Synthesis and properties of photocross-linked poly(propylene fumarate) scaffolds

The photocross-linking of poly(propylene fumarate) (PPF) to form porous sca ffolds for bone tissue engineering applications was investigated. PPF was c ross-linked using the photoinitiator bis(2,4,6-trimethylbenzoyl) phenylphos phine oxide (BAPO) and exposure to 30 min of long wavelength ultraviolet (U V) light. The porous photocross-linked PPF scaffolds (6.5 mm diameter cylin ders) were synthesized by including a NaCl porogen (70, 80, and 90 wt% at c ross-linking) prior to photocross-linking. After UV exposure, the samples w ere placed in water to remove the soluble porogen, revealing the porous PPF scaffold. As porogen leaching has not been used often with cross-linked po lymers, and even more rarely with photoinitiated cross-linking, a study of the efficacy of this strategy and the properties of the resulting material was required. Results show that the inclusion of a porogen does not signifi cantly alter the photoinitiation process and the resulting scaffolds are ho mogeneously cross-linked throughout their diameter. It was also shown that porosity can be generally controlled by porogen content and that scaffolds synthesized with at least 80 wt% porogen possess an interconnected pore str ucture. Compressive mechanical testing showed scaffold strength to decrease with increasing porogen content. The strongest scaffolds with interconnect ed pores had an elastic modulus of 2.3 +/- 0.5 MPa and compressive strength at 1% yield of 0.11 +/- 0.02 MPa. This work has shown that a photocross-li nking/porogen leaching technique is a viable method to form porous scaffold s from photoinitiated materials.