In vitro bioactivity of bioresorbable porous polymeric scaffolds incorporating hydroxyapatite microspheres

Biomimetic composites consisting of polymer and mineral components, resembling bone in structure and composition, were produced using a rapid prototyping technique for bone tissue engineering applications. Solid freeform fabrication, known as rapid prototyping (RP) technology, allows scaffolds to be designed with pre-defined and controlled external and internal architecture. Using the indirect RP technique, a three-component scaffold with a woodpile structure, consisting of poly-l-lactic acid (PLLA), chitosan and hydroxyapatite (HA) microspheres, was produced that had a macroporosity of more than 50% together with micropores induced by lyophilization. X-ray diffraction analysis indicated that the preparation and construction of the composite scaffold did not affect the phase composition of the HA. The compressive strength and elastic modulus (E) for the PLLA composites are 0.42 and 1.46 MPa, respectively, which are much higher than those of chitosan/HA composites and resemble the properties of cellular structure. These scaffolds showed excellent biocompatibility and ability for three-dimensional tissue growth of MC3T3-E1 pre-osteoblastic cells. The pre-osteoblastic cells cultured on these scaffolds formed a network on the HA microspheres and proliferated not only in the macropore channels but also in the micropores, as seen from the histological analysis and electron microscopy. The proliferating cells formed an extracellular matrix network and also differentiated into mature osteoblasts, as indicated by alkaline phosphatase enzyme activity. The properties of these scaffolds indicate that they can be used for non-load-bearing applications.