Increased X-ray Visualization of Shape Memory Polymer Foams by Chemical Incorporation of Iodine Motifs

Abstract

Shape memory polymers can be programmed into a secondary geometry and recovered to their primary geometry with the application of a controlled stimulus. Porous shape memory polymer foam scaffolds that respond to body temperature show particular promise for embolic medical applications. A limitation for the minimally invasive delivery of these materials is an inherent lack of X-ray contrast. In this work, a triiodobenzene containing a monomer was incorporated into a shape memory polymer foam material system to chemically impart X-ray visibility and increase material toughness. Composition and process changes enabled further control over material density and thermomechanical properties. The proposed material system demonstrates a wide range of tailorable functional properties for the design of embolic medical devices, including X-ray visibility, expansion rate, and porosity. Enhanced visualization of these materials can improve the acute performance of medical devices used to treat vascular malformations, and the material porosity provides a healing scaffold for durable occlusion.

Chemical Modifications of Porous Shape Memory Polymers for Enhanced X-ray and MRI Visibility

“…This work will build upon previous work by Nash et al who achieved adequate visualization of thermoset SMP foams by chemically incorporating iodine-containing motifs [ 19 ]. The radiopaque monomer used in this work is 5-amino-2,4,6-triiodoisphthalic acid (ATIPA) which contains a triiodobenzene ring with an amine group and two carboxylic acid groups for incorporation into the polyurethane network.…”

“…The foaming procedure was adapted from Nash et al to accommodate addition of gadolinium [ 19 ]. The hydroxyl components (0.6 molar eq.)…”

“…IMPEDE device (Shape Memory Medical, Santa Clara, CA, USA) containing a Pt coil and marker band was used as a positive control. Samples were also imaged through a ½” aluminum plate which served as a bone analog with respect to X-ray attenuation [ 19 ]. Images were converted to 8-bit grayscale, processed to remove the background, and analyzed using ImageJ to determine X-ray density.…”

“…The material used in this work is based on Nash et al, and is an amorphous thermoset SMP where the glass transition temperature (T g ) is controlled by tuning the material crosslink density [ 19 ]. The addition of GPA to this material system will increase T g due to increased polymer network rigidity and crosslinking.…”

Shape Memory Polymer Foams Synthesized Using Glycerol and Hexanetriol for Enhanced Degradation Resistance

“…The SMP foam system has been researched extensively by the Maitland group for use in biomedical devices. This material system is an amorphous, shape memory polymer with high porosity and ultra-low density [ 3 ], Additionally, physical and chemical properties of the material can be tuned depending on the final application [ 12 , 13 , 14 ]. Singhal et al modified the actuation rate of the SMP foam by altering its chemical structure.…”