Design of bimodal PCL and PCL-HA nanocomposite scaffolds by two step depressurization during solid-state supercritical CO_2 foaming

摘要

This communication reports the design and fabrication of porous scaffolds of poly(?μ-caprolactone) (PCL) and PCL loaded with hydroxyapatite (HA) nanoparticles with bimodal pore size distributions by a two step depressurization solid-state supercritical CO_2 (scCO_2) foaming process. Results show that the pore structure features of the scaffolds are strongly affected by the thermal history of the starting polymeric materials and by the depressurization profile. In particular, PCL and PCL-HA nanocomposite scaffolds with bimodal and uniform pore size distributions are fabricated by quenching molten samples in liquid N2, solubilizing the scCO_2 at 37 °C and 20 MPa, and further releasing the blowing agent in two steps: (1) from 20 to 10 MPa at a slow depressurization rate, and (2) from 10 MPa to the ambient pressure at a fast depressurization rate. The biocompatibility of the bimodal scaffolds is finally evaluated by the in vitro culture of human mesenchymal stem cells (MSCs), in order to assess their potential for tissue engineering applications. The successful fabrication of bimodal porous scaffolds made of polycaprolactone (PCL) and PCL loaded with hydroxyapatite nanoparticles via the two step depressurization of solid-state supercritical CO_2 foaming is reported. The entire process was performed at 37°C, so opening new routes to the design of porous bioactive scaffolds for tissue engineering.