title: In vivo biostability of polyether polyurethanes with fluoropolymer surface modifying endgroups: resistance to biologic oxidation and stress cracking.
abstract: A series of Shore 80A polyether polyurethanes were synthesized with from 0 to 6% fluoropolymer surface modifying endgroups (SME) to provide the bulk properties of the polyurethane with the surface properties of the fluoropolymer. It was theorized that the fluoropolymer would migrate to the surface, forming a monolayer barrier to the oxidants and crack-driving agents released by macrophages and foreign body giant cells in vivo. In a 12-week biostability screening test, samples strained to 400% elongation appeared to be highly stable. In a longer-term study, the fluoropolymer SME significantly delayed, but did not completely prevent the onset of microcracking and the development of environmental stress cracking in strained samples. Even so, the 4 and 6% SME polymers explanted at 2 years performed significantly better than the control. FTIR analysis did not correlate with SME concentration, but increased hydrogen-bonding index and loss of aliphatic ether (autoxidation) did correlate with the visual appearance and density of microcracks. Significant molecular weight reductions were seen for the SME-free control, but were small (within instrumental error) for the polymers with SME. The use of fluoropolymer as a SME does appear to be warranted as a means to improve polyether polyurethane biostability.
authors.affiliation: The Polymer Technology Group, 2810 7th St, Berkeley, California 94710, USA.
authors.forename: Bob
authors.initials: B
authors.lastname: Ward
authors.forename: James
authors.initials: J
authors.lastname: Anderson
authors.forename: Rick
authors.initials: R
authors.lastname: McVenes
authors.forename: Ken
authors.initials: K
authors.lastname: Stokes
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D005549:Foreign-Body Reaction / Q000473:pathology*; D015743:Giant Cells, Foreign-Body / Q000473:pathology*; D008422:Materials Testing / Q000379:methods; D010084:Oxidation-Reduction; D011140:Polyurethanes; D011817:Rabbits; D013314:Stress, Mechanical; D013997:Time Factors
chemical_list: D001672:Biocompatible Materials; D011140:Polyurethanes