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  • 1
    Electronic Resource
    Electronic Resource
    Biological characterization of hydrogels of poly(vinyl alcohol) and hyaluronic acid (1994)
    Springer
    Journal of materials science 5 (1994), S. 613-616 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Hydrogels of hyaluronic acid (HA) and poly(vinyl alcohol) (PVA) were prepared using eight freezing-thawing cycles from HA/PVA blends (10/90, 20/80, 30/70, 40/60, 50/50, and 0/100 (w/w) ratios). The biocompatibility of the hydrogels was tested by means of in vitro cytotoxicity and cytocompatibility tests using cell culture techniques. The release with time of HA and PVA, the two hydrogel components, ion aqueous medium was also monitored and evaluated. The results indicate that all the hydrogels are not cytotoxic, while cell adhesion was very scarce in PVA and was not improved by the addition of HA. The release kinetics of HA and PVA from the hydrogels were different. After 2 h, HA percentages from about 80 (10/90 blend) to 100% (20/80, 40/60 blends) were released from the hydrogels into the aqueous medium. In contrast, the percentages of released PVA remain lower in time compared with HA, reaching a plateau after 24 h and ranging from a maximum of about 13% (0/100 blend) to a minimum of about 6% (10/90, and 20/80 blends).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00120341
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  • 2
    Electronic Resource
    Electronic Resource
    Optimization of the interaction between ethylenevinyl alcohol copolymers and human endothelial cells (1996)
    Springer
    Journal of materials science 7 (1996), S. 8-12 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: To better understand and optimize the fine interactions that occur during adhesion events between human cells and synthetic materials, we seeded human umbilical vein endothelial cells (HUVEC) onto ethylene-vinyl alcohol (EVOH) copolymer films prepared by casting. Different adhesive proteins, e.g. fibronectin and gelatin, and the monoclonal antibody (MoAb) CLB-HEC19 specific for the endothelial cell membrane were used to coat the materials. We used atomic force microscopy (AFM) to analyse the EVOH film structure, to test its planarity and homogeneity, before seeding it with endothelial cells. The metabolic changes induced in the endothelial cells by interactions with the copolymer functional groups and the adhesive proteins were monitored by a micro-electronic pH sensor, positioned close to the HUVEC monolayer. We found that the adhesion of HUVEC onto various substrates was finely modulated by the MoAb CLB-HEC19 and that the endothelial cell metabolic rate was enhanced when cultured onto a CLB-HEC19 coating. Surface roughness seems also to play a role in the interaction with HUVEC. The AFM measurement analysis demonstrated that L6 surface is rougher than R20. These surface characteristics could favour cell adhesion; in fact HUVEC adhesion results on R20 were significantly lower than on L6.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00121182
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  • 3
    Electronic Resource
    Electronic Resource
    Dehydro-thermally cross-linked collagen-poly(vinyl alcohol) blends: mechanical, biological and surface properties (1996)
    Springer
    Journal of materials science 7 (1996), S. 297-300 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: The mechanical, biological and surface properties of films, based on blends of soluble collagen and poly(vinyl alcohol), were investigated. Films prepared by casting were cross-linked by a dehydro-thermal treatment. The mechanical behaviour of the materials was studied by dynamic-mechanical thermal analysis. The biological properties of the films were evaluated by performing cytotoxicity and cytocompatibility in vitro tests. Surface characterization was carried out by X-ray electron spectroscopy. The results obtained indicate that these materials behave as two-phase systems and a remarkable enrichment of collagen in the surface with respect to the bulk was observed. Cytocompatibility tests show that the blending of the two polymers creates a better substrate for cell growth in comparison with pure components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00058570
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  • 4
    Electronic Resource
    Electronic Resource
    Hydrogels based on chitosan and dextran as potential drug delivery systems (1999)
    Springer
