Mesoporous Silica Nanoparticles to Tune Oxidative Degradation Rates in Composite Shape Memory Polymers

Abstract

Biomedical applications of shape memory polymers (SMPs) are limited by their biostability, degradability, and possible toxicity risks after implantation. Mesoporous silica nanoparticles (MSNs) were used to increase the oxidative biostability (increase time until degradation occurs) using antioxidants and to induce oxidative degradation through incorporation of hydrogen peroxide-containing MSNs with modified surfaces. The presented results confirm increased oxidative stability using antioxidants, and alternatively, oxidatively degraded SMPs when using MSNs and peroxide. Thermal stability was increased by approximately 10% with the inclusion of antioxidants. With the surface modification and incorporation of hydrogen peroxide, the elastic modulus was nearly 8 times greater, indicative of oxidative degradation and the strain to failure was decreased to 20% of that of the control formulation. In phosphate buffered saline (PBS), the SMPs were found to undergo mass loss until the solid polymer degraded completely, unlike the control formulations which have been found to be hydrolytically stable for more than a year with no change in mass.