Investigation On Multilayered Shape Memory Vascular Scaffold With A Changeable Micropatterned Surface

Small diameter vascular grafts(Diameter<6 mm)are increasingly needed for clinical surgical intervention.Autologous grafts such as the saphenous veins and artificial Dacron(polyethylene terephthalate)or ePTFE(expanded polytetrafluoroethylene)grafts can be beneficial,but these substitutes may be unavailable due to insufficient source,morbidity and deficient long-term performance.Here,we developed a new 3D multilayered shape memory vascular scaffold with a hierarchically changeable micropatterned surface for vascularization,which employed typical shape memory 6a PEG-PCL(6 arm poly(ethylene glycol)-poly(?-caprolactone))as substrate.Square and rectangle were employed to regulate EC(endothelial cell)and VSMC(vascular smooth muscle cell),respectively.Firstly,the micropatterns were printed on c-6a PEG-PCL(crosslinked-6 arm Poly(ethylene glycol)-Poly(s-caprolactone))membrane by hot pressing technology.The c-6a PEG-PCL membranes,which had a square pattern on the inner layer and rectangular pattern on the outer layer,were rolled up to form vascular grafts.The graft possesses both excellent mechanical property,degradability and shape memory effect,with a suitable ransformation temperature at 37 ?.An in vitro simulation was conducted to confirm the feasibility of minimally invasive implantation,and the shape recovery of graft could support the blood vessel.Then,the EC and VSMC were seeded on the two patterns.The square pattern can promote EC proliferation,adhesion,migration,as well as expression laminin,while rectangular micropatterned surfaces can induce a circumferential alignment of VSMC and promote expression a-SMA(a-smooth muscle actin).Besides,our material and surface topographies are inert with respect to platelets.Finally,the angiogenesis of shape memory micropatterned grafts was tested.The grafts retained good patency and showed uniform blood flow profiles by Doppler,which confirmed the shape memory recovery.Square can promote EC adhesion and migration,resulting in rapid endothelialization,and circumferential arrangement of VSMC were detected in outer rectangular layers.There were a large of pro-healing M2 macrophages in the grafts,which is beneficial for revascularization.Also,the grafts were gradually degraded in vivo.A neonatal vascular tissue was regenerated after 120 days implantation,and the construction of neonatal vascular was similar to that of natural carotid arteries.