| 1. |
- Danielsen, Nils, et al.
(författare)
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Inflammatory cells and mediators in the silicone chamber model for nerve regeneration
- 1993
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Ingår i: Biomaterials. - 0142-9612. ; 14:15, s. 5-1180
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Tidskriftsartikel (refereegranskat)abstract
- In the present study the inflammatory response was quantitatively evaluated during peripheral nerve regeneration. The fluid from silicone nerve regeneration chambers, inserted in rats, was collected during the early period of regeneration of transected sciatic nerves (6 h-7 d) and analysed with respect to inflammatory cells and mediators (leukotriene B4, LTB4, and interleukin-1 alpha, IL-1 alpha). Leucocytes were detected during the entire period (up to 7 d after implantation). The highest concentration was detected after 24 h. PMNG (polymorphonuclear granulocyte) was the predominant cell type in the chamber fluid during the initial 5d of regeneration. Analysis of the concentration of LTB4 demonstrated two peaks (at 24 h and 5 d). The IL-1 alpha concentration displayed an early and relatively smaller peak after 24 h and a second and much larger peak after 7 d, concomitant with an increase of the number of mononuclear cells.
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| 2. |
- Freij-Larsson, Christina, et al.
(författare)
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Adsorption behaviour of amphiphilic polymers at hydrophobic surfaces: Effects on protein adsorption
- 1996
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Ingår i: Biomaterials. - : Elsevier BV. - 1878-5905 .- 0142-9612. ; 17:22, s. 2199-2207
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption of four different amphiphilic polymers to a model surface has been studied, and the effects of the adsorbed amphiphiles on the subsequent adsorption of fibrinogen (Fg) and human serum albumin (HSA) at the surfaces were investigated. The amphiphilic polymers were one commercially available ABA block copolymer, Pluronic PE9400 (PE94), composed of poly(ethylene oxide) (A-blocks) and poly(propylene oxide) (B-block), and three graft copolymers, two with backbones of poly(styrene-co-acrylamide) (STY) and one with a backbone of poly(methyl methacrylate-co-ethylhexyl methacrylate) (ACRY). The backbones carried poly(ethylene oxide) (PEG) grafts, The model surface was a hydrophobic methylated silica surface (HMS). The amphiphilic polymers were adsorbed at the HMS surface from an ethanol/water solution. The adsorption process was monitored by ellipsometry. After rinsing with phosphate buffered saline (PBS), protein was added and the continued adsorption measured by ellipsometry. Surfaces modified by adsorption of the amphiphilic polymers were also characterized by contact angle measurements and X-ray photoelectron spectroscopy (XPS). According to these measurements the amphiphilic polymers adsorbed in significant amounts at the HMS surface. A limited study by atomic force microscopy (AFM), as well as the XPS measurements, suggests that both single molecules and micellar aggregates adsorb at the surface. ACRY and PE94 gave the highest levels of adsorption. As compared to the Pluronic block copolymer the graft copolymers were more strongly attached to the HMS surface, as shown by less desorption on rinsing with solvent. The ellipsometric results show that the adsorption of HSA and Fg at HMS surfaces containing preadsorbed amphiphilic polymer was significantly reduced as compared to the bare HMS surface. ACRY and PE94 showed the largest effects. Both polymers gave more than a 20-fold reduction of the Fg adsorption and a 10-fold reduction of the HSA adsorption. The STY polymers reduced the protein adsorption by a factor of 2-3.
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| 3. |
- Gabriel, B. L., et al.
(författare)
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Site-specific adhesion of Staphylococcus epidermidis (RP12) in Ti-Al-V metal systems
- 1994
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 15:8, s. 628-634
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Tidskriftsartikel (refereegranskat)abstract
- Staphylococcus epidermidis (RP12) adhesion patterns were studied on the following titanium (Ti)-aluminium (Al)-vanadium (V) metal systems: (i) microfabricated samples consisting of Ti, Al and V islands deposited onto Ti or V substrata, (ii) pure Ti, Al and V metals, and (iii) medical grade Ti6Al4-V alloy. All of these surfaces were covered with their respective oxides formed upon exposure of the metals to air. Quantitative analysis of the number of cells bound per unit area indicates that S. epidermidis (RP12) exhibits greatest adhesion to pure V surfaces. When exposed to surfaces having controlled spatial variations in chemical composition on the 10 mu m scale (microfabricated samples), the bacteria preferentially populate V islands versus Ti or Al substrata. In the case of the biphasic Ti6Al4V alloy, the bacteria tend to adhere to V-rich, mixed phase regions and phase boundaries. These findings demonstrate that enhanced and preferential adhesion of S. epidermidis (RP12) occurs on V surfaces in TI-Al-V metal systems and suggest that bacterial interactions are influenced by surface oxide composition.
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| 4. |
- Messner, Karola, et al.
(författare)
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Cartilage mechanics and morphology, synovitis and proteoglycan fragments in rabbit joint fluid after prosthetic meniscal substitution
- 1993
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Ingår i: Biomaterials. - 0142-9612. ; 14:3, s. 163-168
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Tidskriftsartikel (refereegranskat)abstract
- The effects of meniscal substitution with a Dacron® or Teflon® prosthesis on rabbit knee-joint cartilage were studied by indentation tests, gross and histological inspection, analysis of proteoglycan fragments in joint fluid and an evaluation of synovial changes. Cartilage mechanics and cartilage morphology were similarly abnormal after meniscectomy and meniscal substitution. The elevated concentrations of proteoglycan fragments in joint fluid and the more severe synovial changes in joints with a meniscal substitute, as compared to meniscectomy, probably resulted from irritation of the artificial implant, but also reflected the remaining effects from the necessary bone drilling. In this short-term experiment, the use of an artificial meniscal substitute could not prevent cartilage degeneration after meniscectomy.
