Hydroxyapatite-coated polycaprolacton wide mesh as a model of open structure for bone regeneration.

In principle, three-dimensional (3D) osteoconductive grafts with a proper chemical composition, high total porosity, and fully interconnected pores are suitable carriers to provide a proper substrate for in vivo neobone tissue ingrowth. However, most porous materials carry some intrinsic limits because of their internal structure (i.e., limited macroporosity and small pore interconnection size), representing a physical constraint for a massive blood afflux and bone ingrowth and therefore for generating effective osteopermissive grafts. We therefore hypothesized that an unconventional scaffold, based on an "open-structure" concept, should not pose any limit to vascularization of grafts and consequently to the amount of bone growth. Starting from this hypothesis, we have designed and developed a 3D osteoconductive polymeric-based wide-net mesh. Polymer fibers, joining hydroxyapatite beads, were coated with a thin layer of calcium phosphate (Ca-P), coupling the osteoconductivity properties of Ca-P with the handness and bulk properties of polymers. This completely open 3D scaffold prototype was tested both in vitro and in vivo, displaying a promising in vivo blood vessel invasion and bone-forming efficiency.