Development of biodegradable polyurethane electrospun small-diameter vascular grafts

F. MONTINI BALLARIN; P.C. CARACCIOLO; P.M. FRONTINI; G.A. ABRAHAM

Viña del Mar

Taller; 3º Taller de Órganos Artificiales, Biomateriales e Ingeniería de Tejidos, OBI 2013; 2013

Soc. Latinoamericana de Biomateriales, Organos Artificiales e Ing. de Tejidos

Small diameter vascular grafts for cardiovascular applications are still a challenge. Either because of supply, dimensions (autografts); immunogenic response (allografts and xenografts); thrombosis, stenosis and occlusion (synthetic grafts), the actual offer presents limitations. The existing synthetic alternatives fail mostly due to a biomechanical mismatch. It was found that the graft compliance plays a key role in their success. Natural arteries have a unique structure; composed of three layers, each one with a particular physiological role. The media, formed in its majority of elastin, gives the blood vessel its ability to contract and relax as a response to an external stimulus. The vascular grafts triumph lies in being able to mimic this unique behavior. The most common synthetic biodegradable polymers are rigid and lack the ideal elastic behavior for these applications. Biodegradable segmented poly(ester-urethane) (SPEU) offer a combination of mechanical properties and biocompatibility required for soft-tissue engineering applications. Electrospinning is a versatile technique to obtain tailor-made grafts with desirable size and thickness. In this work, we report the development of SPEU-based small-diameter vascular grafts by electrospinning. SPEU was synthesized in our laboratory from aliphatic diisocyanate, aliphatic polyester, and a novel aromatic chain extender. First, the solution intrinsic properties and processing parameters were studied in a traditional flat collector. Once an uniform non-beaded nanofibrous morphology was obtained, 5 mm internal-diameter tubes were made. The collector used consisted of a rotocollector with 5 mm-diameter mandrel with a grounded collector plate placed bellow. The membrane and tube morphology was observed by scanning electron microscopy (SEM). Micrographs were processed to obtain the mean diameter, diameter histogram, mean angle of alignment, and angle histogram. Thermal properties of raw and electrospun materials were also analyzed. The preparation of SPEU grafts is a crucial step towards the development of compliant vascular grafts. Since SPEU presents an elastic response similar to the one of elastin, it could be used as the main component in the media layer of a synthetic vascular graft.