Biomimetic Calcium Phosphate-Polycarbonate Composite Scaffolds for Bone Tissue Engineering

Shuang S Chen and Joachim Kohn New Jersey Center for Biomaterials, Rutgers The State University of New Jersey, Piscataway, New Jersey 08854, United States. Statement of Purpose: Large bone defects resulting from trauma, tumor resection, congenital abnormalities or reconstructive surgery are challenging clinical problems that are usually treated with autografts and allografts. However, donor site morbidity and limited supply of autograft and the limited bioactivity of allograft have stimulated the development of bone graft substitutes [1]. Initial results with bone regeneration scaffolds composed of tyrosine-derived polycarbonates such as E1001(1k) (Fig 1) have been promising, due to their desirable osteoconductivity, and excellent in vivo bone biocompatibility [2]. To further enhance the performance of these scaffolds in vivo, we developed a process that deposits a coating of calcium phosphate within the pores of the scaffold and confirmed a significant improvement of the in vivo performance of the coated scaffolds [3]. In this study, we further optimized the coating process and were able to define the type of calcium mineral (either hydroxyapatite (HA) or dicalcium phosphate dihydrate (DCPD)) formed within the pores of the E1001(1k) scaffolds. We studied in vitro cell viability, attachment, proliferation and osteogenic differentiation of human mesenchymal stem cells (hMSC). . Methods: 3D porous scaffolds were fabricated from E1001(1k) (Fig. 1) using a combination of porogen leaching and freezing drying [2]. The polymeric scaffolds were coated with calcium phosphate using a modified alternate soaking method in basic and acidic phosphoric solution. Scaffold pore size and morphology were investigated using Scanning Electron Microscopy (SEM). The identity of calcium phosphates was determined by X-ray diffraction (XRD). The in vitro calcium phosphate dissolution and scaffold degradation were studied by incubating scaffolds in PBS at 37°C up to 28 days. The in vitro cell viability, attachment, proliferation and osteogenic differentiation on E1001(1k), E1001(1k)+HA, and E1001(1k)+DCPD scaffolds were investigated using hMSC.