Cellulose based micro- nano structured scaffolds for bone regeneration

Abstract

Event Abstract Back to Event Cellulose based micro- nano structured scaffolds for bone regeneration Aja Aravamudhan1, 2 and Sangamesh G. Kumbar1, 2, 3, 4 1 University of Connecticut Health Center, Institute for Regenerative Engineering, United States 2 University of Connecticut Health Center, Department of Orthopeadic Surgery, United States 3 University of Connecticut Health Center, Department of Materials Science and Engineering, United States 4 University of Connecticut Health Center, Department of Biomedical Engineering, United States Introduction: Several polymer based scaffold systems have been used as an alternative to traditional autografts and allografts to repair non-healing defects of the bone. These materials fail to provide required osteoconductive, osteoinductive, and osteointegrative properties in line with autografts. Natural polymers have the advantage of being similar to biological macromolecules and elicit favorable tissue healing responses, in contrast to synthetic polymers that are used conventionally in scaffolds for bone regeneration. In this study, we present the characterization of cellulose acetate based scaffolds in comparison to synthetic poly(lactic-co-glycolic acid) (PLGA) scaffolds with respect to their ability to promote hMSC’s progression into osteoblastic lineage in vitro, biocompatibility in a rat subcutaneous implantation model and bone healing capability in a mouse calvarial defect model. Materials and Methods: Cellulose acetate (CA) (Sigma-Aldrich, 30kD) and (PLGA) (P) microparticles were prepared using emulsion solvent evaporation method. Solvent sintering technique[1],[2] was employed to prepare CA scaffolds and heat sintering was used for PLGA. Composite scaffolds of CA (CAc) PLAGA (Pc) were prepared by coating 0.1 % collagen solution on the scaffolds. In-vitro studies, using hMSCs in basal media (BM) and osteogenic media (OM), were conducted by seeding 500,000 cells per tablet type scaffold. Osteoblastic differentiation was monitored by alkaline phosphate activity assay and mineralization along with change in osteogenic gene expression (RUNX2, Col1, Col3, and BSP after 21 days). Further, CA, CAc and PLGA scaffolds were implanted subcutaneously in rats to determine the biocompatibility of the materials by contrasting the immune responses between the groups using histological staining. The scaffolds seeded with bone marrow stomal cells from donor mice (Col 3.6 cyan+) were implanted in critical sized (3.5mm dia) calvarial defect in mice (Col 3.6 GFP+) and its ability to heal bone was evaluated by histological staining. Results and Discussion: Osteogenic genes such as RUNX2, collagen1 and BSP showed greater expression on the CA and CAc groups in contrast to the PLGA groups (Figure 1.a.). The CA and CAc scaffolds showed greater progression of osteogenic phenotype as seen by greater protein levels of Col1 and BSP (Figure 1.b.) and mineralization of osteoinduced hMSCs on these scaffolds (Figure 1.c.). Among the scaffolds implanted subcutaneously (Figure 2.a.), the foreign body response (FBR) reduced significantly over time on the CA groups, while the FBR response increased over time on PLGA (Figure 2.b.). These results indicate the long-term biocompatibility of CA groups over synthetic PLGA. Finally, CA scaffolds seeded with MSCs showed uniform bone formation in contrast to PLGA scaffolds that had islands of new bone formation (Figure 2.c.). The greater hydrophilic and biomimetic nature of CA may be attributed to these differences. Conclusions: The CA and CAc scaffolds induced and maintained osteoblastic differentiation of the seeded hMSCs. The biocompatibility and cellularity of CA increased over time, while that of PLGA decreased over time. The stable and more hydrophilic properties of CA could be attributed to these results. Finally the bone formation by CA scaffolds was uniformly well distributed through the scaffold than PLGA, reflecting the superior osteogenic performace of the polysaccharide-based scaffolds. Hence CA based polysaccharide platform may be a viable alternative to synthetic polymers like PLGA in bone tissue engineering. Coulter Foundation, National Science Foundation (IIP-1355327, IIP- 1311907 and EFRI-1332329); Raymond and Beverly Sackler Center