the fatigue life. However, the experimental brushite cement had a high probability of surviving loads found in the spine when tested in PBS, which has previously never been accomplished for acidic CPCs. In conclusion, available brushite cements may be able to carry the load alone in scenarios where the cortical shell is intact, the loading is mainly compressive, and the expected maximum stress is below 10 MPa. Under such circumstances this CPC may be the preferred choice over less biocompatible and non-degradable materials.
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| 38. |
- Ajaxon, Ingrid, et al.
(författare)
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Compressive fatigue properties of an acidic calcium phosphate cement—effect of phase composition
- 2017
-
Ingår i: Journal of materials science. Materials in medicine. - : Springer Science and Business Media LLC. - 0957-4530 .- 1573-4838. ; 28:3
-
Tidskriftsartikel (refereegranskat)abstract
- Calcium phosphate cements (CPCs) are synthetic bone grafting materials that can be used in fracture stabilization and to fill bone voids after, e.g., bone tumour excision. Currently there are several calcium phosphate-based formulations available, but their use is partly limited by a lack of knowledge of their mechanical properties, in particular their resistance to mechanical loading over longer periods of time. Furthermore, depending on, e.g., setting conditions, the end product of acidic CPCs may be mainly brushite or monetite, which have been found to behave differently under quasi-static loading. The objectives of this study were to evaluate the compressive fatigue properties of acidic CPCs, as well as the effect of phase composition on these properties. Hence, brushite cements stored for different lengths of time and with different amounts of monetite were investigated under quasi-static and dynamic compression. Both storage and brushite-to-monetite phase transformation was found to have a pronounced effect both on quasi-static compressive strength and fatigue performance of the cements, whereby a substantial phase transformation gave rise to a lower mechanical resistance. The brushite cements investigated in this study had the potential to survive 5 million cycles at a maximum compressive stress of 13 MPa. Given the limited amount of published data on fatigue properties of CPCs, this study provides an important insight into the compressive fatigue behaviour of such materials.
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| 39. |
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| 40. |
- Ajaxon, Ingrid, et al.
(författare)
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Elastic properties and strain-to-crack-initation of calcium phosphate bone cements : Revelations of a high-resolution measurement technique
- 2017
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Ingår i: Journal of The Mechanical Behavior of Biomedical Materials. - : Elsevier BV. - 1751-6161 .- 1878-0180. ; 74, s. 428-437
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Tidskriftsartikel (refereegranskat)abstract
- Calcium phosphate cements (CPCs) should ideally have mechanical properties similar to those of the bone tissue the material is used to replace or repair. Usually, the compressive strength of the CPCs is reported and, more rarely, the elastic modulus. Conversely, scarce or no data are available on Poisson's ratio and strain-to-crack-initiation. This is unfortunate, as data on the elastic response is key to, e.g., numerical model accuracy. In this study, the compressive behaviour of brushite, monetite and apatite cements was fully characterised. Measurement of the surface strains was done using a digital image correlation (DIC) technique, and compared to results obtained with the commonly used built-in displacement measurement of the materials testers. The collected data showed that the use of fixed compression platens, as opposed to spherically seated ones, may in some cases underestimate the compressive strength by up to 40%. Also, the built-in measurements may underestimate the elastic modulus by up to 62% as compared to DIC measurements. Using DIC, the brushite cement was found to be much stiffer (24.3 ± 2.3 GPa) than the apatite (13.5 ± 1.6 GPa) and monetite (7.1 ± 1.0 GPa) cements, and elastic moduli were inversely related to the porosity of the materials. Poisson's ratio was determined to be 0.26 ± 0.02 for brushite, 0.21 ± 0.02 for apatite and 0.20 ± 0.03 for monetite. All investigated CPCs showed low strain-to-crack-initiation (0.17–0.19%). In summary, the elastic modulus of CPCs is substantially higher than previously reported and it is concluded that an accurate procedure is a prerequisite in order to properly compare the mechanical properties of different CPC formulations. It is recommended to use spherically seated platens and measuring the strain at a relevant resolution and on the specimen surface.
