Preparation and characterization of 3D composite scaffolds based on rapid-prototyped PCL/β-TCP struts and electrospun PCL coated with collagen and HA for bone regeneration

In general, bioceramics such as β-tricalcium phosphate (β-TCP) and hydroxyapatite (HA) are promising biomedical materials for bone tissue regeneration, because of their good osteoconductivity and, in some cases, osteoinductivity, whereas their shortcomings may include low mechanical fracture toughness and brittleness. One reinforcing technique is to use a coating process with various composite systems consisting of synthetic biopolymers and bioceramics. However, the coating ability can be limited, because of the hydrophobic nature of synthetic polymers, such that the coating solution can sporadically clog or block the designed pore structure, and in some cases, a coating layer can become detached from the substrate. In this study, we fabricated rapid-prototyped polycaprolactone (PCL)/β-TCP composite scaffolds, and to increase the biological properties of the composite scaffold, we used a simple coating process to reinforce the scaffolds with a mixture of collagen/HA. To increase the coating efficiency of the collagen/HA, we embedded electrospun PCL nanofibers in the composite scaffold. The fabricated scaffolds were assessed for not only physical properties including surface roughness, tensile modulus, and water-uptake ability, but also biological capabilities by culturing osteoblast-like cells (MG63) for various HA compositions (1, 3, 5 wt %) in a 2 wt % collagen solution. By accommodating the coating process, the composite scaffolds showed enhanced water-absorption ability (12% increase) and good mechanical properties (∼35% increase of the tensile modulus), compared to the pure PCL/β-TCP composite. The results of cell viability, scanning electron microscopy, alkaline phosphatase (ALP) activity, and mineralization analyses showed that, although a small portion (0.3 vol %) of coating agent (collagen/HA mixture) was used, the cellular behavior (such as attachment spreading, proliferation, and mineralization) improved remarkably.