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| 5. |
- Wesslén, Bengt, et al.
(författare)
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Protein adsorption of poly(ether urethane) surfaces modified by amphiphilic and hydrophilic polymers
- 1994
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Ingår i: Biomaterials. - : Elsevier BV. - 1878-5905 .- 0142-9612. ; 15:4, s. 278-284
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Tidskriftsartikel (refereegranskat)abstract
- A commercial biomedical poly(ether urethane), Pellethane 2363-80AE, was surface modified through the use of amphiphilic polymeric additives, and through surface grafting with poly(ethylene glycol), PEG. Two different amphiphilic polymers, Polymer C and Pluronic PE9400, were used as additives. Polymer C, a segmented polyurethane, was prepared from PEG1500, 4,4'-diphenylmethane diisocyanate and a C-16-C18 monoglyceride chain extender. Pluronic PE9400 is a propylene oxide-ethylene oxide tri-block co-polymer obtained from BASF. Adsorption of human albumin and fibrinogen to the modified surfaces was studied by means of radiolabelled proteins. By contact angle measurements and X-ray photoelectron spectra the amphiphilic polymers were shown to accumulate at the polyurethane surfaces. Adsorption of fibrinogen, in particular, was significantly reduced by the amphiphilic additives to levels similar to those obtained for Pellethane surfaces grafted with PEG 20000. In vitro clotting times for citrate-buffered blood in contact with the amphiphilic surfaces increased as compared with the unmodified ones.
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| 6. |
- Zhang, Y Z, et al.
(författare)
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Tissue response to commercial silicone and polyurethane elastomers after different sterilization procedures
- 1996
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Ingår i: Biomaterials. - : Elsevier BV. - 1878-5905 .- 0142-9612. ; 17:23, s. 2265-2272
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Tidskriftsartikel (refereegranskat)abstract
- Two different commercial polymeric materials, a silicone and a polyurethane (PUR), were studied with regard to correlations between the chemical and physical compositions of the polymer surfaces and the biological response on implantation. Test specimens of the materials were manufactured according to standard procedures. The specimens were implanted in rats for 10 and 90 days. Before implantation the polymers were sterilized in three different ways, namely, beta irradiation, ethylene oxide sterilization and steam sterilization. The polymers were characterized before and after the implantation with respect to the chemical composition and the morphology of the surfaces. After implantation the biological response was evaluated by counting numbers of macrophages, giant cells, fibroblasts and other cells present at the surfaces. The thickness of the fibrous capsule surrounding the test specimens was measured at the thickest and thinnest parts. PUR surfaces showed signs of degradation already after sterilization and after 10 to 90 days of implantation, pits and cracks appeared, especially in the ethylene oxide sterilized samples. However, differences in the biological responses were small and independent of the sterilization method. After 10 days of implantation the capsule thickness and the amounts of cell material adhering at the surfaces were different, and it appears that the silicone rubber induces more tissue response than PUR. The differences in the early tissue response evened out after 90 days implantation time and a steady state situation evolved, which was similar for the silicone and the polyurethane.
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| 7. |
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| 8. |
- Benesch, Johan, et al.
(författare)
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Blood protein adsorption onto chitosan
- 2002
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Ingår i: Biomaterials. - 0142-9612 .- 1878-5905. ; 23:12, s. 2561-2568
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Tidskriftsartikel (refereegranskat)abstract
- Chitosan was recently indicated to enhance osteogenesis, improve wound healing but to activate the coagulation and the complement systems. In the present study approximately 10nm thick chitosan film were prepared on aminopropyltriethoxysilane (APTES) coated silicon. The surfaces were incubated in serum or plasma and subsequently in antibodies towards key complement and contact activation of coagulation proteins. The deposited amounts were compared with those on hydrophilic and hydrophobic silicon, APTES and IgG coated reference samples. Although large amounts of serum deposited to chitosan only a weak transient activation of the complement system and no activation of the intrinsic pathway was observed. Upon acetylation the chitosan layer became a strong activator of the alternative pathway of the complement. After incubation in human plasma anti-fibrinogen deposited onto chitosan but not onto the acetylated chitosan, a finding that may explain previous observations of procoagulant activity by chitosan. Copyright © 2002 Elsevier Science Ltd.
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| 9. |
- Carlson, Johan, et al.
(författare)
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An ultrasonic pulse-echo technique for monitoring the setting of CaSO4-based bone cement
- 2003
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Ingår i: Biomaterials. - 0142-9612 .- 1878-5905. ; 24:1, s. 71-77
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Tidskriftsartikel (refereegranskat)abstract
- We present a new ultrasonic technique for monitoring the entire setting process of injectable bone cement. The problem with existing standards is their subjectivity. Because of this the results are not comparable between different research groups. A strong advantage with the proposed technique is that it is non-invasive and non-destructive, since no manipulation of the cement sample is needed once the measurement has started. Furthermore, the results are reproducible with small variations. The testing was performed on calcium sulfate cement using an ultrasonic pulse-echo approach. The results show that the acoustic properties of the cement are strongly correlated with the setting time, the density, and the adiabatic bulk modulus. The measured initial and final setting times agree well with the Gillmore needles standard. An important difference compared to the standards, is that the technique presented here allows the user to follow the entire setting process on-line.
