Functional Elastomeric Scaffold Development for Tissue Engineering

Scaffolds for engineering soft tissue would ideally be mechanically compliant and anisotropic while possessing inherent bioactivity and enzyme sensitivity similar to the native extracellular matrix. Biodegradable elastomers, such as cytocompatible poly(ester urethane)ureas, represent attractive alternatives to more common biodegradable polyesters utilized in tissue engineering. These materials can be processed by electrospinning into scaffolds suitable for in vivo placement and support of cellular adhesion and growth. This process, where an electric field overcomes surface tension to generate and draw nanoscale fibers, can create scaffolds with extracellular matrix-like morphologies that retain mechanical strength and flexibility while also permitting protein incorporation into spun fibers to impart bioactivity. Poly(ester urethane)urea (PEUU) was blended with collagen or urinary bladder matrix and processed with electrospinning into nanofibrous scaffolds. Protein incorporation into the matrices resulted in increased cellular adhesion and scaffold degradation rate. PEUU scaffolds were fabricated with various degrees of fiber alignment to more closely mimic soft tissue anisotropy such as that of the native pulmonary valve. The fabrication of mechanically anisotropic scaffolds is desired due to their ability to direct cell growth during tissue remodeling. PEUU elastomeric matrices could serve as mechanical support scaffolds for cell adhesion and growth but can require long seeding and culture times to achieve high density cellular in-growth. Therefore, a microintegration technique was developed where the elastomeric fibers are spun concurrently with electrospraying of cells. This process produced viable, high cell density constructs and lessened the time necessary for scaffold fabrication and seeding. The functionality of electrospun PEUU was evaluated for its ability to release bioactive basic fibroblast growth factor or the antibiotic tetracycline. These controlled release elastomeric matrices might be appropriate for application in wound repair or management. Electrospun PEUU was also evaluated in fabricating a functional tissue engineered blood vessel. Small diameter electrospun PEUU tubular conduits were implanted as rat aorta replacements and demonstrated patency and tissue remodeling at 2 wks. In addition, the cellular microintegration technology was extended as a means to incorporate cells into electrospun small diameter tubes in vitro. These materials possessed mechanical compliance similar to native vessels and demonstrated great potential for tissue engineering