Free Radical Scavenging Biomaterial
While encapsulation of cells within perm-selective polymers has resulted in the dramatic reduction of immune cell activation and subsequent transplant destruction, it fails to prevent inflammation and indirect immune activation, which commonly results in oxidative stress. Increases in free radicals at the site of transplant represent a particular challenge for islets, as they are markedly low in antioxidant enzyme activity relative to other tissues. Supplementation of islet grafts with antioxidants may provide protection from free radical-induced apoptosis. Recently, cerium oxide nanoparticles, or nanoceria, have demonstrated behavior that mimics free-radical scavenging enzymes. Ubiquitous and self-renewing in their free radical scavenging capabilities, nanoceria also benefits from multiple catalytic sites in its nanoparticle form. Limited research is available on the effects of systemic exposure to free metal-oxide nanoparticles, therefore localization of nanoparticle dose to the transplant site is essential. Furthermore, localization of particles to the site of transplant may enhance their effect. In our laboratory, we are developing methods for the localization of nanoceria to the implant site by integrating these particles within the encapsulating hydrogel. We have found the resulting hydrogels to retain their ability to scavenge free radicals and protect the embedded cells from free radical damage. We are currently exploring the potential of these materials to mitigate damage following transplantation.