Fabrication of a Free Radical Scavenging Nanocomposite Scaffold for Bone Tissue Regeneration

Abstract

Oxidative stresses have become a large influence on bone tissue regeneration. Increased by trauma and fracture, reactive oxygen species (ROS) negatively impact the remodeling function of osteoblasts by damaging DNA and cellular structures while triggering apoptosis. This greatly hinders the efficacy of bone grafts to facilitate bone remodeling. Cerium oxide nanoparticles (CNPs) have been utilized to reduce ROS and have made an impact in biological applications. In this study, we fabricated bioactive, nanocomposite scaffolds incorporating cerium oxide nanoparticles. The architectural, chemical, and mechanical properties of the scaffolds were characterized using techniques such as scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and compression testing. Biological assessments were completed to gauge the pro-osteogenic nature of the scaffolds through the attachment, viability, and mineralization of a pre-osteoblast cell line. Finally, free radical scavenging (FRS) function of the scaffolds was tested by measuring the decomposition of hydrogen peroxide over time and quantifying the cytotoxicity of cells on scaffolds after inducing oxidative stress. Through these assessments, it was determined that the nanocomposites contained the desired porous architectural and chemical properties. Scaffolds exhibited biocompatibility by supporting cell attachment, viability, and initiation of mineralization in the absence of supplemental mineralization-promoting factors. FRS behavior was displayed via a statistically significant reduction in scaffold-mediated hydrogen peroxide concentration and functional protection of cells from induced oxidative stress. In this work, we show that the successful incorporation of CNPs into nanocomposite scaffolds was able to decrease free radical damage to cells while providing a suitable environment for pre-osteoblast cells. The function of bone-forming cells, osteoblasts, in the bone remodeling cycle is hindered by oxidative stress created by an increase of reactive oxygen species. This is often seen at sites of injury and surgery, where bone grafts are often utilized. Our group investigated incorporating cerium oxide nanoparticles into a bioactive polymer-ceramic nanocomposite scaffolds for bone grafting applications. By incorporating the nanoparticles into our system, we are able to create a bioactive scaffold that can reduce reactive oxygen species and support osteogenic cell growth, both requirements for bone tissue formation. After initial in vitro testing, we would like to expand our investigation of the nanocomposite system in various in vivo models. To begin, an ectopic study in mice to determine biocompatibility, immune response, and mineralization. Additional studies would follow including critical size defect models in larger animal models.