Design, Fabrication, and Characterization of a Shape Memory Polymer Embolic Device

Shape memory polymers (SMPs) are a unique class of smart materials that can remember two shapes, and can be remotely actuated to achieve a predefined shape by application of thermal energy. Porous scaffold of SMP foams enable high volume change up to 70 times. Use of these SMP foams in a minimally invasive treatment of cerebral aneurysms is of significant interest in the biomedical community. In the application of treating aneurysms, a spheroid SMP foam is envisioned to be compressed to a rod-like cylindrical secondary shape. The device in this secondary shape can then be delivered through a catheter to the aneurysm site and, once in the aneurysm, can be actuated to recover the primary shape to fill the aneurysmal protuberance. Blood is expected to infiltrate and clot within the porous internal structure of the expanded SMP foam, ultimately leading to complete isolation of the aneurysm from the parent artery through tissue healing. This study reports the functional characterization of SMP foam with respect to the design and the fabrication of the prototype embolic device for treatment of cerebral aneurysms. The pressure exerted by the expanding SMP foam on the aneurysms wall during the occlusion is estimated. Frictional loads between SMP foam and a catheter pathway are investigated. This is a critical factor in the feasibility of transcatheter delivery of a SMP foam device. Porcine in vitro and in vivo aneurysm models are used to test and validate the deployment process of the proposed device. Important aspects are studied and discussed, such as deliverability through a catheter, recovery of the primary shape by thermal actuation, and fluoroscopic visualization of the device during the delivery. Finally, the performance of SMP embolic device, which is the endovascular delivery and the occlusion of porcine aneurysms, are compared to performance of Guglielmi Detachable Coil that is considered as the standard treatment. 90 and 180 days follow-up studies present promising healing responses of the SMP treated aneurysm. This study forms an important step towards the realization of these devices in clinical practice