|Institution:||University of Rochester|
|Keywords:||Aspect ratio; Electrospinning; Membranes; Scaffolds; Surface modification; Modeling|
|Full text PDF:||http://hdl.handle.net/1802/29276|
Tissue engineering has been an active research area for several decades. Synthetic polymers and natural polymers, such as poly(ε-caprolactone) (PCL) and collagen, are promising materials for ongoing tissue engineering applications. However polymer materials suffer from weak mechanical properties. There are numerous publications that discuss materials reinforcement, but for electrospun membranes, very limited publications as yet have focused on it. My research seeks to develop a new approach for manufacturing reinforced composite electrospun membranes, building mechanical property modeling, and studying the fundamentals of electrospinning. </br> First, to improve the mechanical properties, novel PCL composites have been electrospun by incorporating Al₂O₃ whiskers as reinforcements. The results offer exceptional properties: The elastic modulus and ultimate tensile strength were significantly improved by the whisker reinforcements. The cell morphology and proliferation studies demonstrated that Al₂O₃ whisker- reinforced PCL scaffolds maintained good biocompatibility. To investigate new approaches for preparing composite scaffolds that have both high strength and high elasticity, the surface modified Al₂O₃/PCL scaffolds were fabricated by electrospinning. The results showed dramatically improved tensile strength, while elasticity remained with almost no decrease in that property. This finding indicates it is possible to obtain electrospun materials that have both high rigidity and high elasticity. The effect of the particle aspect ratio on the mechanical properties composites was also investigated. The composites exhibited a high modulus with higher aspect ratio reinforcements even at low content. Based on these experimental results and the application of conventional composite theory, an optimized mechanical property model for electrospun scaffolds was established. Further study shows that the tensile modulus of electrospun scaffolds was not sensitive to the reinforcement filler modulus; instead it depended more on the filler content and the aspect ratio. Lastly, the fundamental of beads formation in an aqueous electrospinning system was studied using Type I collagen/PBS/ethanol solvent systems. The formation of beads during the electrospinning of collagen was analyzed from a thermodynamics perspective. These results showed that if the kinetic parameters are carefully controlled, it is possible to gain/acquire smooth thin collagen fibers from a high water content system, despite the high driving force for bead formation.