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| 10. |
- Downs, Mark E.A., et al.
(författare)
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Optical and electrochemical detection of DNA
- 1988
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Ingår i: Biomaterials. - : Elsevier. - 0142-9612 .- 1878-5905. ; 9:1, s. 66-70
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Tidskriftsartikel (refereegranskat)abstract
- There is a growing demand for the production of a DNA biosensor with applications in medicine, the food industry, agriculture, veterinary science and environmental science. In this paper we describe methods for the optical and electrochemical detection of DNA using the enzyme horseradish peroxidase (EC 1.11.1.7) and glucose oxidase (EC 1.1.3.4). We have used bis-methylacridinium nitrate and luminol for the optical detection of DNA using a purpose built, inexpensive luminometer. Using this system detection limits of 10−11g of plasmid DNA have been observed. Electrochemical detection of DNA was carried out by the use of a fluoride ion selective electrode and stripping voltametry. DNA was detected down to 1 (10−9 − 10−10g of DNA by the enzymatic release of halogen ions from organohalogen compounds.
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| 11. |
- Edlund, Ulrica, et al.
(författare)
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Sterilization, storage stability and in vivo biocompatibility of poly(trimethylene carbonate)/poly(adipic anhydride) blends
- 2000
-
Ingår i: Biomaterials. - 0142-9612 .- 1878-5905. ; 21:9, s. 945-955
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Tidskriftsartikel (refereegranskat)abstract
- Biodegradable blends of poly(trimethylene carbonate) (PTMC) and poly(adipic anhydride) (PAA) have been proven to be strong candidates for controlled drug delivery polymers in vitro. We now report on the stability, sterilizability and in vivo local tissue response of these matrices. Blend matrices were sterilized by beta-radiation or ethylene oxide gas treatment, stored at different times and temperatures, and analyzed for changes in physicochemical properties. Moisture uptake at different relative humidities and storage times was determined. Sterilization procedures induced hydrolysis of the matrices. Ethylene oxide gas sterilization had a significantly more marked effect upon the matrix properties than radiation treatment. The onset of degradation was reflected in a decrease of crystallinity and molecular weight along with a change of blend composition. A similar onset of matrix degradation was observed upon storage in air. The physicochemical properties of the blends were well preserved upon storage under argon atmosphere. Biocompatibility of PTMC/PAA implants was assessed in the anterior chamber of rabbits eyes for 1 month. At selected post-operative time points, aqueous humor was analyzed for white blood cells and the corneal thickness was measured. The results suggest good biocompatability of PTMC-rich matrices, whereas fast eroding PAA-rich matrices caused inflammatory responses, due to a burst release of degradation products.
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| 12. |
- Eriksson, Cecilia, et al.
(författare)
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Interactions between human whole blood and modified TiO2-surfaces : Influence of surface topography and oxide thickness on leukocyte adhesion and activation
- 2001
-
Ingår i: Biomaterials. - : Elsevier. - 0142-9612 .- 1878-5905. ; 22:14, s. 1987-1996
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Tidskriftsartikel (refereegranskat)abstract
- An in vitro model (Nygren et al., J Lab Clin Med 129 (1997) 35-46) was used to investigate interactions between leukocytes and four modified TiO2-surfaces. Surface topography was measured using scanning electron microscopy and optical profilometry while Auger electron spectroscopy was used to determine surface composition and oxide thickness. The surfaces were either smooth or rough with either thin or thick oxides. All surfaces consisted of TiO2 covered by a carbonaceous layer. The surfaces were incubated with capillary blood for time periods of between 8 min and 32h. Immunofluorescence techniques together with computer aided image analysis and chemiluminescence technique were used to detect cell adhesion, expression of adhesion receptors and the zymosan-stimulated respiratory burst response. Leukocyte adhesion to the surfaces increased during the first hours of blood-material contact and then decreased. Polymorphonuclear granulocytes were the dominating leukocytes on all surfaces followed by monocytes. Cells adhering to rough surfaces had higher normalized expression of adhesive receptors than cells on smooth surfaces. Maximum respiratory burst response occurred earlier on the smooth than on the rough surfaces. In conclusion, topography had a greater impact than oxide thickness on most cellular reactions investigated, but the latter often had a dampening effect on the responses. (C) 2001 Elsevier Science Ltd. All rights reserved.
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| 13. |
- Goransson, A., et al.
