| 1. |
- Asplund, Basse, et al.
(author)
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Effects of hydrolysis on a new biodegradable co-polymer
- 2006
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In: Journal of Biomaterials Science. Polymer Edition. - : Informa UK Limited. - 0920-5063 .- 1568-5624. ; 17:6, s. 615-630
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Journal article (peer-reviewed)abstract
- The aim of this study was to examine the feasibility of using a new low-modulus biodegradable thermoplastic elastomer for in vivo application as a stent cover. The new polymer, a thermoplastic elastomer, consists of a three-armed co-polymer of poly(lactide)acid (PLLA), poly(trimethylene carbonate) (PTMC) and poly(caprolactone) (PCL). A degradation study was performed in a buffer solution at 37 degrees C for 4 and 6 weeks. The effect of degradation on mechanical properties was studied by stress-strain measurements and explained by using modulated DSC, GPC and mass measurements. A tapered block of PLLA and trimethylene carbonate connecting the crystalline outer part and the inner elastic part was highly susceptible to hydrolysis and caused rapid degradation and subsequent loss of mechanical properties. Random chain scission and homogenous hydrolysis resulted in a loss in mass and molecular weight. After 6 weeks of in vitro hydrolysis the molecular weight had decreased 54% and the elongation-at-break dropped from more than 300% to 90%. A medium free cell seeding study showed that endothelial cells adhered well to the polymeric material. An indicative animal study with the polymer acting as a stent cover showed very low levels of inflammation however, pronounced neointima thickening was observed which was probably due to the premature failure of the material.
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| 2. |
- Aucoin, L, et al.
(author)
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Interactions of corneal epithelial cells and surfaces modified with cell adhesion peptide combinations
- 2002
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In: Journal of Biomaterials Science. Polymer Edition. - : Vsp. - 0920-5063 .- 1568-5624. ; 13:4, s. 447-462
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Journal article (peer-reviewed)abstract
- In order to facilitate the adhesion of corneal epithelial cells to a poly dimethyl siloxane (PDMS) substrate ultimately for the development of a synthetic keratoprosthesis, PDMS surfaces were modified by covalent attachment of combinations of cell adhesion and synergistic peptides derived from laminin and fibronectin. Peptides studied included YIGSR and its synergistic peptide PDSGR from laminin and the fibronectin derived RGDS and PHSRN. Surfaces were modified with combinations of peptides determined by an experimental design. Peptide surface densities, measured using 125-I labeled tyrosine containing analogs, were on the order of pmol/cm(2). Surface density varied as a linear function of peptide concentration in the reaction solution, and was different for the different peptides examined. The lowest surface density at all solution fractions was obtained with GYRGDS, while the highest density was consistently obtained with GYPDSGR. These results provide evidence that the surfaces were modified with multiple peptides. Water contact angles and XPS results provided additional evidence for differences in the chemical composition of the various surfaces. Significant differences in the adhesion of human corneal epithelial cells to the modified surfaces were noted. Statistical analysis of the experimental adhesion results suggested that solution concentration YIGSR, RGDS, and PHSRN as well as the interaction effect of YIGSR and PDSGR had a significant effect on cell interactions. Modification with multiple peptides resulted in greater adhesion than modification with single peptides only. Surface modification with a control peptide PPSRN in place of PHSRN resulted in a decrease in cell adhesion in virtually all cases. These results suggest that surface modification with appropriate combinations of cell adhesion peptides and synergistic peptides may result in improved cell surface interactions.
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| 3. |
- Azuma, Tomoyuki, et al.
(author)
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Poly(2-aminoethyl methacrylate)-based polyampholyte brush surface with carboxylic groups to improve blood compatibility
- 2020
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In: Journal of Biomaterials Science. Polymer Edition. - : Taylor & Francis Group. - 0920-5063 .- 1568-5624. ; 31:5, s. 679-693
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Journal article (peer-reviewed)abstract
- Zwitterionic material-based polymer brush significantly prevents protein adsorption and cell adhesion, which leads to the blood compatibility. However, zwitterionic polymer itself is difficult to be modified further, for the blood compatibility since the charged balance is impaired after the modification. In this research, chemically modifiable mixed charge polymer brush is designed, without impairing its characteristics. Condensed mixed charge polymer brush will work like zwitterionic material because neighbouring opposite charge is reported to be important in the zwitterionic material. Cationic polymer brush with primary amine group, which is based on 2-aminoethyl methacrylate (AEMA), was prepared and modified by succinic anhydride to obtain carboxylic group induced poly(AEMA). The ratio of primary amine group and carboxylic group was optimized to obtain the polyampholyte brush. The blood compatibility was evaluated by measuring coagulation/complement activation, protein adsorption and cell adhesion induced by the polymer. Our designed cationic-based polyampholyte brush prevented coagulation/complement activation comparable to poly(2-methacryloyloxyethyl phosphorylcholine) brush, based on intra-monomer interaction, because condensed mix charge works like zwitterion.