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| 41. |
- Ajaxon, Ingrid, et al.
(författare)
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Evaluation of a porosity measurement method for wet calcium phosphate cements
- 2015
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Ingår i: Journal of biomaterials applications. - : Sage Publications. - 0885-3282 .- 1530-8022. ; 30:5, s. 526-536
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Tidskriftsartikel (refereegranskat)abstract
- The porosity of a calcium phosphate cement is a key parameter as it affects several important properties of the cement. However, a successful, non-destructive porosity measurement method that does not include drying has not yet been reported for calcium phosphate cements. The aim of this study was to evaluate isopropanol solvent exchange as such a method. Two different types of calcium phosphate cements were used, one basic (hydroxyapatite) and one acidic (brushite). The cements were allowed to set in an aqueous environment and then immersed in isopropanol and stored under three different conditions: at room temperature, at room temperature under vacuum (300 mbar) or at 37?C. The specimen mass was monitored regularly. Solvent exchange took much longer time to reach steady state in hydroxyapatite cements compared to brushite cements, 350 and 18 h, respectively. Furthermore, the immersion affected the quasi-static compressive strength of the hydroxyapatite cements. However, the strength and phase composition of the brushite cements were not affected by isopropanol immersion, suggesting that isopropanol solvent exchange can be used for brushite calcium phosphate cements. The main advantages with this method are that it is non-destructive, fast, easy and the porosity can be evaluated while the cements remain wet, allowing for further analysis on the same specimen.
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| 42. |
- Ajaxon, Ingrid, et al.
(författare)
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Long-term in vitro degradation of a high-strength brushite cement in water, PBS, and serum solution
- 2015
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Ingår i: BioMed Research International. - : Hindawi Publishing Corporation. - 2314-6133 .- 2314-6141.
-
Tidskriftsartikel (refereegranskat)abstract
- Bone loss and fractures may call for the use of bone substituting materials, such as calcium phosphate cements (CPCs). CPCs can be degradable, and, to determine their limitations in terms of applications, their mechanical as well as chemical properties need to be evaluated over longer periods of time, under physiological conditions. However, there is lack of data on how the in vitro degradation affects high-strength brushite CPCs over longer periods of time, that is, longer than it takes for a bone fracture to heal. This study aimed at evaluating the long-term in vitro degradation properties of a high-strength brushite CPC in three different solutions: water, phosphate buffered saline, and a serum solution. Microcomputed tomography was used to evaluate the degradation nondestructively, complemented with gravimetric analysis. The compressive strength, chemical composition, and microstructure were also evaluated. Major changes from 10 weeks onwards were seen, in terms of formation of a porous outer layer of octacalcium phosphate on the specimens with a concomitant change in phase composition, increased porosity, decrease in object volume, and mechanical properties. This study illustrates the importance of long-term evaluation of similar cement compositions to be able to predict the material’s physical changes over a relevant time frame.
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| 43. |
- Ajaxon, Ingrid, et al.
(författare)
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Mechanical Properties of Brushite Calcium Phosphate Cements
- 2017
-
Ingår i: The World Scientific Encyclopedia of Nanomedicine and Bioengineering II: Bioimplants, Regenerative Medicine, and Nano-Cancer Diagnosis and Phototherapy. - Singapore : World Scientific Pte Ltd.. - 9789814667586
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Bokkapitel (refereegranskat)
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| 44. |
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| 45. |
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| 46. |
- Alarcon, E I, et al.
(författare)
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Coloured cornea replacements with anti-infective properties : expanding the safe use of silver nanoparticles in regenerative medicine.
- 2016
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Ingår i: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 8:12, s. 6484-6489
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Tidskriftsartikel (refereegranskat)abstract
- Despite the broad anti-microbial and anti-inflammatory properties of silver nanoparticles (AgNPs), their use in bioengineered corneal replacements or bandage contact lenses has been hindered due to their intense yellow coloration. In this communication, we report the development of a new strategy to pre-stabilize and incorporate AgNPs with different colours into collagen matrices for fabrication of corneal implants and lenses, and assessed their in vitro and in vivo activity.