(författare)
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Bone formation after 4 weeks around blood-plasma-modified titanium implants with varying surface topographies : An in vivo study
- 2003
-
Ingår i: Biomaterials. - 0142-9612 .- 1878-5905. ; 24:2, s. 197-205
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to investigate and compare the stability and bone ingrowth capacity to screw-shaped titanium implants with five different surface treatments. The implants were: (1) standard turned with a thin blood plasma coat (TP), (2) NaOH-etched dito with pore size 0.2-0.3µm (E), (3) NaOH-etched with pore size 0.2-0.3µm and a thin blood plasma coat (EP), (4) electrochemically oxidised with pore size 1-2µm (O), (5) electrochemically oxidised with pore size 1-2µm and a thin blood plasma coat (OP). A total of 66 implants were divided into the above-described five groups and inserted for 4 weeks into tibia and femur of 11 rabbits. The implants were evaluated by resonance frequency (RF) measurements at the time of insertion and removal, and analysed histomorphometrically at removal. The RF measurements showed that the implant stability was lower in soft bone compared to dense and increased with time. No significant differences were observed between the different surface modifications. The histomorphometric analysis revealed no statistically significant differences between the implants regarding bone-to-metal contact (BMC) and bone area inside the threads (BA). The above results indicate that thin blood plasma-coated and non-coated screw-shaped titanium implants with turned, NaOH-etched and electrochemically etched surface profiles integrate similarly to bone at 1 month of implantation. © 2002 Elsevier Science Ltd. All rights reserved.
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| 14. |
- Jansson, E., et al.
(författare)
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Ex vivo PMA-induced respiratory burst and TNF-a secretion elicited from inflammatory cells on machined and porous blood plasma clot-coated titanium
- 2002
-
Ingår i: Biomaterials. - 0142-9612 .- 1878-5905. ; 23:13, s. 2803-2815
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Tidskriftsartikel (refereegranskat)abstract
- The release of inflammatory mediators around implants and normal wounds may differ due to the presence of the solid surface. In this study, machined and sub-micron porous titanium implants with and without a 100nm thick blood plasma clot were inserted subcutaneously in rat for 3 or 24h. The cell recruitment to the interfaces, in vivo secretion of TNF-a and the ex vivo PMA-induced production of reactive oxygen species were subsequently investigated. The thin plasma clot coating gave rise to an increased ex vivo PMA-stimulated oxygen radical production by implant-associated cells at both implantation times, and an increased cell recruitment at 24h. The total TNF-a secretion was highest at sham sites and plasma clot-coated porous titanium at 24h. After 24h, the cell-type pattern in the exudate around the porous plasma-coated implant was more similar to that found at sham sites than that adjacent to the non-coated implants. No differences were observed between the machined Ti and the machined sub-micron porous Ti. © 2002 Elsevier Science Ltd. All rights reserved.
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| 15. |
- Jansson, Eva, et al.
(författare)
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In vitro preparation and ellipsometric characterization of thin blood plasma clot films on silicon
- 2001
-
Ingår i: Biomaterials. - 0142-9612 .- 1878-5905. ; 22:13, s. 1803-1808
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Tidskriftsartikel (refereegranskat)abstract
- The wound-healing process around implants differs from that of a normal healing without the inserted material. In this work, the composition of a natural wound surface was mimicked through clotting of a thin human blood plasma film with approximate ellipsometric thickness of 100nm onto differently pretreated silicon surfaces. Their stability was investigated by incubations in sodium dodecyl sulphate (SDS) solutions. The enzymatic clot degradation was induced through addition of human tissue plasminogen activator (t-PA) to the plasma and the surface protein remnants after the degradation were analyzed with polyclonal antibodies. The results show that the plasma films were not SDS resistant on hydrophilic silicon. However, stability was obtained after preparation on hydrophobic silicon or when albumin or fibrinogen was immobilized to silicon before the plasma incubations. Different surfaces bound different polyclonal antibodies after the clot film degradation. The methods indicate a simple means to improve or reestablish a normal tissue inflammatory response around biomaterials. Copyright © 2001 Elsevier Science Ltd.
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| 16. |
- Karlsson, Marjam, et al.
(författare)
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Initial in vitro interaction of osteoblasts with nano-porous alumina
- 2003
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Ingår i: Biomaterials. - 0142-9612 .- 1878-5905. ; 24:18, s. 3039-3046
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Tidskriftsartikel (refereegranskat)abstract
- In the present study we have used a characterised primary human cell culture model to investigate cellular interactions with nano-porous alumina. This material, prepared by anodisation, is being developed as a coating on titanium alloy implants. The structure of the alumina, as determined by X-ray diffraction and transmission electron microscopy, was amorphous. When studying cell/material interactions we used both biochemical and morphological parameters. Cell viability, proliferation and phenotype were assessed by measurement of redox reactions in the cells, cellular DNA, tritiated thymidine ([H-3]-TdR) incorporation and alkaline phosphatase (ALP) production. Results showed a normal osteoblastic growth pattern with increasing cell numbers during the first 2 weeks. A peak in cell proliferation was seen on day 3, after which cell growth decreased, followed by an increase in ALP production, thus indicating that the osteoblastic phenotype was retained on the alumina. Cell adhesion was observed, the osteoblast-like cells having a flattened morphology with filipodia attached to the pores of the material. SDS-PAGE and western blot measurements showed that the nano-porous alumina was able to adsorb fibronectin. Trace amounts of aluminium ions were measured in the surrounding medium, but no adverse effect on cell activity was observed.
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| 17. |
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| 18. |
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| 19. |
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| 20. |
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| 21. |
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| 22. |
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| 23. |
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| 24. |
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| 25. |
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| 26. |
- Lundgren, T, et al.
(författare)
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Separation of non-collagenous proteins of bone formed in titanium implants: experimental study in the rabbit tibia, using a bone harvest chamber.
