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

Abstract

The synthesis of thermoset shape memory polymer (SMP) polyurethanes from symmetric, aliphatic alcohols and diisocyanates has previously demonstrated excellent biocompatibility in short term in vitro and in vivo studies, although long term stability has not been investigated. Here we demonstrate that while rapid oxidation occurs in these thermoset SMPs, facilitated by the incorporation of multi-functional, branching amino groups, byproduct analysis does not indicate toxicological concern for these materials. Through complex multi-step chemical reactions, chain scission begins from the amines in the monomeric repeat units, and results, ultimately, in the formation of carboxylic acids, secondary and primary amines; the degradation rate and product concentrations were confirmed using liquid chromatography mass spectrometry, in model compound studies, yielding a previously unexamined degradation mechanism for these biomaterials. The rate of degradation is dependent on the hydrogen peroxide concentration, and comparison of explanted samples reveals a much slower rate in vivo compared to the widely accepted literature in vitro real-time equivalent of 3% H2O2. Cytotoxicity studies of the material surface, and examination of the degradation product accumulations, indicate that degradation has negligible impact on cytotoxicity of these materials.

Biodegradable shape memory polymer foams with appropriate thermal properties for hemostatic applications

“…It is noteworthy that G25 had the slowest degradation rate, which is due to the oxidatively stable structure of Gly. Previous research has demonstrated that in oxidative conditions, the tertiary amines in TEA and HPED are oxidized to amine oxide to form primary amines, carboxylic acids, and aldehydes (Weems, Wacker, Carrow, Boyle, & Maitland, ). This research explains why the control TEA‐based foams (T30, T40, and T60), which contain higher percentage of tertiary amines, are more susceptible to oxidation than the Gly‐based foam (G25).…”

“…More significant differences were observed between the ester‐containing foams and their controls over time in oxidative degradation conditions. Previously, our group analyzed degraded SMP foams and their degradation products and proposed an oxidative degradation mechanism for HPED and TEA; the tertiary amine oxidizes into amine‐oxide, which further undergoes C–N fragmentation leading to the formation of carboxylic acids and aldehydes (Weems et al, ). All TEA‐based foams showed carbonyl peak shifts from 1,689 cm −1 to 1,696 cm −1 (Figure b) which are attributed to the fragmentation of C‐N bond from the tertiary amine of TEA or HPED to form carboxylic acid or aldehyde conjugates.…”

“…It is important to correlate the in vitro data to the in vivo time‐frame. Weems et al compared in vitro degradation data of porous SMP foams with in vivo data of foams implanted in porcine sidewall aneurysm (Weems et al, ). These results showed that 45 ± 3 days in 3% H 2 O 2 is comparable to 90 days in vivo and that 15 days in 20% H 2 O 2 is equivalent to 108 days in 3% H 2 O 2 .…”

Multifunctional Shape‐Memory Polymer Foams with Bio‐inspired Antimicrobials

“…An additional benefit to phenolic acids is their antioxidant properties; phenolic acids contain hydrogen donating groups that scavenge free radicals and reduce oxidation . Recently, we found that SMP foams are susceptible to oxidative degradation . Thus, in future work, we will obtain oxidative degradation profiles of phenolic acid‐containing SMP foams in addition to expanding the library of phenolic acids utilized in SMP foaming to further characterize their tunability.…”

Glycerin‐Based Polyurethane Obtained by Inverse Emulsion: Comparison Between Magnetic Induction and Conventional Heating

“…They can present different behaviors depending on their synthetic conditions and have considerable permeability, mainly since it can be controlled according to the ratio of their hydrophobic and hydrophilic chain moieties . Some of these PUs are highly researched because of their ability to biodegrade …”