Characterization of Biopolymeric Micro- Nano Structured 3D Porous Matrices in Combination with Bone Marrow Derived Mesenchymal Stem Cells for Bone Regeneration

Approximately half a million individuals suffer from fractures every year and the demand for bone graft procedures is on a continuous increase. Scaffold based bone tissue engineering (BTE) has made great progress in regenerating lost bone tissue. Several materials are used for fabrication of scaffolds for BTE. Biopolymers apart from being a cost effective alternative to conventional synthetic polymers used for fabrication of scaffolds, offer advantages such as greater bioactivity and biocompatibility with mammalian tissue. A clinically relevant cell type proven to improve bone healing is bone marrow derived mesenchymal stem cells (MSCs). The biomaterial used to deliver these stem cells can induce their differentiation into the osteoblastic lineage and hasten bone healing. In this project we used polysaccharide and protein chemistry in a hierarchical scaffold design to accomplish structural stability and bioactivity. In these scaffolds, a cellulose derivative formed the micro scale structures, while collagen the most abundant osteogenic extracellular matrix (ECM) protein of bone, formed the self assembled nanostructures. This dissertation aims at characterizing these three- dimensional (3D) porous biopolymeric scaffolds of cellulose acetate (CA) and cellulose acetate coated with Nano-fibrous collagen (CAc), in terms of their ability to induce bone healing in combination with MSCs. The CA and CAc scaffolds were compared to similar polyester (Poly-lactic acid co-glycolic acid) (PLGA) 3D porous scaffolds for their material properties and biological performance. It was seen that the CA scaffolds had greater hydrophilicity and when functionalized with collagen led to a more biomimetic self-assembly of collagen nanofibers. During the induced differentiation of seeded human bone marrow derived mesenchymal stem cells (hMSCs) in vitro, the cells on polysaccharide scaffolds showed higher levels of osteoblastic progression than the cells on the polyester scaffolds. The polysaccharide scaffolds also showed greater biocompatibility at twelve weeks of subcutaneous implantation in rats. On the other hand, polyester scaffolds started exhibiting increased foreign body response (FBR) by later time points. Finally, when implanted into critical sized calvarial defects of mice, the polysaccharide scaffolds seeded with bone marrow stromal cells showed greater bone formation and greater levels of collagen content, along with a more even distribution of osteoblastic markers throughout the scaffold structure than the control polyester scaffolds. Hence these findings demonstrated the potential of cellulose acetate and collagen, micro- nano structured biopolymeric scaffolds to be used in combination with MSCs as a biomaterial for bone regeneration.