- 1990
-
Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612. ; 11:3, s. 216-8
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Tidskriftsartikel (refereegranskat)abstract
- The non-collagenous proteins of mature cortical rabbit bone and 3 wk old bone specimens formed in titanium implant bone harvest chambers, were separated by means of fine pressure liquid chromatography. It was found that a sufficient amount of bone could be obtained from five bone harvest chambers in five rabbits during a period of 15 wk. A different protein chromatographic pattern was found in bone grown in bone harvest chambers as compared to normal cortical bone from the same region. This indicates a difference in bone quality and shows that this implant design can be used for biochemical analysis of bone formed adjacent to a biomaterial.
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| 27. |
- Nimeri, G, et al.
(författare)
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The influence of plasma proteins and platelets on oxygen radical production and F-actin distribution in neutrophils adhering to polymer surfaces
- 2002
-
Ingår i: Biomaterials. - 0142-9612 .- 1878-5905. ; 23:8, s. 1785-1795
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that blood cell interactions with artificial surfaces might have deleterious effects on host tissue, however, the mechanisms involved are far from understood. In this study, neutrophil-platelet interaction on uncoated or protein-coated polymer surfaces was investigated. Cell spreading, reorganization of actin filaments and release of oxygen metabolites (measured as luminol-amplified chemiluminescence) were used as criteria for cell activation on positively charged, hydrophilic 1,2-diaminocyclohexane, and negatively charged, hydrophobic hexamethylene-disiloxane. The model surfaces were made by radio frequency plasma discharge polymerization. Neutrophil contact with the uncoated polymers induced a prolonged generation of oxygen radicals. Precoating of the polymer surfaces with human serum albumin (HSA) or fibrinogen, markedly reduced neutrophil activation, whereas coating with human immunoglobulin G (IgG), a well-known opsonin, resulted in significantly higher levels of cell activation. Consequently, protein coating overruled the activating effects of the polymer surfaces. The presence of unstimulated or thrombin-stimulated platelets markedly increased the reactivity of neutrophils against fibrinogen- and IgG-coated surfaces. However, neutrophils remained relatively unreactive in the presence of platelets on HSA-treated surfaces. Comparison of the different types of surfaces used, reveals a correlation between the degree of cell spreading, reorganization of the actin cytoskeleton and the amount of oxygen radicals produced. Our results suggest that the acute inflammatory reaction on a biomaterial surface is highly dependent on the nature and composition of the first adsorbed protein layer and the extent of platelet activation.
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| 28. |
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| 29. |
- Persson-Sjögren, Solveig, et al.
(författare)
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Effects of glass ionomers and dental resin composites on viability of beta-cells and insulin release in isolated islets of Langerhans.
- 2003
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Ingår i: Biomaterials. - 0142-9612 .- 1878-5905. ; 24:21, s. 3741-3746
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Tidskriftsartikel (refereegranskat)abstract
- Information on the biocompatibility of glass ionomers and resin composites is sparse. To extend the scale of biological testing we evaluated the influence of those materials on insulin secretion at whole organ level in vitro. The effects on insulin secretion of three glass ionomers and two resin composites, aged for 1 week, were studied in isolated mouse islets of Langerhans at basal (5.5mM) and at stimulatory (11.1mM) D-glucose concentrations. In addition, viability of single mouse beta-cells was evaluated. The effect of glass ionomer specimens aged for 1 and 4 months on insulin secretion at 11.1mM D-glucose was also studied. None of the materials affected the viability of the beta-cells. At 5.5mM D-glucose none of the materials affected the insulin secretion. At 11.1mM D-glucose, the glass ionomers only decreased the secretion and glass ionomers aged for 1 month still decreased insulin release whereas after 4 months ageing only one of the glass ionomers affected the release. The result shows a dynamic effect on insulin release of the elements and/or compounds released from the specimens.
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| 30. |
- Sennerby, Lars, 1960, et al.
(författare)
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Acute tissue reactions to potassium alginate with and without colour/flavour additives.
- 1987
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612. ; 8:1, s. 49-52
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Tidskriftsartikel (refereegranskat)abstract
- The acute tissue reactions to potassium alginate, locally applied to a microvascular bed, were studied with the use of the vital microscopic hamster cheek pouch model combined with correlative histology. This experimental model permitted us to study microvascular permeability, blood flow, vessel diameters and leucocyte adhesion to vessel walls intravitally, and leucocyte migration and mastcell degranulation histologically. Deionized water alone and potassium alginate with flavour and colour mixed in saline was found to cause severe microvascular alterations, while potassium alginate, without flavour and colour, but mixed in saline and applied to the microvasculature resulted in a minor inflammatory reaction.
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| 31. |
- Sennerby, Lars, 1960, et al.
(författare)
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Influence of indomethacin on the regeneration of cortical bone within titanium implants in rabbits.
- 1993
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612. ; 14:2, s. 156-8
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Tidskriftsartikel (refereegranskat)abstract
- The influence of indomethacin on cortical bone regeneration was studied in bone harvest chambers made of commercially pure titanium and inserted in rabbit tibia. Newly formed bone was harvested in situ every 3 wk for 33 wk. Indomethacin (1 mg/kg body weight) was given daily as subcutaneous injections for two periods, followed by two control periods with no drug administration and the same schedule was followed for indomethacin at a dose of 4 mg/kg body weight. These indomethacin dosages did not statistically influence the cortical bone regeneration.
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| 32. |
- Sennerby, Lars, 1960, et al.
(författare)
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Tissue response to titanium implants in experimental antigen-induced arthritis.
