Micro‐porous composite scaffolds of photo‐crosslinked poly(trimethylene carbonate) and nano‐hydroxyapatite prepared by low‐temperature extrusion‐based additive manufacturing

Abstract

Complex bony defects such as those of the orbital floor are challenging to repair. Additive manufacturing techniques open up possibilities for the fabrication of implants with a designed macro‐porosity for the reconstruction of such defects. Apart from a designed macro‐porosity for tissue ingrowth, a micro‐porosity in the implant struts will be beneficial for nutrient diffusion, protein adsorption and drug loading and release. In this work, we report on a low‐temperature extrusion‐based additive manufacturing method for the preparation of composite photo‐crosslinked structures of poly(trimethylene carbonate) with bone‐forming nano‐hydroxyapatite and noricaritin (derived from bone growth stimulating icariin). In this method, we extrude a dispersion of nano‐hydroxyapatite and noricaritin particles in a solution of photo‐crosslinkable poly(trimethylene carbonate) in ethylene carbonate into defined three‐dimensional structures. The ethylene carbonate is subsequently crystallized and extracted after photo‐crosslinking. We show that this results in designed macro‐porous structures with micro‐pores in the struts. The dispersion used to fabricate these structures shows favorable properties for extrusion‐based processing, such as a sharp crystallization response and shear thinning. The formed photo‐crosslinked materials have a micro‐porosity of up to 48%, and the E modulus, ultimate tensile strength and toughness are in excess of 24 MPa, 2.0 N/mm2 and 113 N/mm2 respectively. A sustained release of noricaritin from these materials was also achieved. The results show that the technique described here is promising for the fabrication of micro‐porous photo‐crosslinked composite structures of poly(trimethylene carbonate) with nano‐hydroxyapatite and that these may be applied in the reconstruction of orbital floor defects. Copyright © 2016 John Wiley & Sons, Ltd.