Performance leakage for biospan-covered electrospun vascular stents in a pulsatile flow bioreactor

In-stent restenosis occurs in 15-20% of “simple” coronary lesions, and in 30-60% of patients with complex lesions. Covered-stents reduce the rates of in-stent restenosis by providing a membrane barrier which prevents late tissue ingrowth. In developing covered-stents it is vital to ensure that these novel stents are capable of enduring physiological conditions before implantation. This thesis focuses on quantifying the performance of polyurethane covered stents when placed under a variety of physiological and pathological conditions. Commercially available Ephesos coronary stents (4 mm diameter following inflation) were covered by electrospinning polyurethane onto a bare-metal stainless steel stents for 6, 8, and 10 minutes. The inflated polyurethane covered-stents were placed into a custom-modified Tissue Growth Technologies LumeGen bioreactor, which allows for independent control of key parameters of fluid flow, such as continuous vs. pulsatile f low, flow rate and pressure. The polyurethane covered-stents were exposed to various physiological and pathological conditions in a controlled setting focusing on flow rate, pressure, pulsatility, and amplitude of oscillation allowed as design criteria. The readout for the performance of these polyurethane stents was the fluid leakage as a function these various parameters. Our data showed no difference in leakage in terms of the duration of the electrospun coating, the fluid flow rate or the amplitude of the oscillations of the pulsatile flow. The leakage increased with increasing pressure, while increased fluid viscosity resulted in reduced leakage. These preliminary results indicate that electrospun polyurethane covered-stent can withstand significant physiological and pathophysiological fluid flow conditions. Such covered stents may find applications in reducing restenosis.M.S., Biomedical Engineering -- Drexel University, 201