Patterned polymeric scaffolds for cardiovascular applications

Coronary artery disease (CAD) is the principal cause of death in the world. It is the result of plaque accumulation which narrows and blocks artery’s lumen. As a solution, percutaneous intervention is a revolutionary technique which introduces a catheter that delivers a balloon at the site of the vessel narrowing. Tubular cardiovascular scaffolds, called stents, are integrated in percutaneous intervention as a support to give the mechanical strength needed to stenotic arteries to allow the blood flow. Generally, these stents are inert and remain into de body of the patient forever. New generation stents are bioresorbable stents (BRSs) that create a temporary mechanical support to prevent restenosis and vascular recoil. These BRSs would ideally disappear once its main function has been served. In this work, we have fabricated polymeric BRSs by 3D printing. To that end, two different polymers were used for obtaining two different conditions of stents: high molecular PLLA and a PLLAPCL copolymer. Stents manufacture was carried out by 3D printing through solvent-cast direct-writing (SC-DW) and it has been developed a new 3D printer accessory in order to decrease evaporation rate of the ink while printing. Additionally, patterned BRSs were produced when printed onto micropatterned rotating mandrel in order to obtain an increased endothelial cell adhesion. Two other concerns of biodegradable materials for stents are presented: the control of degradation rate and the effects of sterilization on physical-chemical and mechanical properties. Therefore, the current project presents an accelerated degradation assay in alkaline medium over 10 days of degradation, which showed an effective and fast way to study hydrolysis erosion of stents. The evaluation of the degradation assay was in the following aspects: changes of morphology, thermal properties and changes in crystallinity, as well as mechanical properties. Furthermore, BRSs were sterilized through two different methods: gamma radiation and ethylene oxide. After the sterilization process, characterization analysis was performed in order to evaluate their thermal and crystallinity properties, molecular weight changes as well as mechanical properties. The results of the project are: (1) a new method to improve manufacturing efficiency of stents through 3D printing; (2) the design of a fast and effective accelerated degradation assay and; (3) the selection of the proper sterilization method in order to avoid damage on biodegradable stents properties