Biomer films

Analytical Methods. A piece of Avcothane pump or Biomer film was pressed against a KRS-5 plate which was the internal reflection plate by applying maximum pressure to insure close contact by using a sample holder provided by the Wilkes model 9 attachment. As illustrated in Chart I, the incident angle was 60° and the polymer was pressed against only one side of the KRS-5 since the IR-absorption intensity was too... 

Figure 5. Difference reflection IR spectra of air surface of Biomer film with KRS-5 reflection plate (a) without a harrier film, (b) with a barrier film of...

Table II. Absorption Ratios of Biomer Film Surfaces (19)...

Figure 8. Surface chemical composition-depth profile of Biomer film. The calibrated soft-segment content in air surf ace / substrate surface. (O) Based on 1640 cm 1 (0) based on 1600 cm 1.

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). 

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. 

Jute (40%) PHB, (Biomer) Film stacking/ heating under vacuum 68 8.5 N.S. N.S. Plackett and Andersen (2002)... 

Anderson et al. [59, 75,76] have been pursuing their extensive researches on the biomedical behavior of PEUUs having various formulations modified with hydrophobic acrylate (or methacrylate) polymer or copolymer additives. The most distinguished additive was Methacrol 2138F, which is a copolymer between diisopropylaminoethyl methacrylate and decyl methacrylate [co(DIPAM/DM)] (in a 3-to-l ratio). The protein adsorption assay showed that PEUU (Biomer-type) films loaded or coated with Methacrol or poIy(DIPAM) adsorbed significantly lower amounts of human blood proteins (Fb, IgG, factor VIII, Hageman factor and Alb) than the base PEUU or PEUUs modified by other additives. It was revealed from their experiments that poly(DIPAM) as well as Methacrol exhibited a prominent suppressing effect on the protein adsorption process. 

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. 

The effectiveness of solvent extraction was evaluated by a lipid-doped polymer study. Selected lipids were dispersed in Biomer. Then, two sample films, one containing 1 mg, the other 10 mg of palmitic acid, cholesterol, and tripalmitin were cast from two consecutive castings each of 10% Biomer in dimethylacetamide (DMAC). Lipid concentrations of the 1-mg- and 10-mg-doped samples were calculated to be 0.1% and 1%, respectively. Following casting, a soxhlet extraction and quantitative analysis of extracted lipids were performed. The final extracted concentrations were compared with initial solution concentrations, resulting in an extraction efficiency ratio for each type of component. 

Prior to polymerization, the monomer solution was vacuum distilled, and purged with nitrogen. Square Biomer samples measuring 1.5 cm2, with average thicknesses of 0.6 mm, were cut from film cast from a 10% solution in DMAC. Each sample was preswelled in a monomer solution containing AIBN initiator. Samples were then transferred to a dilute aqueous solution of monomer, and were irradiated on both surfaces for 20 min with a 400 W mercury vapor lamp. The reaction vessel was purged with nitrogen and cooled with air. 

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. 

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... 

Bacterial PHBV (3HV content 12%, Mn = 336 000, Mw/Mn = 2,8) was supplied by Aldrich. Atactic PHB (a-PHB Mn = 13 000, Mw/Mn = 1,3) was synthesized via anionic ring opening polymerization of racemic P-butyrolactone initiated with the 18-crown-6-siq)ramolecular complexes of potassium hydroxide. Natural PHB was supplied by Biomer (Germany) and the fiction soluble in chloroform (Mn = 103 000, Mw/Mn = 5,2) was used for experiments.. The binary PHBV/a-PHB blends (contained 30 and 40 wt% of a-PHB, respectively), PHBV/PHB blend (70/30 wt%) as well as PHBV/PHB/a-PHB blend (50/25/25 wt%) were prepared by casting from chloroform solution on glass plates at room temperature. Films with thickness of 0,2-0,3 mm were obtained. The films of PHB and PHBV were prepared similarly. 

The prostheses consist of networks of fibrils of diameter approximately Ip, separated by pores of about lOp. Considerable melding occurs at the crossing points. Such structures have an enormous surface area, so that the results in Table 1 indicate a greater sensitivity to liquids than is found with other solid specimens (such as films) under similar conditions. It is apparent that hydrophilic vinyl monomers are strong swelling agents for Biomer and partially dissolve the polymer. This is particularly pronounced with acrylic acid which may ultimately be able to completely dissolve a prosthesis. 

The PHB was kindly presented by Biomer Co (Krailing, Germany) as lot 16F. The initial polymer was in the form of white powder with particle size 5-20 pm, MW = 2.06x 10 Da. Ultrathin fibers were obtained by electrospinning from 5 to 9% PHB chloroform solutions. The details of this procedure were described earlier in Ref [24]. Physical modifications of PHB structure were produced by cold rolling at 22 1°C at rolling rate 30 s and compression 200 kg/cm [25=22], As result of compression the film thickness decreased from 120 15 to 95 10 pm. 

Figure 7 Scanning electron micrographs of platelets adhered to PAS films (original magnification X 1000) The PDMS content in the PAS films is (A) 0 wt% (aramid homopolymer), (B) 25 wt%, (C) 53 wt%, (D) 75 wt%, (E) SILASTIC 500-1, (F) Biomer , (G) glass.

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