- 1993
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612. ; 14:6, s. 413-22
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Tidskriftsartikel (refereegranskat)abstract
- The healing of threaded, non-alloyed titanium implants in bone was studied in an experimental model of monoarticular arthritis in New Zealand white rabbits. Immunization with bovine serum albumin (BSA) and repeated intra-articular injections with BSA elicited an immune response and clinical signs of inflammation. Implants were inserted and 6 wk after surgery, with full weight-bearing, the rabbits were killed by perfusion fixation. Light microscopic morphometry showed that the cartilage was thinner and the subchondral bone had a lower density in the arthritic joints compared to the control side. The titanium implants in the arthritic joints had a lesser degree of mineralized bone-implant contact and surrounding bone than the implants inserted in control joints. The present study shows that the healing of titanium implants in the rabbit knee joint is impaired in experimental immunologic arthritis. This model may be useful for the study of biomaterial-tissue interactions under pathological conditions.
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| 33. |
- Suska, F., et al.
(författare)
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IL-1a, IL-1ß and TNF-a secretion during in vivo/ex vivo cellular interactions with titanium and copper
- 2003
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Ingår i: Biomaterials. - 0142-9612 .- 1878-5905. ; 24:3, s. 461-468
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Tidskriftsartikel (refereegranskat)abstract
- Titanium (Ti) and copper (Cu) were used to evaluate cytokine secretion around materials with different chemical properties. Ti disks were coated with Cu or left uncoated. The disks were inserted subcutaneously in rats for 1, 3, 12, 18, 24 and 48h. Interleukin-1a (IL-1a), IL-1ß and tumor necrosis factor-a (TNF-a) concentrations were measured in vivo around the materials, in sham operated sites, and after ex vivo incubation of surface adherent cells. Ti and Cu revealed distinct cytokine expression patterns. Cu recruited cells showed higher and prolonged release of IL-1a than Ti at longer times (>24h), whereas Ti exhibited a transient IL-1a response at earlier periods (<24h). An early enhanced secretion of TNF-a characterized Ti. Low amounts of IL-1ß were found around both materials. Sham site recruited cells produced lower levels of cytokines. The results after ex vivo incubations were similar to those in vivo. This study shows that material chemical properties influence early cytokine production. The Ti-associated transient rise of IL-1a and TNF-a may be of importance for the early tissue response around biocompatible materials, while a delayed high IL-1a expression could be a marker of inflammation induced by toxic materials. © 2002 Elsevier Science Ltd. All rights reserved.
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| 34. |
- Tosatti, S., et al.
(författare)
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Peptide functionalized poly(L-lysine)-g-poly(ethylene glycol) on titanium : Resistance to protein adsorption in full heparinized human blood plasma
- 2003
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Ingår i: Biomaterials. - 0142-9612 .- 1878-5905. ; 24:27, s. 4949-4958
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Tidskriftsartikel (refereegranskat)abstract
- The graft copolymer poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) and its RGD- and RDG-functionalized derivatives (PLL-g-PEG/PEG-peptide) were assembled from aqueous solutions on titanium (oxide) surfaces. The polymers were characterized by NMR in order to determine quantitatively the grafting ratio, g (Lys monomer units/PEG side chains), and the fraction of the PEG side chains carrying the terminal peptide group. The titanium surfaces modified with the polymeric monomolecular adlayers were exposed to full heparinized blood plasma. The adsorbed masses were measured by in situ ellipsometry. The different PLL-g-PEG-coated surfaces showed, within the detection limit of the ellipsometric technique, no statistically significant protein adsorption during exposure to plasma for 30min at 22°C or 37°C, whereas clean, uncoated titanium surfaces adsorbed approximately 350ng/cm2 of plasma proteins. The high degree of resistance of the PEGylated surface to non-specific adsorption makes peptide-modified PLL-g-PEG a useful candidate for the surface modification of biomedical devices such as implants that are capable of eliciting specific interactions with integrin-type cell receptors even in the presence of full blood plasma. The results refer to short-term blood plasma exposure that cannot be extrapolated a priori to long-term clinical performance. © 2003 Elsevier Ltd. All rights reserved.
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| 35. |
- Wetterö, Jonas, 1972-, et al.
(författare)
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On the binding of complement to solid artificial surfaces in vitro
- 2002
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Ingår i: Biomaterials. - 0142-9612 .- 1878-5905. ; 23:4, s. 981-991
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Tidskriftsartikel (refereegranskat)abstract
- Since the realization of a complement activation capacity by artificial surfaces upon contact with blood, a common belief has evolved that charged nucleophilic surface groups such as amine (–NH2) and hydroxyl (–OH) react with and eventually bind to the internal thioester in complement factor 3 (C3). A covalent amide or ester linkage is thereby supposed to form between C3b and the surface itself. In this report, we present complement surface binding data by null-ellipsometry for two nucleophilic surfaces (–NH2 and –OH), for surfaces with immunoglobulin G (IgG) covalently bound, and for IgG spontaneously pre-adsorbed to hydrophobic silicon. The results reveal that the plasma proteins that were deposited during complement activation became eluted by sodium dodecyl sulfate. Hence the direct covalent binding between C3 and solid nucleophilic surfaces seems to be only of moderate importance, at least during shorter serum incubations. This strongly suggests that the prevalent covalent linkage model between solid artificial surfaces and C3b is not accurate. Instead we suggest a more pronounced role for C3 associations to other adsorbed proteins and/or electrostatic and hydrophobic protein–surface interactions.
