3D printing of porous poly(ε-caprolactone)poly(trimethylene carbonate)-poly(ε-caprolactone) triblock copolymers and nano-apatite composite structures

Biodegradable porous poly(epsilon-caprolactone)-poly(trimethylene carbonate)-poly(epsilon-caprolactone) triblock copolymers (PCL-b-PTMC-b-PCL) were synthesized by sequent epsilon ial polymerization of trimethylene carbonate (TMC) and epsilon-caprolactone (CL), and novel composites of PCL-b-PTMC-b-PCL with different amounts of nano -apatite (nAp) were prepared. This PTMC-based polymer matrix, which does not degrade into acidic compounds, together with the nanometer-sized apatite, which influences cell behavior, is an ideal bone regenerative material. Solvent casting these composites from chloroform solutions yielded solid films with excellent handling properties. The E -modulus of the nano -composite materials increases with nAp content, while toughness, tensile strength and elongation at break decrease.Using EC as solvent, porous composite films of PCL-b-PTMC-b-PCL and nAp could readily be prepared. The composites in EC were processed into form -stable designed tissue engineering scaffolds by 3D printing at relatively mild conditions. Besides the pore network structure with pores of 530 to 620 mu m which corresponded to the design, smaller pores of 5-30 mu m (due to EC crystallization) and even smaller ones of 200-500 nm (resulting from liquid -liquid exchange upon extraction of the solvent in the polymer rich phase) were observed in the printed composite scaffolds.