title: In vitro degradation of polymeric networks of poly(propylene fumarate) and the crosslinking macromer poly(propylene fumarate)-diacrylate.
abstract: Polymeric networks of poly(propylene fumarate) (PPF) crosslinked with poly(propylene fumarate)-diacrylate (PPF-DA) are currently being investigated as an injectable, biodegradable bone cement. This study examined the effect of crosslinking density, medium pH, and the incorporation of a beta-tricalcium phosphate (beta-TCP) filler on the in vitro degradation of PPF/PPF-DA. Cylindrical specimens were submerged in buffered saline at 37 degrees C and the change in weight, geometry, and compressive mechanical properties were monitored over a 52-week period. All formulations showed an initial increase in modulus and yield strength over the first 12 weeks, achieving maxima of 1307+/-101 and 51+/-3MPa, respectively, for the beta-TCP composite. PPF/PPF-DA networks with the lower crosslinking density demonstrated the greatest degradation with a 17% mass loss. Samples in the lower buffer pH 5.0 compared to physiological pH 7.4 did not show any differences in mass loss, but exhibited a faster decrease in the compressive strength over time. The beta-TCP composites maintained their mechanical properties at the level following their initial increase. These results show that the degradation of PPF/PPF-DA networks can be controlled by the crosslinking density, accelerated at a lower pH, and prolonged with the incorporation of the beta-TCP filler.
authors.affiliation: Department of Bioengineering, Institute of Biosciences and Bioengineering, Rice University, P.O. Box 1892, MS-142, Houston, TX 77251-1892, USA.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Timmer
authors.forename: Catherine G
authors.initials: CG
authors.lastname: Ambrose
authors.forename: Antonios G
authors.initials: AG
authors.lastname: Mikos
mesh_terms: D000179:Acrylates / Q000737:chemistry* / Q000378:metabolism; D001672:Biocompatible Materials; D001843:Bone Cements / Q000737:chemistry / Q000378:metabolism; D019245:Compressive Strength; D003432:Cross-Linking Reagents / Q000737:chemistry* / Q000378:metabolism; D005650:Fumarates / Q000737:chemistry* / Q000378:metabolism; D008422:Materials Testing; D011108:Polymers / Q000737:chemistry / Q000378:metabolism; D011126:Polypropylenes / Q000737:chemistry* / Q000378:metabolism
chemical_list: D000179:Acrylates; D001672:Biocompatible Materials; D001843:Bone Cements; D003432:Cross-Linking Reagents; D005650:Fumarates; D011108:Polymers; D011126:Polypropylenes; C097850:poly(propylene fumarate)