title: In vivo biostability of polyether polyurethanes with polyethylene oxide surface-modifying end groups; resistance to biologic oxidation and stress cracking.
abstract: Polyethylene oxide (PEO) on polymer surfaces has been reported to reduce cellular adhesion, a very desirable property for cardiac pacing leads. A Shore 80A polyether polyurethane with up to 6% PEO surface-modifying end groups (SME) was evaluated for its chronic in vivo biostability. In a short-term (12 week) screening test, strained samples appeared to develop the same surface oxidation as unmodified polymer, but did not produce visible cracking > or =500x, prompting a longer-term study. By the time the longer-term study was initiated, most of the PEO SME had disappeared from the starting material's surface. After 1 year in vivo, surface oxidation, shallow surface cracking, and environmental stress cracking (ESC) developed on highly strained samples to the point of failure, so that there was no significant difference between the SME polymer and its control (the same polymer without SME). No further change was seen for up to 2 years of implantation. Unstrained PEO SME polymer developed shallow surface cracking, but no ESC up to 2 years of implantation. Thus, PEO SME slightly delayed, but did not stop biodegradation, and under unstrained conditions, has no adverse effect on biostability.
authors.affiliation: Medtronic, Inc., 7000 Central Avenue NE, Minneapolis, MN 55432, USA.
authors.forename: Mike
authors.initials: M
authors.lastname: Ebert
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: D020341:Absorbable Implants; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry*; D001673:Biodegradation, Environmental; D018786:Bone Substitutes / Q000737:chemistry; D002448:Cell Adhesion; D004987:Ethers / Q000737:chemistry*; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D008956:Models, Chemical; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry*; D011475:Prosthesis Failure; D011817:Rabbits; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D013997:Time Factors
chemical_list: D001672:Biocompatible Materials; D018786:Bone Substitutes; D004987:Ethers; D011108:Polymers; D011140:Polyurethanes; C115016:polyetherurethane; D011092:Polyethylene Glycols; D010100:Oxygen