Microwave plasma surface modification of silicone elastomer with allylamine for improvement of biocompatibility.

The microwave plasma surface modification of silicone elastomer with allylamine was studied to improve the biocompatibility of the material. An effort was made to clarify the relationships among plasma conditions and surface chemical composition, physical surface properties and biocompatibility of material, as well as the stability of plasma deposited layers. ATR-IR, XPS, Ellipsometry measurements, and contact angle measurements were used to investigate the changes of surface. The stability of plasma-treated silicone surfaces were also studied. The results demonstrated that the temperature and pressure had a strong influence on the chemical composition and structure of surface-deposited layer. The layer was nearly completely crosslinking when the modification was carried out at 60 degrees C. The polymerization speed decreased linearly with temperature. The XPS analysis results showed that the nitrogen element content in the surface layer was very high, especially under low pressure. The nitrogen/carbon ratio in the layer even greatly surpassed that of the allylamine monomer. The wettability of the silicone surface was greatly improved after plasma modification, and increased with the quantities of amine groups. The plasma-treated surfaces have good storage stability in air up to 3 months. The wettability of the surfaces decreased incipiently and then it dramatically increased with further time. The human skin fibroblasts were used to evaluate biocompatibility of plasma-treated silicone elastomer. The surface biocompatibility was greatly improved after modification; human skin fibroblasts adhered quickly and grew well on the modified silicone surface.

Membranes for biohybrid liver support: the behaviour of C3A hepatoblastoma cells is dependent on the composition of acrylonitrile copolymers.

Co-polymers based on acrylonitrile, N-vinylpyrrolidone, aminoethylmethacrylate and sodium methallylsulfonate were used to prepare flat membranes by phase inversion. The surface properties of membranes were characterised by water contact angle measurements, atomic force microscopy and X-ray photoelectron spectroscopy (XPS). Membrane permeability was estimated by porosity measurements with water as test liquid. Human C3A hepatoblastoma cells were plated on these materials. Cell-material interaction was characterised by overall cell morphology, formation of focal adhesion contacts and intercellular junctions. Furthermore, cell proliferation was measured and compared with the functional activity of cells as indicated by 7-ethoxycoumarin-O-deethylation. More hydrophilic materials reduced spreading of cells, formation of focal adhesion and subsequent proliferation while homotypic cell adhesion was facilitated in correlation with stronger expressions of intercellular junctions and improved functional activity. In contrast, membranes with stronger adhesivity enhanced cell proliferation but reduced the functional activity of cells. It was concluded that the co-polymerisation of acrylonitrile with hydrophilic co-monomers, such as N-vinylpyrrolidone, could be used to tailor membrane materials for the application in biohybrid liver support systems.

On the tissue compatibility of poly(ether imide) membranes: an in vitro study on their interaction with human dermal fibroblasts and keratinocytes.

Recently we have developed a novel type of membrane based on poly(ether imide) (PEI) which is considered for biomedical application. To improve its physical and biological performance it was modified by blending with poly(benzimidazole) (PBI). In the present study both membranes were characterized in terms of their physicochemical properties and in vitro tissue compatibility using human dermal fibroblasts and keratinocytes. The modified membrane (PEI*) was more hydrophilic, less porous and had an increased surface (zeta) potential. We further found that blending with PBI tends to promote cell contact, at least initially, as indicated by the improved overall cell morphology, adhesion and spreading of fibroblasts, and the development of focal adhesion complexes. The effects of fibronectin (FN) and serum coating were also beneficial when compared to pure PEI and tissue culture polystyrene (TCP), which correlates to a higher adsorption of both FN and vitronectin detected by ELISA. However, a clear tendency for homotypic cellular interaction particularly of keratinocytes was obtained in contact with membranes, which was much stronger pronounced on PEI*. Although the initial adhesion was greater on PEI*, a surprising decrease in cell growth was observed at later stages of incubation, which may be explained with the membrane-promoted cellular aggregation leading to an easier detachment from the substratum. Thus, membranes based on blends of PEI with PBI could provide a tissue compatible scaffold with lowered adhesive properties, which might be a useful tool for the transfer of cells, for example, to in vitro engineered tissue constructs.

