Mechanical and in vitro evaluations of composite PLDLLA/TCP scaffolds for bone engineering

Bone tissue engineering scaffolds have two challenging functional tasks to play; to be bioactive by encouraging cell proliferation and differentiation, and to provide suitable mechanical stability upon implantation. Composites of biopolymers and bioceramics unite the advantages of both materials, resulting in better processability, enhanced mechanical properties through matrix reinforcement and osteoinductivity. Novel composite blends of poly(L-lactide-co-D,L-lactide)/tricalcium phosphate (PLDLLA/TCP) were fabricated into scaffolds by an extrusion deposition technique customised from standard rapid prototyping technology. PLDLLA/TCP composite material blends of various compositions were prepared and analysed for their mechanical properties. PLDLLA/TCP (10%) was optimised and fabricated into scaffolds. Compressive mechanical properties for the composite scaffolds were measured. In vitro studies were conducted using porcine bone-marrow stromal cells (BMSCs). Cell-scaffold constructs were induced using osteogenic induction factors for up to 8 weeks. Cell proliferation, viability and differentiation capabilities were assayed using phase-contrast light microscopy, scanning electron microscopy, DNA quantification (Pico Green), Alamar Blue metabolic assay; FDA/PI fluorescent assay and western blot analysis for osteopontin. Microscopy observations showed BMSCs possessed high proliferative capabilities and demonstrated bridging across the pores of the scaffolds. FDA/PI staining as well as Alamar Blue assay showed high viability of BMSCs cultured on the composite scaffolds. Cell numbers, based on DNA quantitation, were observed to increase continuously up to the eighth week of study. Western blot analysis showed increased osteopontin synthesis on the scaffolds compared to tissue culture plastic. Based on our results the PLDLLA/TCP scaffolds exhibited good potential and biocompatibility for bone tissue engineering applications.