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Conventional endovascular embolization of intracranial (or brain) aneurysms using helical detachable platinum coils can be time-consuming and occasionally requires retreatment due to incomplete coil packing. These shortcomings create a need for new biomedical devices and methods of achieving brain aneurysm occlusion. This paper presents a biocompatible and highly porous shape memory polymer (SMP) material with potential applications in the development of novel endovascular devices for treating complex intracranial aneurysms. The novel highly porous polyurethane SMP is synthesized as an open cell foam material with a glass transition temperature (Tg) of 39 °C using a sugar particle leaching method. Once heated above the Tg, the compressed SMP foam is able to quickly return to its original shape. An electrical resistance heating method is also employed to demonstrate a potential triggering design for the shape recovery process in future medical applications. The mechanical properties of the developed SMP foam are characterized at temperatures up to 10 °C above the respective Tg. The results from this work demonstrate that the porous SMP material developed in this study and the electrical resistance heating trigger mechanism provide a solid foundation for future design of biomedical devices to enhance the long-term therapeutic outcomes of endovascular intracranial aneurysm treatments.

Current endovascular therapies for intracranial aneurysms face limitations that include aneurysm recurrence and incomplete occlusion. These challenges can potentially be addressed by occluding the aneurysm space with shape memory polymers (SMPs) that are tailorable to patient‐specific aneurysm geometries to improve the suboptimal treatment outcomes associated with coil embolization. However, deployment of the SMP‐based device into the aneurysm requires external stimuli to trigger shape recovery. Thus, herein, the infiltration of carbon nanotubes (CNTs) in a polyurethane SMP foam is investigated, and Joule‐heating triggering for SMP shape recovery in endovascular therapy applications is demonstrated. The results show that CNTs can be successfully infiltrated in the SMP foam, providing tunable resistivity and shape recovery time, and that CNT infiltration reduces the glass transition temperature of the SMP and alters its mechanical properties, which is evidenced with a cumulative stress reduction in cyclic compression tests. Finally, the Joule‐heating capability of the SMP material is examined using a proof‐of‐concept in vitro occlusion experiment of an idealized saccular aneurysm model. Collectively, this study indicates that CNT infiltration of SMP foams is a promising approach in the design of electrically triggered embolic devices for individualized treatment of intracranial aneurysms.

This paper presents a novel medical device developed using shape memory polymer (SMP) foams for the endovascular treatment of intracranial aneurysms (ICAs). The SMP foam is fabricated, characterized, and experimentally investigated to better understand their potential for endovascular embolization of ICAs. Polyurethane-based SMP is successfully synthesized and characterized. The SMP foam is manufactured using cast molding, and characterized using an electro-thermal triggering mechanism to fully understand their shape recovery capability. The successful completion of this work will serve as a solid foundation for the development of new biomedical devices to treat intracranial aneurysms and develop an optimal releasing procedure for future animal study.

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Fibers and fabrics are often used to reinforce shape memory polymers (SMPs) to improve their mechanical strength and properties, and the composites have been widely used in engineering. However incorporation of fibers and fabrics in SMPs are often accompanied with the degradation of thermal mechanical properties and shape memory effect. The thermomechanical properties and degradation mechanisms of a shape-memory polymer composite (SMPC) were investigated. Up to 100% extension, the SMPCs showed good shape memory effect with excellent recovery ratio, recovery stress and mechanical properties; while beyond that the recovery ratio and stress of the composites deteriorate rapidly due to the significant delamination and debonding of fibers and fabrics from the SMP resin and accumulation of broken fibers.

Intracranial aneurysms have the potential to be fatal; when detected, they must be treated promptly by surgical clipping or by endovascular methods. The latter, while having better long-term overall survival than the former, fail to provide complete occlusion of the aneurysm lumen, creating risks for therapy-related adverse events, such as embolic device migration or recanalization. Polyurethane shape memory polymers (SMPs) have the potential to provide patient-specific treatment to reduce rates of incomplete occlusion and mass effect. In this study, SMP matrices are infiltrated with carbon nanotubes (CNTs) to induce electrical conductivity and provide a precise triggering method for deployment of the embolic device. Through thermomechanical characterization of the composite, it was determined that CNTs play a significant role in resistivity of the SMP foam and its ultimate shape recovery properties. Cyclic mechanical testing allowed to determine that CNTs might induce polymeric matrix damage, creating the need for new approaches to CNT infiltration. The studied composite foams were able to occlude an in vitro idealized aneurysm phantom model, which allowed to conclude that the proposed CNT-infiltrated SMP foams exhibit potential as biomedical devices for endovascular therapy of intracranial aneurysms.

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