title: Biodegradable injectable polyurethanes: synthesis and evaluation for orthopaedic applications.
abstract: Biodegradable polyurethanes offer advantages in the design of injectable or preformed scaffolds for tissue engineering and other medical implant applications. We have developed two-part injectable prepolymer systems (prepolymer A and B) consisting of lactic acid and glycolic acid based polyester star polyols, pentaerythritol (PE) and ethyl lysine diisocyanate (ELDI). This study reports on the formulation and properties of a series of cross linked polyurethanes specifically developed for orthopaedic applications. Prepolymer A was based on PE and ELDI. Polyester polyols (prepolymer B) were based on PE and dl-lactic acid (PEDLLA) or PE and glycolic acid (PEGA) with molecular weights 456 and 453, respectively. Several cross linked porous and non-porous polyurethanes were prepared by mixing and curing prepolymers A and B and their mechanical and thermal properties, in vitro (PBS/37 degrees C/pH 7.4) and in vivo (sheep bi-lateral) degradation evaluated. The effect of incorporating beta-tricalcium phosphate (beta-TCP, 5 microns, 10 wt.%) was also investigated. The cured polymers exhibited high compressive strength (100-190 MPa) and modulus (1600-2300 MPa). beta-TCP improved mechanical properties in PEDLLA based polyurethanes and retarded the onset of in vitro and in vivo degradation. Sheep study results demonstrated that the polymers in both injectable and precured forms did not cause any surgical difficulties or any adverse tissue response. Evidence of new bone growth and the gradual degradation of the polymers were observed with increased implant time up to 6 months.
authors.affiliation: PolyNovo Biomaterials Limited, Bayview Avenue, Clayton South 3169, Victoria, Australia. raju.a@polynovo.com
authors.forename: Raju
authors.initials: R
authors.lastname: Adhikari
authors.forename: Pathiraja A
authors.initials: PA
authors.lastname: Gunatillake
authors.forename: Ian
authors.initials: I
authors.lastname: Griffiths
authors.forename: Lisa
authors.initials: L
authors.lastname: Tatai
authors.forename: Malsha
authors.initials: M
authors.lastname: Wickramaratna
authors.forename: Shadi
authors.initials: S
authors.lastname: Houshyar
authors.forename: Tim
authors.initials: T
authors.lastname: Moore
authors.forename: Roshan T M
authors.initials: RT
authors.lastname: Mayadunne
authors.forename: John
authors.initials: J
authors.lastname: Field
authors.forename: Margaret
authors.initials: M
authors.lastname: McGee
authors.forename: Tania
authors.initials: T
authors.lastname: Carbone
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D006016:Glycolates / Q000737:chemistry / Q000378:metabolism; D020007:Implants, Experimental; D007267:Injections; D019344:Lactic Acid / Q000737:chemistry / Q000378:metabolism; D008422:Materials Testing; D009985:Orthopedics; D011140:Polyurethanes / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D012756:Sheep; D013499:Surface Properties; D023822:Tissue Engineering / Q000379:methods*
chemical_list: D001672:Biocompatible Materials; D006016:Glycolates; D011140:Polyurethanes; C031149:glycolic acid; D019344:Lactic Acid