Fabrication and Surface Modification of PLLA Films for Cardiovascular Applications

Book excerpt: Cardiovascular diseases have emerged as a major concern since they are the first cause of death in developed countries. The advent of percutaneous trans luminal coronary angioplasty consisted in an alternative to invasive surgery. Especially the introduction of cardiovascular stents has significantly meliorated the potential of angioplasty, e.g. with the use of drug eluting and bio absorbable stents. Still, restenosis remains a major implant-related complication and can imply re intervention. Therefore, research has focused on limiting and/or avoiding restenosis by investigating the field of fully biodegradable stents. The main aspect of this project is to focus on the fabrication of PLLA films to then characterise them chemically, physically and mechanically to be able to use this material in the future as a totally biodegradable cardiovascular stent. The first step was to choose which film fabrication process to use in order to obtain the best aspect and properties for our application. Then enhance the process by focusing on ameliorating properties and surface aspect of the film. The following step was to create carboxyl groups as a preliminary step for bio functionalization. This was done by different surface treatment: oxygen plasma, ozone and sodium hydroxide. And finally we compared the degradation of selected films with a fully bio absorbable stent made of the same polymer. Optimal film fabrication was obtained with solvent casting using chloroform as solvent with 2,5g of PLLA PL65 and 70ml of chloroform. To improve properties and surface aspect, thermal treatment were carried out pre and post fabrication. Films had less bubbles but were less transparent and more rigid due to higher cristallinity. Mechanical properties increased (Young modulus and tensile strength) and residual chloroform evaporated totally making films non cytotoxic. Optimal surface treatment was obtained with plasma.