title: Evaluation of thermal- and photo-crosslinked biodegradable poly(propylene fumarate)-based networks.
abstract: Biodegradable networks of poly(propylene fumarate) (PPF) and the crosslinking reagent poly(propylene fumarate)-diacrylate (PPF-DA) were prepared with thermal- and photo-initiator systems. Thermal-crosslinking was performed with benzoyl peroxide (BP), which is accelerated by N,N-dimethyl-p-toluidine (DMT) and enables injection and in situ polymerization. Photo-crosslinking was accomplished with bis(2,4,6-trimethylbenzoyl) phenylphosphine oxide (BAPO), which is activated by long-wavelength UV light and facilitates material processing with rapid manufacturing techniques, such as stereolithography. Networks were evaluated to assess the effects of the initiators and the PPF/PPF-DA double bond ratio on the mechanical properties. Regardless of the initiator system, the compressive properties of the PPF/PPF-DA networks increased as the double bond ratio decreased from 2 to 0.5. BAPO/UV-initiated networks were significantly stronger than those formed with BP/DMT. The compressive modulus of the photo- and thermal-crosslinked PPF/PPF-DA networks ranged from 310 +/- 25 to 1270 +/- 286 MPa and 75 +/- 8 to 332 +/- 89 MPa, respectively. The corresponding fracture strengths varied from 58 +/- 7 to 129 +/- 17 MPa and 31 +/- 13 to 105 +/- 12 MPa. The mechanical properties were not affected by the initiator concentration. Characterization of the network structures indicated that BAPO was a more efficient initiator for the crosslinking of PPF/PPF-DA, achieving a higher double bond conversion and crosslinking density than its BP counterpart. Estimated average molecular weights between crosslinks (Mc) confirmed the effects of the initiators and PPF/PPF-DA double bond ratio on the mechanical properties. This work demonstrates the capability to control the properties of PPF/PPF-DA networks as well as their versatility to be used as an injectable material or a prefabricated implant.
authors.affiliation: Department of Bioengineering, Rice University, 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: D001672:Biocompatible Materials; D001673:Biodegradation, Environmental; D002851:Chromatography, High Pressure Liquid; D005650:Fumarates / Q000737:chemistry*; D008422:Materials Testing; D010777:Photochemistry; D011126:Polypropylenes / Q000737:chemistry*; D013696:Temperature; D014466:Ultraviolet Rays
chemical_list: D001672:Biocompatible Materials; D005650:Fumarates; D011126:Polypropylenes; C097850:poly(propylene fumarate)