Compressive mechanical properties, deformation mechanism and bioactivity of bioactive ceramics filled PLLA composite scaffolds

A biodegradable thermoplastic polymer poly (L-lactide) (PLLA) have been used to develop bioabsorbable polymeric scaffolds for bone tissue regeneration, however, it is known that the lack of bioactivity causes biological problems such as necrosis. Therefore, bioactive ceramics such as hydroxyapatite (HAp), α-TCP and β-TCP are used to improve the bioactivity of PLLA. As a scaffold for cell growth and the following implantation, suitable mechanical properties and appropriate pore size and porosity are required so that seeded cells adapt the environment well and excrete a sufficient amount of extracellualr matricies. Furthermore, the scaffold is needed to accommodate a large number of cells and ensure the high rate of cell growth for the successful tissue regeneration. Thus, scaffolds possessing controllable mechanical properties, appropriate pore size and porosity and biological compatibility must be developed for successful achievement of bone regeneration. In this study, porous composite materials consisting of PLLA matrix with HAp, α-TCP or β-TCP fillers were developed as scaffolds for bone regeneration to improve bioactivity and mechanical properties of the standard PLLA scaffold by using the solid-liquid phase separation and the freeze-drying method. It was found that the addition of α-TCP and β-TCP fillers greater than 10wt% effectively increased the compressive modulus, while HAp did not show such improvement. The compressive strength was slightly improved by the addition of β-TCP only. Osteoblast-like MC3T3-E1 cells were also seeded and cultured in these composite scaffolds and it was found that the addition of α-TCP greatly improved the rate of cell growth compared to the other bioactive ceramics.