    Journal of materials science 10 (1999), S. 301-307 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The release of human growth hormone (GH) from bioartificial polymeric materials in the form of hydrogels, was measured in vitro for up to 3 weeks. Poly(vinyl-alcohol) (PVA) was blended, in different ratios, with two biological polymers, dextran and chitosan respectively. These blends were used to prepare hydrogels, using a freeze–thawing method. The hydrogels were loaded with GH, and their potential use as delivery systems was investigated. The release with time of PVA, in aqueous medium, was also monitored and evaluated. Scanning electron microscopy was used to investigate the structure of the hydrogels. The results obtained indicated that GH can be released from both dextran/PVA and chitosan/PVA hydrogels. The initial GH concentration used for sample loading affected the total quantity of GH released but not the pattern of release. The amount of GH released was affected by the content of the biological component. The percentage of PVA released was low but it was, however, related to the content of chitosan and dextran in the blends. ©1999 Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008961614439
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  • 5
    Electronic Resource
    Electronic Resource
    Poly(ester-ether-ester) block copolymers as biomaterials (1994)
    Springer
    Journal of materials science 5 (1994), S. 33-39 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Poly(ester-ether-ester) block copolymers, belonging to a class of biodegradable materials, were synthesized from poly(ethylene glycol) and ε-caprolactone by a simple ring-opening mechanism, which avoids the use of potentially toxic inorganic or organometallic initiators. The morphological and mechanical properties of such materials were investigated by gelpermeation chromatography, vapour pressure osmometry, proton magnetic resonance, infrared spectroscopy, differential scanning calorimetry, X-ray diffractometry and stress-strain tensile tests. The biocompatibility was investigated by cytotoxicity and hemocompatibility tests; the cytotoxicity was tested by the Neutral Red uptake assay, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, the Kenacid Blue R-binding method, and by the cell proliferation test on polymer films; the hemocompatibility was tested by the contact activation both of the coagulation cascade (intrinsic pathway), by the plasma prekallikrein activation test, and of the thrombocytes, by measuring the release of platelet factor 4 and β-thromboglobulin. The experimental results show that such a polymerization process permits high-molecular mass block copolymers with relatively good tensile and mechanical properties to be obtained. Their cyto- and hemo-compatibility makes them suitable for employment as biomaterials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00121151
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of chitosan and dextran on the properties of poly(vinyl alcohol) hydrogels (1999)
    Springer
    Journal of materials science 10 (1999), S. 431-435 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Hydrogels are three-dimensional polymeric networks very similar to biological tissues and potentially useful as drug delivery systems. Poly(vinyl alcohol)-based hydrogels containing different amounts of dextran or chitosan were prepared using the freezing–thawing method. Repeated freezing–thawing cycles of a poly(vinyl alcohol) (PVA) aqueous solution lead to the formation of crystallites which act as cross-linking sites, and a hydrogel with a high capacity to swell is obtained. The effects of the two different polysaccharides on the properties of the obtained materials were investigated by differential scanning calorimetry, dynamic mechanical analysis and scanning electron microscopy. In addition the release with time of poly(vinyl alcohol) in aqueous medium, was monitored and evaluated. On the basis of the obtained results it seems that the presence of dextran favors the crystallization process of PVA, allowing the formation of a more ordered and homogeneous structure. Instead, chitosan seems to perturb the formation of PVA crystallites leading to a material with a less regular structure. © 1999 Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008983215833
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  • 7
    Electronic Resource
    Electronic Resource
    Physico-chemical and mechanical characterization of hydrogels of poly (vinyl alcohol) and hyaluronic acid (1994)
    Springer
    Journal of materials science 5 (1994), S. 862-867 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Hydrogels are three-dimensional polymeric networks very similar to biological tissues and potentially useful as soft tissue substitutes and drug delivery systems. Many synthetic polymers can be used to make hydrogels: poly (vinyl alcohol) is widely employed to make hydrogels for biomedical applications. Improvements in the biocompatibility characteristics of synthetic materials could be achieved by the addition of biological macromolecules. The resulting materials named “bioartificial polymeric materials” could possess the good mechanical properties of the synthetic component and adequate biocompatibility due to the biological component. We have used poly (vinyl alcohol) to make hydrogels containing various amounts of hyaluronic acid. These bioartificial materials were studied to investigate the effect of the presence of the hyaluronic acid on the structural properties of the hydrogels. Thermal, mechanical, morphological and X-ray analyses were performed. A close correspondence between the network consistency and the degree of crystallinity developed in the matrix suggested that the hyaluronic acid, when its content is about 20%, could provide heterogeneous crystallization nuclei for poly (vinyl alcohol) thus increasing the crystallization degree, and consequently, the storage modulus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01172026
