Influence of the Contrast Agent on the Properties of Chitosan Thermogel: Towards a New Embolic Agent for Aneurysms [English translation]

Endovascular aneurysm repair (EVAR) is a minimally invasive alternative to open surgical repair developed to treat high risk patients suffering from abdominal aortic aneurysm (AAA). The goal of the procedure is to exclude the aneurismal sac from blood circulation by deploying a covered stent called stent-graft. The major limitation of this technic is the occurrence of frequent complications, in particular persistence of blood perfusion in the aneurysm, called endoleaks. Embolizing agents have been developed to occlude flow and prevent endoleaks, but their effectiveness is limited. In this work we propose to create a novel embolizing agent based on chitosan thermogels. Since chitosan is not radiopaque, a contrast agent (AdC) needed to be added to the base solution to allow good control and follow-up of the embolisation. The aims of this research were to determine the influence of the three generations of AdC on the chitosan solution and confirm the feasibility to use it for the embolisation of AAA. To reach these objectives, the viscoelastic properties and gelation kinetic of the solutions and the mechanical properties, the cytotoxic potential and the release rate of the AdC of the gels were evaluated. Formulations made of 20% v/v of AdC obtained good results for their use like embolic agents compared with products presently used. Their viscosity and kinetic of gelation were sufficiently high to avoid migration of the solution in the peripheral system and the pharmacokinetic of the AdC allowed a good temporary visualization while the gel has a low cytotoxic effect. This project confirms the feasibility of using a radiopaque thermogelling chitosan solution for the embolisation of AAA and permits a better understanding of the role of AdC on the thermogel properties.