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| 36. |
- Wetterö, Jonas, 1972-, et al.
(författare)
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Platelets stimulated by IgG-coated surfaces bind and activate neutrophils through a selectin-dependent pathway
- 2003
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Ingår i: Biomaterials. - 0142-9612 .- 1878-5905. ; 24:9, s. 1559-1573
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Tidskriftsartikel (refereegranskat)abstract
- Blood platelets bind rapidly to foreign surfaces and interact with adsorbed proteins and neutrophil granulocytes. We demonstrate by use of luminol-amplified chemiluminescence under stirred and non-stirred conditions that platelets at IgG-coated surfaces amplify the neutrophil extracellular release of reactive oxygen species (ROS). The neutrophil response involved tyrosine phosphorylation, but was only in part induced by neutrophil Fcγ-receptor stimulation. The platelet mediated effects were contact-dependent since the respiratory burst was inhibited when the IgG-stimulated platelets were removed by filtration, but not when they were fixed in paraformaldehyde. Bodipyphallacidin-staining of filamentous actin (F-actin) revealed that an actin-dependent platelet adhesion supported the subsequent adhesion and spreading of neutrophils. The neutrophil ROS-response was lowered when the interaction between platelet P-selectin (CD62P) and neutrophil P-selectin glycoprotein ligand-l (PSGL-1 or CD162) was inhibited. The blocking of L-selectin (CD62L) or blocking of the interaction between platelet glycoprotein (Gp) IIb/IIIa and neutrophil complement receptor 3 (CR3) showed no effect. We conclude that platelet activation on immobilized IgG trigger a contact-dependent “frustrated” phagocytosis by neutrophils, associated with a release of toxic ROS.
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| 37. |
- Ajalloueian, Fatemeh, et al.
(författare)
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Constructs of electrospun PLGA, compressed collagen and minced urothelium for minimally manipulated autologous bladder tissue expansion
- 2014
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 35:22, s. 5741-5748
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Tidskriftsartikel (refereegranskat)abstract
- Bladder regeneration based on minced bladder mucosa in vivo expansion is an alternative to in vitro culturing of urothelial cells. Here, we present the design of a hybrid, electrospun poly(lactic-co-glycolide) (PLGA) - plastically compressed (PC) collagen scaffold that could allow in vivo bladder mucosa expansion. Optimisation of electrospinning was performed in order to obtain increased pore sizes and porosity to consolidate the construct and to support neovascularisation and tissue ingrowth. Tensile tests showed an increase in average tensile strength from 0.6 MPa for PC collagen to 3.57 MPa for the hybrid construct. The optimised PLGA support scaffold was placed between two collagen gels, and the minced tissue was distributed either on top or both on top and inside the construct prior to PC; this was then cultured for up to four weeks. Morphology, histology and SEM demonstrated that the construct maintained its integrity throughout cell culture. Cells from minced tissue migrated, expanded and re-organised to a confluent cell layer on the top of the construct after two weeks and formed a multilayered urothelium after four weeks. Cell morphology and phenotype was typical for urothelial mucosa during tissue culture. (C) 2014 Elsevier Ltd. All rights reserved.
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| 38. |
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| 39. |
- Alarcon, Emilio I, et al.
(författare)
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The biocompatibility and antibacterial properties of collagen-stabilized, photochemically prepared silver nanoparticles
- 2012
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Ingår i: Biomaterials. - : Elsevier. - 0142-9612 .- 1878-5905. ; 33:19, s. 4947-4956
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Tidskriftsartikel (refereegranskat)abstract
- Spherical 3.5 nm diameter silver nanoparticles (AgNP) stabilized in type I collagen (AgNP@collagen) were prepared in minutes (5-15 min) at room temperature by a photochemical method initiated by UVA irradiation of a water-soluble non-toxic benzoin. This biocomposite was examined to evaluate its biocompatibility and its anti-bacterial properties and showed remarkable properties. Thus, while keratinocytes and fibroblasts were not affected by AgNP@collagen, it was bactericidal against Bacillus megaterium and E. coli but only bacteriostatic against S. epidermidis. In particular, the bactericidal properties displayed by AgNP@collagen were proven to be due to AgNP in AgNP@collagen, rather than to released silver ions, since equimolar concentrations of Ag are about four times less active than AgNP@collagen based on total Ag content. This new biocomposite was stable over a remarkable range of NaCl, phosphate, and 2-(N-morpholino)ethanesulfonic acid concentrations and for over one month at 4 degrees C. Circular dichroism studies show that the conformation of collagen in AgNP@collagen remains intact. Finally, we have compared the properties of AgNP@collagen with a similar biocomposite prepared using alpha-poly-L-Lysine and also with citrate stabilized AgNP; neither of these materials showed comparable biocompatibility, stability, or anti-bacterial activity.
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| 40. |
- Almlöf, Martin, et al.