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  • 8
    Electronic Resource
    Electronic Resource
    In vitro biocompatibility of fluorinated polyurethanes (1994)
    Springer
    Journal of materials science 5 (1994), S. 452-456 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: The in vitro biocompatibility of fluorinated polyurethanes (FPUs), labelled as FPU 42, 52, 58, and 60, was evaluated by means of thrombogenicity, cytoxicity and cytocompatibility tests. Cardiothane® was taken as control material. The thrombogenicity was tested on thin material films by measuring the activation of prekallikrein (PKK) to kallikrein (KK). Level I cytoxicity tests of the bulk materials, i.e. Neutral Red (NR) uptake, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), and Kenacid Blue (KB) assays, were performed to assess the influence of the polymer extracts on, respectively, lysosomes, mitochondria and cell proliferation. The cytocompatibility was evaluated, on thin membranes made by a spraying phase-inversion process, by measuring the area of the polymer surface covered by human umbilical vein endothelial cells (HUVEC) 1 week after seeding. The results indicate that all the polymers are not thrombogenic, and not cytotoxic. The FPUs that contain polycaprolactone glycol (PCLG) (FPU 52 and 60) instead of poly (tetramethylene ether) glycol (PTMEG) (FPU 42 and 58) as soft segment show the lowest thrombogenicity and the best cytocompatibility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00058982
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  • 9
    Electronic Resource
    Electronic Resource
    Evaluation of poly(vinyl alcohol) hydrogels as a component of hybrid artificial tissues (1995)
    Springer
    Journal of materials science 6 (1995), S. 71-75 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Hydrogels are three-dimensional polymeric networks very similar to biological tissues. Many synthetic polymers can be used in preparing hydrogels. Among them poly(vinyl alcohol) (PVA), physically crosslinked by repeated freeze-thawing cycles of polymer aqueous solutions, is widely employed to make hydrogels for biomedical applications. To increase the similarity between hydrogels and natural tissues and to obtain “polymeric hybrid tissues”, we attempted to incorporate 3T3 cells, from a mouse fibroblast cell line, into PVA hydrogels obtained by one freeze-thawing cycle using as a solvent complete culture medium. Hydrogels were also made using eight freeze-thawing cycles from PVA solutions prepared using as a solvent either complete culture medium or water. Cell adhesion experiments were performed by seeding 3T3 and human umbilical vein endothelial cells (HUVEC) on to the hydrogel surface. The effect of the solvent and of the different number of freeze-thawing cycles on the mechanical characteristics of the PVA hydrogels were investigated by dynamic-mechanical techniques. A scanning force microscope analysis of the hydrogel surface viscoelastic properties was also carried out. Our results show that PVA is not cytotoxic. Although PVA hydrogel surface characteristics do not seem to favour the adhesion of substrate-dependent cells, encouraging results were obtained with the 3T3 cells incorporation. DMA analysis indicates that the networks prepared by eight freeze-thawing cycles possess a mechanical consistency comparable, even slightly better, than the ones prepared by only one freeze-thawing cycle and used for the cell incorporation studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00120410
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  • 10
    Electronic Resource
    Electronic Resource
    Cell cultures in the biocompatibility study of synthetic materials (1993)
    Springer
    Cytotechnology 11 (1993), S. S137 
    Details
    ISSN: 1573-0778
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In vitro cytotoxicity (Neutral Red uptake, Kenacid Blue and MTT) and cytocompatibility (cell adhesion and proliferation) tests were applied to the biocompatibility study of a series of poly(ester-ether-ester) block copolymers of potential interest as biomaterials. Our results indicate that the copolymer extracts after 72 hours incubation with a 3T3 mouse fibroblast cell line do not induce significant toxic effects. Furthermore, human umbilical vein endothelial cells seeded on thin copolymer films show a normal pattern of growth. We conclude that thein vitro tests used are a valid instrument to evaluate the potential toxic action of synthetic materials on different cell compartments and that the tested materials seem to be promising for future applications in the field of biomedical devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00746079
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