Characterization of electrospun polymer fibers for applications in cardiac tissue engineering and regenerative medicine

Electrospinning is a technique where a polymer solution is formed into a non-woven mat by electrically charging the solution as it leaves a capillary. The resulting mats have an interconnected porous network, and the system can be tailored in order to form aligned fibers. In this work, we have chosen to electrospin and characterize two polymers with unique properties with the intention to use them as scaffolds for cardiac tissue.; The first polymer studied was poly(N-isopropyl acrylamide) (pNIPAM), a material which shows a thermoresponsive behavior around 32°C in aqueous solutions. In this work, pNIPAM was electrospun into fibrous mats from three solvents and the resulting electrospun mats were evaluated using DSC, polarized Raman, and infrared spectroscopy and compared to the bulk material. It was found that the electrospinning process did not alter the polymer and pNIPAM maintained its thermoresponsive behavior. Therefore, it is believed that electrospun pNIPAM mats could have the potential to be used as templates or filters in aqueous solutions at high temperatures, above 32°C, and then removed by lowering the temperature.; The next polymer to be investigated was a biodegradable polyurethane (PU). The PU was electrospun into isotropic mats (ES-PU) and the material properties were evaluated via GPC, DSC, and Raman spectroscopy before and after processing. These analyses showed that the polymer was also unaffected by the electrospinning process. Additionally, the degradation profile of ES-PU in the presence of chymotrypsin was assessed. It was concluded that ES-PU mats show potential for use in soft tissue engineering applications.; Therefore, the next step in this research was to investigate the ability of ES-PU mats to support cardiac cells and direct tissuegenesis. Cells isolated from immature cardiac ventricles were grown on ES-PU mats with either aligned or unaligned microfibers. ES-PU cultures contained electrically-coupled, contractile myocytes and it was shown that fiber orientation influenced multi-cellular organization. Atrial natriuretic peptide (ANP) expression was significantly lower in cells grown on aligned scaffolds versus those grown on either isotropic ES-PU or on TCPS controls indicating that scaffold-imposed alignment resulted in a more mature cell phenotype. Therefore, it was concluded that the physical organization of ES-PU microfibers influences both multi-cellular form and cardiac cell function in vitro.