Effects of Carbon Nanotube Infiltration on a Shape Memory Polymer‐Based Device for Brain Aneurysm Therapeutics: Design and Characterization of a Joule‐Heating Triggering Mechanism

Abstract

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.

Shape Memory Polymer-Based Endovascular Devices: Design Criteria and Future Perspective

“…SMP/CNT foams emit heat when the direct current is applied, allowing the recovery of the compressed foam (Figure 6). However, we also observed that CNT infiltration reduced T g of the material and deteriorated its capacity to withstand cyclic deformation [58]. Other researchers have also found similar behaviors for CNT-infiltrated SMP composites [85,86].…”

“…Currently, SMP-based endovascular devices are under development so that they can be utilized in a similar manner. SMP design for endovascular devices can follow two major approaches: (i) SMP-coated coils such as Trellix [19,46]; and (ii) coil-free SMPs foams [55][56][57][58]. SMP-coated coils have a similar goal to the hydrogel coils: increasing the packing density may augment the volume of the coil.…”

“…This method provides the high tunability of the cell/pore shape and size, which depend on the choice of particles. Common leaching agents that have been used in the literature include sodium chloride [67,68], sugar [56,58], and gelatin [69], among others. In our group, we leached polyurethane SMPs using sugar particles and demonstrated its use to obtain highly compressible SMP foams with pore geometries that mimic the sugar crystal morphology [56,58].…”

“…In our group, we developed conductive SMPs via CNT infiltration in sugar-leached polyurethane foams [56,58]. We demonstrated that CNTs are an effective and facile method for the shape recovery of the porous SMP foams.…”

A protocol for the reduction of applied torque on parent vessel during elastase-induced aneurysm formation using rabbit animal models

“…[35] Our findings in this modified protocol will be applied to the development of a novel coil-free endovascular device. We have developed a shape memory polymer (SMP) for endovascular embolization of patient-specific aneurysm geometries, [36][37][38][39] and we believe that this elastase-induced aneurysm formation protocol can aid in the translation of our material to the pre-clinical setting. We plan to test our material with a statistically powerful sample size, to determine the pre-clinical safety and effectiveness of our SMP device (measured using RROC scale, Fig.…”