PLLA Scaffold via TIPS for Bone Tissue Engineering

Abstract

Tissue engineering offers a promising new approach to repair bone fractures, fractures that do not heal, and fractures due to bone tumors. In this work, two different approaches were tested in order to obtain Poly-LLactic Acid (PLLA) porous scaffolds via Thermally Induced Phase Separation (TIPS) for bone tissue engineering application. First, the possibility to produce a composite material, by incorporating Hydroxyapatite (HA) particles in a Poly-L-lactic acid (PLLA) matrix was investigated. Two PLLA/HA weight ratios (70/30 and 50/50) were tested. The results showed that the presence of HA does not influence the phase separation process, i.e. the composite scaffolds microstructure is similar to pure PLLA scaffolds. WAXD analysis confirmed the full incorporation of HA particles into the polymer matrix. Moreover, compression tests showed a fourfold increase of Young module with respect to pure PLLA scaffold. Since the production of scaffolds for bone tissue regeneration is a challenging target, scaffolds must mimic the bone morphology, thus requiring a gradient of pore dimension and morphology along one dimension. To attain this goal, the second part of the work describes the design, set up and test of an experimental apparatus able to set different thermal histories on the two sides of a sample. Scaffolds were produced by following various thermal protocols on both sample surfaces. The results showed that through this technique it is possible to produce scaffolds with a pore size that increases along sample thickness. As a matter of fact, the obtained average pore dimension on one side of the sample was about 70 μm, whereas it was around 240 μm on the opposite surface. By moving along the sample thickness, the pore dimension increased steadily. All things considered, a reliable route for the production of composite PLLA/HA scaffolds with a controlled pore size distribution was assessed, thus offering a valid support to bone tissue engineering.