| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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| 7. |
- 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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| 8. |
- 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
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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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| 9. |
- 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
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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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| 10. |
- 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
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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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