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| 4. |
- Benesch, Johan, et al.
(author)
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Protein adsorption to oligo(ethylene glycol) self-assembled monolayers : Experiments with fibrinogen, heparinized plasma, and serum
- 2001
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In: Journal of Biomaterials Science. Polymer Edition. - : Taylor & Francis. - 0920-5063 .- 1568-5624. ; 12:6, s. 581-597
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Journal article (peer-reviewed)abstract
- Low protein adsorption is believed advantageous for blood-contacting materials and ethylene glycols (EG)-based polymeric compounds are often attached to surfaces for this purpose. In the present study, the adsorption of fibrinogen, serum, and plasma were studied by ellipsometry on a series of well-defined oligo(EG) terminated alkane-thiols self-assembled on gold. The layers were prepared with compounds of the general structure HS-(CH2)15-CONH-EGn, where n = 2, 4, and 6. Methoxy-terminated tri(EG) undecanethiol and hydroxyl-terminated hexadecanethiol self-assembled monolayers (SAMs) were used as references. The results clearly demonstrate that the adsorption depends on the experimental conditions with small amounts of fibrinogen adsorbing from a single protein solution, but larger amounts of proteins from serum and plasma. The adsorption of fibrinogen and blood plasma decreased with an increasing number of EG repeats and was temperature-dependent. Significantly less serum adsorbed to methoxy tri(EG) than to hexa(EG) and more proteins remained on the latter surface after incubation in a sodium dodecyl sulfate (SDS) solution, indicating a looser protein binding to the methoxy-terminated surface. All surfaces adsorbed complement factor 3(C3) from serum and plasma, although no surface-mediated complement activation was observed. The present study points to the importance of a careful choice of the protein model system before general statements regarding the protein repellant properties of potential surfaces can be made.
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| 5. |
- Boelgen, Nimet, et al.
(author)
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Cryogelation for preparation of novel biodegradable tissue-engineering scaffolds
- 2007
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In: Journal of Biomaterials Science. Polymer Edition. - : Informa UK Limited. - 0920-5063 .- 1568-5624. ; 18:9, s. 1165-1179
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Journal article (peer-reviewed)abstract
- 2-Hydroxyethyl methacrylate-L-lactate (HEMA-LLA) and HEMA-L-lactate-dextran (HEMA-LLA-D) were synthesized. H-1-NMR confirmed the formation of these oligomers and macromers. Cryogels with different pore structures were prepared using different amounts of HEMA, HEMA-LLA and HEMA-LLA-D by a cryogelation technique. SEM micrographs exhibited pore morphologies. Cryogels were highly porous with interconnected pore structures, opaque, spongy and highly elastic. It was possible to compress them to remove the water in the pores and to return to their original form just by immersing them in water in few minutes, which was quite reproducible. Their swelling abilities, compressive strengths and degradation in buffer solutions were found to be related with their structural properties which was controlled by changing the cryogelation recipe.
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| 6. |
- Duan, X, et al.
(author)
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Novel dendrimer based polynrethanes for PEO incorporation
- 2002
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In: Journal of Biomaterials Science. Polymer Edition. - : Vsp. - 0920-5063 .- 1568-5624. ; 13:6, s. 667-689
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Journal article (peer-reviewed)abstract
- A series of segmented polyurethanes based on methylene diisocyanate/ poly (tetramethylene oxide) and chain extended with either ethylene diamine or butane diol in combination with a generation 2 polypropylenimine octaamine dendrimer were synthesized. For polymer synthesis, the dendrimers were protected with either t-boc or Fmoc groups and were incorporated into the polyurethane microstructure to permit further functionalization with biologically active groups. Following deprotection, the dendrimers were reacted with succinimidyl propionate polyethylene oxide (SPA-PEO) to improve the protein resistance of the polymers and to examine the potential of this technique for polymer functionalization. Different synthesis techniques were examined to optimize the incorporation of the PEO into the polymer microstructure. Incorporation of the dendrimers and the PEO were confirmed by NMR and FTIR. Gel permeation chromatography was used to examine the molecular weights of the various polyurethanes. The dendrimer incorporated polymers had significantly lower molecular weights than the ED or BDO chain extended controls, likely due to lower reactivity of the dendrimers as a result of steric factors. Following PEO reaction, the molecular weights of the resultant polymers were consistent with the levels of PEO incorporation noted by comparison of peak intensities in the NMR spectra. Due to the highly hydrophilic nature of the PEO, some migration to the polymer surface was expected. Water contact angles and XPS, used to characterize the surfaces, suggest that there was some PEO enrichment at the surface of the polymers. Adsorption of radiolabeled fibrinogen to the polymer surfaces was decreased by a factor of approximately 40% in some of the PEO incorporated polymers. There were also differences in the patterns of plasma protein adsorption on the various surfaces as evaluated by SDS PAGE and immunoblotting. Therefore, the use of dendrimers in biomaterials for incorporation of a large number of functional groups seems to be promising.