The influence of the chemical composition of cell culture material on the growth and antibody production of hybridoma cells.

The multiplication and antibody production of murine hybridoma cells cultured on five different polymer membranes were tested and compared with conventional tissue culture polystyrene (TCPS). Membranes were prepared from polyacrylonitrile (PAN) and acrylonitrile copolymerized with N-vinylpyrrolidone (NVP20, NVP30), Na-methallylsulfonate (NaMAS) and N-(3-amino-propyl-methacrylamide-hydrochloride) (APMA). Cell number and antibody concentration were quantified as criteria for viability and productivity. Adhesion of hybridoma cells was characterized by vital and scanning electron microscopy. The results suggest that a strong adhesion of cells, observed on APMA and TCPS, increased cell growth but reduced monoclonal antibody production. In contrast membranes with lowered adhesivity such as NVP20 provided favourable conditions for monoclonal antibody production. In addition it was shown that this membrane also possessed a minor fouling as indicated by the low decrease of water flux across the membrane after protein adsorption. It was concluded that NVP20 could be a suitable material for the development of hollow fibre membranes for bioreactors.

Surface properties of and cell adhesion onto allylamine-plasma-coated polyethylenterephtalat membranes.

Allylamine was plasma polymerised onto a polyester (PET) membrane to obtain a surface with good cell adhesive properties. Samples were coated using a microwave plasma source operating at different process parameters. The effect of process parameters on the physical, and chemical properties of plasma-polymerised-allylamine (PPAa) was evaluated by studying elemental composition, amine concentration, wettability, and surface morphology. A relatively high amine concentration was measured (up to 50 nmol/cm2). In parallel, nitrogen enrichment was observed after exposure to high-energetic plasma. Irrespective of the treatment conditions, oxygen was incorporated into the polymer structure. PPAa surfaces were found to be more hydrophilic than PET. The wettability of the samples increased with increasing amine concentration. Pictures from scanning electron microscopy indicated that homogeneous pinhole-free PPAa layers were deposited on PET membranes, without a significant change of permeability. In vitro evaluation of biocompatibility was carried out by studying human skin fibroblast interaction with surfaces. Cell attachment and viability on PPAa layers were found to be more intensive than on the control PET, based on the higher metabolic activity of adhering cells, but also on morphological criteria including overall cell morphology.

Testing the cytotoxicity of metal alloys used as magnetic prosthetic devices.

Technical magnetic materials are increasingly used for the development of magnetic retained dental prosthetic and orofacial epithetic devices. Since most of the magnets based on rare earth metals, such as samarium-cobalt based alloys have a high tendency for corrosion they were first coated by tin and then encapsulated by titanium. However, the high mechanical load particularly on dental devices may cause a rupture of the titanium capsule and the alloys contact directly biological fluids. Hence, it is important to know the cytotoxicity of these magnets to assess their potential effects on the surrounding tissue. In this study, the cytotoxicity of neodymium-iron-boron and samarium-cobalt (plain, tin and titanium coated) magnets was tested. First, magnets were incubated up to 7 days in culture medium to prepare extracts for cytotoxicity measurements. Changes in the surface morphology due to corrosion were visualized by scanning electron microscopy and analysis of the elemental composition. 3T3 mouse fibroblasts were cultured in the presence of extracts and their viability measured by neutral red and metabolic assays. To learn more about a possible toxic activity of the main components of magnets, salt solutions of different concentrations resembling those elements, which are main constituents of the magnets, were used. 3T3 fibroblasts were also cultured in direct contact with the materials and material induced effects on cell morphology and growth monitored by microscopy. As a result of this study it was found that samarium-cobalt magnets have a strong tendency for corrosion and exert a considerable cytotoxicity. Neodymium-iron-boron magnets have a lesser tendency for corrosion and are only moderate cytotoxic. Coating of samarium-cobalt magnets with tin or titanium makes the materials non-toxic. Application of salt solutions shows that cobalt has a tendency to be cytotoxic at higher concentrations, but enhances cell metabolism and proliferation at lower concentrations while the other magnet constituents had a lower or negligible cytotoxic potential.