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| 47. |
- Albrektsson, Tomas, 1945
(författare)
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Are Oral Implants the Same As Teeth?
- 2019
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Ingår i: Journal of clinical medicine. - : MDPI AG. - 2077-0383. ; 8:9
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Tidskriftsartikel (refereegranskat)abstract
- Osseointegration of oral implants was initially discovered by Brånemark [...].
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| 48. |
- Albrektsson, Tomas, 1945
(författare)
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Hard tissue response
- 2016
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Ingår i: Murphy W., Black J., Hastings G. (eds) Handbook of Biomaterial Properties.. - New York, NY : Springer New York. - 9781493933037 ; , s. 581-592
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Bokkapitel (refereegranskat)abstract
- The initial tissue response when a biomaterial is implanted in the body is dependent on release of specific growth factors. It has been indicated by Frost [1] that the inevitable bone injury resulting from surgery and the presence of an implant will release various types of growth factors that will sensitize cells and promote cellular mitosis. This is a general healing response that will result in growth of all sorts of local connective tissues, bone as well as various types of soft tissue. © Springer Science+Business Media New York 2016.
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| 49. |
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| 50. |
- Albrektsson, Tomas, 1945, et al.
(författare)
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On inflammation-immunological balance theory—A critical apprehension of disease concepts around implants: Mucositis and marginal bone loss may represent normal conditions and not necessarily a state of disease
- 2019
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Ingår i: Clinical Implant Dentistry and Related Research. - : Wiley. - 1523-0899 .- 1708-8208. ; 21:1, s. 183-189
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Tidskriftsartikel (refereegranskat)abstract
- Background: Oral implants have displayed clinical survival results at the 95%-99% level for over 10 years of follow up. Nevertheless, some clinical researchers see implant disease as a most common phenomenon. Oral implants are regarded to display disease in the form of mucositis or peri-implantitis. One purpose of the present article is to investigate whether a state of disease is necessarily occurring when implants display soft tissue inflammation or partially lose their bony attachment. Another purpose of this article is to analyze the mode of defense for implants that are placed in a bacteria rich environment and to analyze when an obtained steady state between tissue and the foreign materials is disturbed. Materials and Methods: The present article is authored as a narrative review contribution. Results: Evidence is presented that further documents the fact that implants are but foreign bodies that elicit a foreign body response when placed in bone tissue. The foreign body response is characterized by a bony demarcation of implants in combination with a chronic inflammation in soft tissues. Oral implants survive in the bacteria-rich environments where they are placed due to a dual defense system in form of chronic inflammation coupled to immunological cellular actions. Clear evidence is presented that questions the automatic diagnostics of an oral implant disease based on the finding of so called mucositis that in many instances represents but a normal tissue response to foreign body implants instead of disease. Furthermore, neither is marginal bone loss around implants necessarily indicative of a disease; the challenge to the implant represented by bone resorption may be successfully counteracted by local defense mechanisms and a new tissue-implant steady state may evolve. Similar reactions including chronic inflammation occur in the interface of orthopedic implants that display similarly good long-term results as do oral implants, if mainly evaluated based on revision surgery in orthopedic cases. The most common mode of failure of orthopedic implants is aseptic loosening which has been found coupled to a reactivation of the inflammatory- immune system. Conclusions: Implants survive in the body due to balanced defense reactions in form of chronic inflammation and activation of the innate immune system. Ten year results of oral and hip /knee implants are hence in the 90+ percentage region. Clinical problems may occur with bone resorption that in most cases is successfully counterbalanced by the defense/healing systems. However, in certain instances implant failure will ensue characterized by bacterial attacks and/or by reactivation of the immune system that now will act to remove the foreign bodies from the tissues.
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