290168 Fabrication of Strong, Porous Psed Scaffolds for Applications in Soft Tissue Engineering

Monday, October 29, 2012
Hall B (Convention Center )
Lisa Volpatti, Department of Chemical Engineering, University of Pittsburgh, Pittsburgh, PA and Yadong Wang, Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA

Background: Tissue engineering is a relatively new and rapidly growing area of biomedical engineering focused on the repair of defective or damaged tissues and organs in lieu of conventional organ transplants. Within this field, synthetic polymers are often used to create porous scaffolds that promote tissue regeneration. Poly(glycerol sebacate) (PGS) has been shown to possess the necessary qualities for soft tissue engineering applications as a biocompatible and rapidly degradable elastomer. Furthermore, PGS scaffolds have successfully been used to promote arterial tissue regeneration with no scar tissue formation. However, the current standard method of fabrication, salt leaching, creates scaffolds that lack the strength and suturability necessary for implantation due to their inadequate interconnectivity. A new fabrication method would be highly desirable in order to create strong, porous scaffolds from pure PGS.

Objective: To use thermally induced phase separation (TIPS) to create PSeD (poly(sebacoyl diglyceride), a linear subset of PGS) scaffolds with a network of interconnected pores. TIPS is a fabrication technique based on the thermodynamic principle that a homogeneous polymer solution at elevated temperatures can be converted into two phases, one polymer-rich and one polymer-lean, via the removal of thermal energy. Since PSeD has a high molecular weight and low polydispersity, it is likely to create an interconnected, porous structure during phase separation which would produce a stronger scaffold. The main objective of this project is to answer the question: Can thermally induced phase separation create porous PSeD scaffolds that are stronger than their salt leached counterparts to increase their applicability to soft tissue engineering?

Preliminary Results: TIPS was successfully employed using a ternary system of PSeD, dioxane, and water in an 87:13 volume dioxane to volume water ratio. Morphology was determined as a function of PSeD concentration (3, 5, or 7% by weight), cooling time (0, 30, 60, or 120 min), and cooling temperature (4ºC or 22.5ºC) before freezing the system at -80ºC. Scanning electron micrographs showed that scaffolds containing 3% polymer exhibit a fiber-like morphology, while those containing 5 or 7% PSeD have a more globular structure. The average pore size of the scaffolds increases from 1 µm to 15 µm with longer coarsening times. Coarsening temperature was not a significant factor in determining pore size.

Conclusion: PSeD scaffolds with tunable morphology can be successfully fabricated using TIPS. By varying parameters such as the polymer concentration and coarsening time, scaffolds with different pore sizes can be attained for different applications in soft tissue engineering. Future work includes determining the scaffolds’ strength and elasticity by mechanical testing and determining interconnectivity by Micro CT. Applicability to soft tissue engineering will be assessed by implantation in a rat abdominal aorta model, a procedure which is commonly performed in our lab.

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