(författare)
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Molecular dynamics study of heparin based coatings
- 2008
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 29:33, s. 4463-4469
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Tidskriftsartikel (refereegranskat)abstract
- Heparin based surface coatings can be used to improve the biocompatibility of metallic surfaces such as vascular stents. Here, we report molecular dynamics simulations of a macromolecular conjugate of heparin used to prepare such surfaces. The structural properties of the heparin conjugate are investigated for different degrees of hydration, to allow comparison with spectroscopic results. The simulations show that the polymer becomes more compact with an increasing degree of inter-chain interactions as the hydration increases. This is also accompanied by changes in the interaction patterns among the heparin chains, where counter ions become looser associated with the disaccharide units and their strong interactions can be partly replaced by water molecules and heparin hydroxyl groups. The structural information that can be obtained from computer simulations of this type of coatings can be very valuable for understanding and further development of functional interfaces, since very little is known experimentally regarding their detailed structural properties. (C) 2008 Elsevier Ltd. All rights reserved.
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| 41. |
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| 42. |
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| 43. |
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| 44. |
- Apelgren, Peter, et al.
(författare)
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Vascularization of tissue engineered cartilage-Sequential in vivo MRI display functional blood circulation
- 2021
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 276
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Tidskriftsartikel (refereegranskat)abstract
- Establishing functional circulation in bioengineered tissue after implantation is vital for the delivery of oxygen and nutrients to the cells. Native cartilage is avascular and thrives on diffusion, which in turn depends on proximity to circulation. Here, we investigate whether a gridded three-dimensional (3D) bioprinted construct would allow ingrowth of blood vessels and thus prove a functional concept for vascularization of bioengineered tissue. Twenty 10 x 10 x 3-mm 3Dbioprinted nanocellulose constructs containing human nasal chondrocytes or cell-free controls were subcutaneously implanted in 20 nude mice. Over the next 3 months, the mice were sequentially imaged with a 7 T small-animal MRI system, and the diffusion and perfusion parameters were analyzed. The chondrocytes survived and proliferated, and the shape of the constructs was well preserved. The diffusion coefficient was high and well preserved over time. The perfusion and diffusion patterns shown by MRI suggested that blood vessels develop over time in the 3D bioprinted constructs; the vessels were confirmed by histology and immunohistochemistry. We conclude that 3D bioprinted tissue with a gridded structure allows ingrowth of blood vessels and has the potential to be vascularized from the host. This is an essential step to take bioengineered tissue from the bench to clinical practice.
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| 45. |
- Arvidsson, Sara, 1977-, et al.
(författare)
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Blood plasma contact activation on silicon, titanium and aluminium.
- 2007
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 28:7, s. 1346-54
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, blood plasma protein deposition to spontaneously air oxidized silicon, titanium and aluminium was re-investigated in vitro. Immunological- and null ellipsometry methods were used to detect and quantitate adsorbed proteins, RIA methods to study the retention of preadsorbed 125I-HSA upon exposure to buffer or blood plasma, and kallikrein-specific colorimetric substrate S-2302 to follow the surface generation of kallikrein. The results show that the contact activation of coagulation and complement systems are connected on Si and Ti, but not on Al, via coagulation factor XII. Preadsorbed 125I-HSA was most readily displaced on silicon, followed by titanium and aluminium. The surfaces displayed different antibody binding patterns after short and long-time exposures to plasma. Titanium and silicon bound anti-HMWK after 1 min in plasma, but aluminium did not. When the plasma incubation time was prolonged up to 2h the anti-HMWK binding disappeared totally on titanium and decreased on silicon. During the same time period, anti-C3c binding increased to the three types of surfaces. Also, the anti-C3c binding onto Si and Ti, but not Al, disappeared after incubation in Factor XII deficient plasma or when a specific coagulation factor XII (Factor XII) inhibitor, corn trypsin inhibitor (CTI) was added to normal plasma. The surface contacted plasmas cleaved the kallikrein-specific reagent S-2302 both after single surface contact, and after reincubation of surfaces in fresh plasma. The results show that C3b and Factor XIIa and their degradation products were retained at the surfaces.
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| 46. |
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| 47. |
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| 48. |
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| 49. |
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| 50. |
- Bayat, Narges, et al.
(författare)
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Vascular toxicity of ultra-small TiO2 nanoparticles and single walled carbon nanotubes in vitro and in vivo
- 2015
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 63, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- Ultra-small nanoparticles (USNPs) at 1-3 nm are a subset of nanoparticles (NPs) that exhibit intermediate physicochemical properties between molecular dispersions and larger NPs. Despite interest in their utilization in applications such as theranostics, limited data about their toxicity exist. Here the effect of TiO2-USNPs on endothelial cells in vitro, and zebrafish embryos in vivo, was studied and compared to larger TiO2-NPs (30 nm) and to single walled carbon nanotubes (SWCNTs). In vitro exposure showed that TiO2-USNPs were neither cytotoxic, nor had oxidative ability, nevertheless were genotoxic. In vivo experiment in early developing zebrafish embryos in water at high concentrations of TiO2-USNPs caused mortality possibly by acidifying the water and caused malformations in the form of pericardial edema when injected. Myo1C involved in glomerular development of zebrafish embryos was upregulated in embryos exposed to TiO2-USNPs. They also exhibited anti-angiogenic effects both in vitro and in vivo plus decreased nitric oxide concentration. The larger TiO2-NPs were genotoxic but not cytotoxic. SWCNTs were cytotoxic in vitro and had the highest oxidative ability. Neither of these NPs had significant effects in vivo. To our knowledge this is the first study evaluating the effects of TiO2-USNPs on vascular toxicity in vitro and in vivo and this strategy could unravel USNPs potential applications.
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