Selective laser sintered bio-inspired silicon-wollastonite scaffolds for bone tissue engineering

The scaffolds, which morphologically and physiologically mimic natural features of the bone, are of high demand for regenerative medicine. To address this challenge, we have developed innovative bioactive porous silicon- wollastonite substrates for bone tissue engineering. Additive manufacturing through selective laser melting approach has been exploited to fabricate scaffolds of different architecture. Unique material combining osteoinductivity, osteoconductivity and bioactive elements allows flexibility in design. As the porous structure is required for the ingrowth of the bone tissue, the CAD designed scaffolds with pore size of 400 mu m and hierarchical gradient of pore size from 50 mu m to 350 mu m have been 3D printed and tested in vitro. The scaffolds have demonstrated not only the enhanced viability and differential patterning of human mesenchymal cells (hMSC) guided by the biomimetic design onto extra and intra scaffold space but also promoted the osteogenic differentiation in vitro. Both homogeneous and gradient scaffolds have shown the differential expression of primary transcription factors (RUNX2, OSX), anti-inflammatory factors and cytokines, which are important for the regulation of ossification. The effective elastic modulus and compressive strength of scaffolds have been calculated as 1.1 +/- 0.9 GPa and 37 +/- 13.5 MPa with progressive failure for homogeneous structured scaffold; and 1.8 +/- 0.9 GPa and 71 +/- 9.5 MPa for gradient-structured scaffold with saw-tooth fracture mode and sudden incognito failure zones. The finite element analysis reveals more bulk stress onto the gradient scaffolds when compared to the homogeneous counterpart. The findings demonstrate that as-produced composite ceramic scaffolds can pave the way for treating specific orthopaedic defects by tailoring the design through additive manufacturing.