Polyurethane biomer

In this study we have attempted to investigate the effective chemical composition at the surfaces of two commercially available polyurethanes, Biomer and Avcothane, with the objective of identifying chemical species which would interact with plasma proteins. 

The distribution of albumin on the alkylated polymer surface was visualized for a polyether polyurethane. Using a double antibody technique, it was possible to uncover the dense, homogenous nature of the albumin adsorbate on the alkylated surface, and on controls, the patchy coverage with apparent albumin aggregates (Fig. 9) ( 3) Incubation of polyurethane (Biomer) 3 3 alkylated... 

Formation of (a) Aromatic Polyurethane, Pellethane, (b) Aromatic Polyurethane Biomer, and (c) Aliphatic Polyurethane Tecoflex... 

Although ATR has been used to quantify the variation in composition at the surface in TPEs (Sung and Hu, 1980), a related utility is its ability to monitor in situ processes such as reaction injection molding (RIM) (Ishida and Scott, 1986) and protein adsorption onto a polyurethane substrate (Pitt and Cooper, 1986). In the latter, the effect of shear rate on the kinetics of protein adsorption and desorption from phosphate-buffered saline (PBS) was studied in a specially designed flow cell. A very thin film of the commercial MDI-ED-PTMO polyurethane Biomer was cast from solution onto a Ge ATR prism. The thickness of the film was less than the penetration depth so the protein concentration could be monitored after the infrared absorption of the polymer... 

The materials selected for evaluation included three materials currently being used in these applications Biomer (Thoratec Laboratories Corporation, Emeryville, CA), representative of segmented ether-type polyurethanes Avcothane-51 (Avco Everett Research Laboratory, Inc., Everett, MA), a block copolymer of 10% silicone rubber and 90% polyurethane and Hexsyn (Goodyear Tire and Rubber Company, Akron, OH), a sulfur vulcanized hydrocarbon rubber that is essentially a polyhexene. Also selected, because of their easy availability, were Pellethane (Upjohn Company, North Haven, CT), an ether-type of polyurethane capable of being extruded in sheet form, and a butyl rubber formulation, compounded and molded at the National Bureau of Standards. The material thickness varied, but the sheets were generally about 1 mm thick. 

In this study, we have attempted to obtain a detailed, quantitative estimate of the surface chemical composition of two commercially available polyurethanes, i.e., Biomer and Avcothane, which have demonstrated a reasonable degree of blood compatibility. For example, Avcothane has been used as an intraaortic balloon pump for post-operative patients (5). Biomer also has been successfully used for artificial heart components in calves (14). 

Solutions of Biomer were obtained from Ethicon Inc. Biomer is poly (ether polyurethane) which contains urea linkage in the hard segment according to our IR analysis (19). Films of Biomer were cast on clean glass plates by diluting the polymer solution in dimethyl acetyl-amide. The films were dried in a vacuum oven at 50°C for 24 hr. The final film thickness was around 125/a. GPC analysis showed that the content of oligomers in Biomer was also negligible. Kel-F82, which is a copolymer composed of chlorotrifluoroethylene (97%) and vinylidene fluoride (3% ), was obtained from the 3M Company. 

In Avcothane and Biomer, the exact concentration of CH2 is not known. However, in a similar polyurethane made of 2 1 1 molar ratio of 2,4-toluene diisocyanate/ethylenediamine/polyether (mol wt 1000), our calculation shows that the actual depth can approach the predicted value if care is taken to insure close contact. Therefore, we would assume, for the sake of argument, that in Avcothane and Biomer our actual values approach the predicted values. 

In Biomer films, only a modest increase in the relative soft-segment concentration in the air side in comparison with the substrate side was observed when one studies the depth-concentration profile. In other polyurethanes which are similar to Biomer, Lyman and co-workers recently observed that the amount of polyether in the air-facing surface is approximately the same as in the glass-facing side, even though higher concentrations of polyether were found in both surfaces than in bulk (6). 

Biomer [Johnson Johnson]. TMfora unique type of polyurethane used in heart implants. 

Third, polyurethanes based on PTMO (Biomer, SPU 24, SPU 25, and SPU 26) tend to cluster with values of p from 0.28 to 0.42 (excluding the crystalline PTMO in SPU 24), whereas polyurethanes based on PPO are in a cluster with p ranging from about 0.1 to 0.32. Among PEO-containing segmented polyurethanes, the value of p ranges from 0.05 (SPU 51) to about 0.2. 

Materials evaluated in the 20-week in vitro study included Pellethane 2300 Series polyurethane (Upjohn, Inc.), polyphosphazenes PNF-200 and 200M (Firestone Co.), polyHexene-H (Goodrich, Inc.), and Biomer (Ethicon, Inc.). Biomer film was cast from a 10% solution in N,AU-dimethylacetamide (Aldrich) on a glass plate at 60°C. Samples were cut into Vi in. X 6 in. strips, with thicknesses measuring approximately 0.6 mm. Prior to exposure, samples were cleansed with a 1% Triton X-100 (Polysciences, Inc.) solution and rinsed with distilled water. They were then vacuum dried for 25 h, and weighed before exposure commenced. 

