Surface Of Polyurethane Films Research Articles

Plasma treatment of polyurethane coating for improving endothelial cell growth and adhesion

The advantage of helium plasma treatment in enhancing endothelial cell growth and adhesion on polyurethane film coated on glass substrate is demonstrated with experimental data. Human coronary artery endothelial cell (HCAE) growth and attachment was studied on (1) bare glass substrate, used as control, (2) coated glass, with and without helium plasma treatment and (3) collagen-treated polyurethane-coated glass substrates. The untreated polyurethane film surface was rough (RMS = 690 nm) and highly hydrophobic (contact angle = 90°). Cell growth on the untreated polyurethane surface was poor (cell concentration ≈ 3750/cm2) compared to glass surface (cell concentration ≈ 17 665/cm2). The atmospheric helium plasma treatment of the polyurethane film resulted in oxidation of the surface, a slight increase in roughness (RMS = 735 nm) and a significant drop in hydrophobicity (contact angle = 79°). The critical surface tension (γ C) of polyurethane film was also increased by 2 dynes/cm due to helium plasma treatment. These changes resulted in enhanced HCAE cell growth in polyurethane film (cell concentration ≈ 16 230/cm2) compared to the untreated polyurethane film. The cell growth was also comparable to cell growth on a glass surface (17 665/cm2) and the collagen-treated polyurethane film surfaces (cell concentration ≈ 21 645/cm2), respectively. Moreover, the strength of cell attachment on a plasma-treated surface (cell retention R = 89%) under laminar flow was significantly higher than that on a glass surface (R = 71%). While the collagen-treated polyurethane surface had the highest number of HCAE cells, the cell adhesion was found to be poor (R = 42%) compared to that of a plasma-treated surface. Thus, the overall performance of the plasma-treated polyurethane film surface on endothelial cell growth was better than other substrates studied here.

Preparation and Properties of Crosslinked Polyurethane Containing Hydrophilic PEO Component for Biomaterials

A series of multiblock polyurethanes containing various poly(ethylene oxide) (PEO) contents (0-80 wt%) were prepared from hexamethylene diisocyanate (HDI)/ PEO / poly(tetramethylene oxide) (PTMO)/ polybutadiene diol (PBD)/ 1,4-butanediol (BD) and used as modifying additives (30 wt%) to improve the properties of biomedical grade PelletheneÒ. A hydrophilic PEO component was introduced by the addition of PEO-containing polyurethanes and dicumyl peroxide (DCP) as the crosslinking agents in a PelletheneÒ matrix. As the PEO content (PEO block length) increased, the hydrogen-bonding fraction of the crosslinked polyurethane also increased, indicating an increase in the phase separation with an increase in the PEO content in the crosslinked polyurethane. Using electron spectroscopy for a chemical analysis, the ratio of ether carbon to alkyl carbon in the crosslinked polyurethane film increased remarkably with an increase, in the PEO content. Meanwhile, the water contact angle of the crosslinked polyurethane film surfaces decreased with increasing PEO content. The water absorption and mechanical properties of the crosslinked polyurethane films increased with increasing and the platelet adhesion on the crosslinked polyurethane film surfaces decreased significantly. Accordingly, these results suggest that the crosslinked polyurethane containing a hydrophilic PEO component may be more effective for a biomaterial application that is in direct contact with blood.

Morphology and hydrophobicity of a polyurethane film molded on a porous anodic alumina template

Surface characteristics are so paramount that they invariably require surface modification to improve biocompatibility as biomaterials. We describe a method for modulating the morphology and corresponding hydrophobicity of a polyurethane (PU) using PU solution and a suitable porous anodic alumina (PAA) template. The film is characterized by optical microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and water contact angle measurements. The water contact angle on a molded PU film surface is approximately 152°, much bigger than that of 85° on a free surface formed in air. Super-hydrophobicity is due to the enhanced roughness, which is modulated by a well-designed PAA template surface morphology.

Imparting affinity sites for adenosine triphosphate on the surface of polyurethane through molecular imprinting

A simple methodology for imparting affinity sites for adenosine triphosphate (ATP) on the surface of polyurethane (PU) film is discussed. It is widely known that, through oxidation, a thin layer conjugated polymer can be coated onto many polymeric substrates. This possibility is explored in this report. 3-Amino phenyl boronic acid was polymerized in the presence of ATP as template using ammonium per sulfate. A thin layer of polyamino phenyl boronic acid was coated onto the surface of PU film immersed in the solution during the reaction. The coated layer showed remarkably high affinity toward ATP and equilibrium adsorption was attained rapidly in contrast to free standing molecularly imprinted polymers in which equilibrium adsorption is normally attained after several hours. The imprinted layer also showed a high degree of selectivity toward ATP compared to adenosine diphosphate (ADP). The approach is simple and affinity sites for any water soluble molecules can virtually be created on the surface of polymers of interest. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2088–2090, 2004

Platelet adhesion onto segmented polyurethane film surfaces modified by addition and crosslinking of PEO-containing block copolymers

Polyethylene oxide (PEO) surfaces were prepared by the addition of PEO-containing amphiphilic block copolymers as surface modifying additives and of dicumyl peroxide (DCP) as a crosslinking agent in segmented polyurethane (PU). PEO-polypropylene oxide-PEO triblock copolymers (Pluronics) with different PEO chain length (from 0 to 98) were used as the surface modifying additives. The PEO additives in the PU film were then crosslinked to be stably entrapped in the PU matrix. The crosslinking was done by free radicals produced from the decomposition of DCP in the film through heating (120°C) or ultraviolet irradiation (254 nm). The surface properties of the PEO additive-entrapped PU films were investigated by the measurement of water contact angles and electron spectroscopy for chemical analysis. The bulk properties such as water absorption, long-term film stability, and tensile strength and elongation at break, were also investigated. It was observed that addition of a small amount (5 wt% based on PU) of the PEO additives resulted in a considerable change of surface characteristics. The PEO additives were stably entrapped in the PU films by crosslinking of them, without significant changes of bulk properties of the films. From the platelet adhesion test on the prepared PEO additive-containing film surfaces, it was observed that the platelet adhesion on the surfaces decreases with increase in PEO chain length of PEO additives. The film surface containing additive with long PEO chains (chain length of 98) was particularly effective in preventing platelet adhesion. The crosslinking of the PEO additives in PU films did not affect the behavior of platelet adhesion on the surfaces; the films with crosslinked PEO additives showed similar platelet adhesion on the surfaces to the films with uncrosslinked ones.