NANOCOMPOSITE SCAFFOLDS FOR BONE TISSUE ENGINEERING

Abstract

Worldwide the number of bone damage/fracture, due to traumatic and accidental injuries, has been growing exponentially. Currently available treatments, for bone repairing, are slow, and often full functional recovery is not achieved. Hence, bone tissue engineering (BTE) has gained significant attention, where scaffold material plays an important role for repairing/regenerating bone-tissues. Scaffold, for BTE, has to be slowly-biodegradable, biocompatible, porous, mechanically strong, and should show cell proliferation and differentiation along with many other characteristics. One material cannot provide all these properties and that is why different materials are mixed to make a composite suitable for BTE. In this study I developed nanocomposite scaffolds consisting of alginate (A), gelatin (G), graphene oxide (GO), nanoceria (NC) and nanohydroxyapatite (nHAp), where alginate shows structural similarity to extra cellular matrix and easy crosslinking by Ca2+ ions; gelatin shows good cell adhesion; NC shows free radical scavenging; and GO and nHAp can induce mechanical strength, low-degradation and aid in differentiation of stem cells into bone cells. Freeze drying method, being very simple, was applied to fabricate the nanocomposite scaffolds. In the first study, gelatin-alginate-GO scaffold was fabricated. The incorporation of GO enhanced the compressive strength of the scaffolds significantly compared to the gelatin-alginate (GA) scaffold. In vitro studies, by seeding MG-63 cells over the nanocomposite scaffolds, revealed an enhancement in cell attachment and proliferation as compared to the GA scaffold: this indicates the positive effect of the GO on the scaffold properties. Cell differentiation studies with mesenchymal stem cells, seeded in the scaffolds, revealed higher expression of osteoblast transcription factors (RunX2 and Osteocalcin) and alkaline phosphatase activity―indicating the scaffold to be a good osteoinductive material. Next, nHAp/GO-GA scaffold has been explored for BTE. The resulting scaffold yields synergistic results in terms of mechanical strength, cell attachment, proliferation and differentiation. In third study, the problem, related to high oxidative stress due to free radical generation during bone healing, has been addressed by developing GA—NC scaffold; by incorporating NC in GA. Incorporation of NC has increased the mechanical properties. Additionally, GA—NCs depicts competent cell attachment, proliferation and viability. The results for osteogenic differentiation studies (i.e. ALP activity, RunX2 and osteocalcin expression) have indicated that GA—NCs scaffolds hold potential to assist differentiation of mesenchymal stem cells to osteoblast. Finally, the results for free radical scavenging functionality demonstrate that GA—NCs are capable of reducing free radicals.