In vivo response to an implanted shape memory polyurethane foam in a porcine aneurysm model

Abstract

Cerebral aneurysms treated by traditional endovascular methods using platinum coils have a tendency to be unstable, either due to chronic inflammation, compaction of coils, or growth of the aneurysm. We propose to use alternate filling methods for the treatment of intracranial aneurysms using polyurethane based shape memory polymer (SMP) foams. SMP polyurethane foams were surgically implanted in a porcine aneurysm model to determine biocompatibility, localized thrombogenicity, and their ability to serve as a stable filler material within an aneurysm. The degree of healing was evaluated via gross observation, histopathology and low vacuum scanning electron microscopy (LV-SEM) imaging after zero, thirty and ninety days. Clotting was initiated within the SMP foam at time zero (less than one hour exposure to blood prior to euthanization), partial healing was observed at thirty days, and almost complete healing had occurred at ninety days in vivo, with minimal inflammatory response.

Shape memory polyurethanes with oxidation-induced degradation: In vivo and in vitro correlations for endovascular material applications

“…Previous work by Rodriguez et al with these materials (HH60 composition) included the implantation and histopathological evaluation after 0, 30, and 90 days in porcine aneurysms [38]. The SMPs were incubated in enzyme baths of pancreatin, collagenase and trypsin (initially tested with control SMPs to determine no degradation would occur to the polymer, only to the tissue) in order to remove tissue using a modified version of Zhang’s tissue removal protocol [39].…”

Particulate Release From Nanoparticle-Loaded Shape Memory Polymer Foams

“…Additionally, their unique shape memory properties enable their catheter delivery through tortuous vasculature to the desired treatment site, where they expand to fill the site and promote clotting. Overall, these results combined with the positive prior in vivo study results indicate that the SMP foams present minimal risks from particulate release that may result in unintended downstream emboli formation and have high potential for use as effective and safe embolization devices [4,5,16,28].…”

“…However, due to an increase in the use of sophisticated imaging technology, prerupture aneurysm detection rates are rising [3]. Porous, low density shape memory polymer (SMP) foam is reported to be an effective aneurysm occlusion material with excellent biocompatibility as seen in a porcine model wherein rapid, stable thrombus formation and high volume occlusion was observed [4,5]. SMP foams are materials capable of maintaining a temporary shape and, upon application of a thermal, chemical, or optical stimulus, recovering their primary shape [6].…”

Mechanical and in vitro evaluation of an experimental canine patent ductus arteriosus occlusion device

“…Singhal et al (2012) have demonstrated ultra-low density SMP foams with up to 70× volume expansion, 97–98% shape recovery after multiple cycles, and sharp, tailorable transition temperatures between 45–70 °C. In addition, the foams have shown excellent biocompatibility in vitro and in vivo , exhibiting the recruitment of collagen and connective tissue to form stable scar tissue, as well as clot formation within two minutes (Rodriguez et al, 2014a, 2014b, 2012; Singhal et al, 2012). …”