The mechanism for in vivo free LCFA deposition onto the polyurethane surface may result from a competitive desorption of albumin-bound LCFA s onto the lipophilic polymer soft segments. Albumin can carry upwards of 36 LCFA molecules (22), and Biomer has been shown to adsorb preferentially albumin during blood contact. 

Many polyurethenes for biomedical applications are available from commercial manufacturers (see Table A.2) Biomer (Ethicon) is composed primarily of methylenediphenylenediisocyanate, ED, and PTMO (2 1 1), see [42] Biomer and Pellethane were used in the artificial-heart program at the University of Utah. Medtronics produces polyurethanes Biostable C-19 and Biostable C-36 using cyclohexane-1,4-diisocyanate, 1,6-hexanediol, and soft segments with 18 or 36 carbons. 

Wabers, H.D., et al., Biostability and blood-contacting properties of sulfonate grafted polyurethane and Biomer. Journal of Biomaterial Science Polymer Edition, 1992, 4, 107-133. 

Germanium ATR crystals were coated with thin polymer films by spin-coating techniques. A commercially available spin coater (Headway Research, Inc., Model EC-101) with a specially designed Teflon chuck was used to hold the Ge crystal. For example, Biomer--the medical polyurethane supplied by Ethicon (Somerville, NJ)--was applied in three to four coats in a 1.5 percent solution of cyclohexanone to produce stable films with thickness less than the depth of penetration of the IR field. 

After drying for 15 h in vacuo, polyurethanes were compression moulded at temperatures between 100 and 200 C and at a nominal load of either 8 or 12 tons. Biomer" was solvent cast in 3 layers directly from the 30% dimethylacetamide solution supplied and the sheets were dried at 40 C in a flow of dry nitrogen for 7 days. The flat sheets had dimensions of 60 mm x 100 mm and were 1 mm thick. They were cut into several pieces or punched into dumbbells 3 cm in length. The straight (testing) area of the dumbbell was 13 nun x 4 mm. All samples showed no birefringence under cross polarizers, indicating that there was no detectable residual stress. 

This TPE is a segmented polyurethane and is reported to be not significantly different from biomer in chemistry and molecular weight. It is a polytetra-methyleneoxide-based aromatic polyurethane urea with mixed aliphatic and cycloaliphatic diamine chain extenders. A copolymer of... 

Available as a dimethyl acetamide solution, this segmented, aromatic, polycarbonate-based TPE polyurethane was designed to mimic Ethicon Corporation s Biomer. The polymer is made from the addition of diphenylmethane 4,4 -diisocyanate to a polycarbonate diol followed by addition of a mixture of chain extenders and a molecular weight regulator. The polymer is believed to be resistant to environmental stress cracking such as that experienced by other polyurethanes coated onto pacemaker leads (Tables 4.4, 4.12, and 4.13). 

Biomer (trade name of Ethicon, USA). Believed to be primarily a segmented block copolymer of polytetramethylene oxide (PTMO)/MDI/ethylene diamine. Available as either a 30 wt% solution or as an extruded grade. A new type is a copolymer of polyurethane with hydroxy-terminated polydimethyl siloxane (PDMS) (Fig. 13.15). 

Rimplast (Trade name of Petrarch Systems, USA). These are a series of IPN blends of high molecular weight silicone rubber with polyurethane. Toyoho (Trade name of Toyobo, Japan). A series similar to those of Biomer. Transparent PU elastomers. These are based on aliphatic diisocyanates and used for artificial organs. Compatibility with blood is achieved through either the incorporation of polysiloxane or surface treatment of the PU with heparin or albumen. 

Tyler BJ, Rattier BD. Variations between biomer lots. 2 The effect of differences between lots on in vitro enzymatic and oxidative degradation of a commercial polyurethane. J Biomed Mater Res 1993 27 327-34. 

Py-LVEIMS and PyHRMS were used in the determination of structure and composition of clinically important polyurethanes, PEUUs (Biomer, Lycra Spandex, Tecoflex and Pellethane) [746]. The antioxidants found in Biomer and Lycra Spandex were identified as well as an AO in Pellethane and an antistatic agent or residual catalyst in Biomer and Lycra Spandex. These tools are valuable for QC of implant material. PyMS is widely used in quality control of industrial products, such as foils and packaging materials [747], silicone and nitrile rubbers [748], can coatings and rubber sealing and tobacco [749]. In particular, it appears that Py-FIMS finds application not only for research in structure determination of non-volatile polymers, but also in product control. Schulten et al. [692] have described the application of Py-FIMS to paints (commercial can coatings), epoxy and polyester resins. Polyamides, acrylic and methacrylic resins, have been analysed in the same way [750-753], Py-FIMS is well suited for these investigations and allows identification of different polymer sub-units, such as monomers, dimers, backbone fragments, etc. Moreover, the technique enables differentiation of the examined compounds, which is of interest to industrial quality control. 

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