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| 7. |
- Giavaresi, Gianluca, et al.
(author)
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In vitro and in vivo response to nanotopographically-modified surfaces of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and polycaprolactone.
- 2006
-
In: Journal of Biomaterials Science, Polymer Edition. - : Informa UK Limited. - 0920-5063 .- 1568-5624. ; 17:12, s. 1405-23
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Journal article (peer-reviewed)abstract
- Colloidal lithography and embossing master are new techniques of producing nanotopography, which have been recently applied to improve tissue response to biomaterials by modifying the surface topography on a nano-scale dimension. A natural polyester (Biopol), 8% 3-hydroxyvalerate-component (D400G) and a conventional biodegradable polycaprolactone (PCL) were studied, both nanostructured and native forms, in vitro and in vivo. Nanopits (100-nm deep, 120-nm diameter) on the D400G surface were produced by the embossing master technique (Nano-D400G), while nanocylinders (160-nm height, 100-nm diameter) on the PCL surface were made by the colloidal lithography technique (Nano-PCL). L929 fibroblasts were seeded on polyesters, and cell proliferation, cytotoxic effect, synthetic and cytokine production were assessed after 72 h and 7 days. Then, under general anesthesia, 3 Sprague-Dawley rats received dorsal subcutaneous implants of nanostructured and native polyesters. At 1, 4 and 12 weeks the animals were pharmacologically euthanized and implants with surrounding tissue studied histologically and histomorphometrically. In vitro results showed significant differences between D400G and PCL in Interleukin-6 production at 72 h. At 7 days, significant (P
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| 8. |
- Malmsten, M, et al.
(author)
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Interfacial behaviour of 'new' poly(ethylene oxide)-containing copolymers
- 1999
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In: Journal of Biomaterials Science. Polymer Edition. - 0920-5063 .- 1568-5624. ; 10, s. 1075-1087
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Journal article (peer-reviewed)abstract
- Block copolymers containing poly(ethylene oxide) (PEO) have a wide applicability within biomedical applications, not the least due to anti-fouling properties of surface coatings based on these copolymers. We have investigated a number of these, and results for PEO/poly(butylene oxide) (PEO/PBO), PEO/poly(lactide) (PEO/PL), and PEO/poly(ethylene imine) (PEO/PEI) copolymers, as well as for PEO-esterified fatty acids, are presented and discussed. For the former class of polymers, the effects of molecular architecture on the adsorption properties are adressed, and experimental results obtained with ellipsometry and small-angle neutron scattering presented. For the PEO/PL block copolymers, the effects of the PEO and PL lengths for the polymer adsorption are adressed, as are the effects of degradation of the PL moiety on both adsorption and protein rejection. For the PEO-esterified fatty acids, the effects of PEO chain length and interfacial density on the protein rejection capacity of such coatings are discussed.
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| 9. |
- Nederberg, Fredrik, et al.
(author)
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Biocompatible and biodegradable phosphorylcholine ionomers with reduced protein adsorption and cell adhesion
- 2006
-
In: Journal of Biomaterials Science. Polymer Edition. - : Informa UK Limited. - 0920-5063 .- 1568-5624. ; 17:6, s. 605-614
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Journal article (peer-reviewed)abstract
- In this paper a recently developed biodegradable phosphorylcholine ionomer (PC ionomer) was evaluated in different biological environments with a focus on the adsorption of proteins (fibrinogen) and the adhesion of cells. Our results have shown that the polar phosphoryl choline (PC) group may be enriched at the surface of cast films with an added hydrophilic environment. X-ray photoelectron spectroscopy confirmed the surface depletion of PC groups in dry conditions, as nitrogen and phosphorous atoms were found in the bulk of the material but not at the outermost surface layer. The surface enrichment leads to a strongly hydrophilic surface that prevents the adsorption of proteins and reduces the adhesion of cells. The non-functional and hydrophobic reference poly(trimethylene carbonate) (PTMC) adsorbs both proteins and cells, thus the wetting and low adhesion behavior of the PC ionomer can be attributed to the introduced PC functionality. Since the in vivo acceptance of biomaterials is determined by their ability to withstand protein adsorption the PC ionomer described in this paper is highly interesting for a number of in vivo applications in which the adsorption of proteins may be critical, for example, blood contact events.
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| 10. |
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