Fabrication of burst pressure competent vascular grafts via electrospinning: effects of microstructure

In this work, electrospun tubes of interest for vascular tissue engineering were fabricated and evaluated for burst pressure and suture retention strength (SRS) in the same context as tensile strength providing a direct, novel comparison. Tubes could be fabricated displaying average burst pressures up to 4000 mmHg--well above the standard of 2000 mmHg--and SRS values matching those of relevant natural tissues. Surprisingly, highly oriented fiber and maximal tensile properties are not absolutely necessary to attain clinically adequate burst pressures. The ability to resist bursting is clearly related to both initial solution solids loading and electrospinning deposition time. We make novel in situ observations of the relative microstructural characteristics of failure during bursting, and connect this to the conditions used to fabricate the graft. Processes typically thought to promote fiber alignment are, in fact, highly condition-dependent and do not always provide superior properties. In fact, electrospun structures displaying no discernable alignment could achieve burst pressures regarded clinically sufficient. The properties of individual electrospun fiber clearly do not fully dictate macroscale properties. Normal background levels of point bonding are enhanced by increased rotational speeds, and can have effects on properties more dominant than those of alignment.