Development of 3D PCL microsphere/TiO₂ nanotube composite scaffolds for bone tissue engineering

In this research, the three dimensional porous scaffolds made of a polycaprolactone (PCL) microsphere/TiO₂ nanotube (TNT) composite was fabricated and evaluated for potential bone substitute applications. We used a microsphere sintering method to produce three dimensional PCL microsphere/TNT composite scaffolds. The mechanical properties of composite scaffolds were regulated by varying parameters, such as sintering time, microsphere diameter range size and PCL/TNT ratio. The obtained results ascertained that the PCL/TNT (0.5wt%) scaffold sintered at 60°C for 90min had the most optimal mechanical properties and an appropriate pore structure for bone tissue engineering applications. The average pore size and total porosity percentage increased after increasing the microsphere diameter range for PCL and PCL/TNT (0.5wt%) scaffolds. The degradation rate was relatively high in PCL/TNT (0.5wt%) composites compared to pure PCL when the samples were placed in the simulated body fluid (SBF) for 6weeks. Also, the compressive strength and modulus of PCL and PCL/TNT (0.5wt%) composite scaffolds decreased during the 6weeks of storage in SBF. MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) assay and alkaline phosphates (ALP) activity results demonstrated that a generally increasing trend in cell viability was observed for PCL/TNT (0.5wt%) scaffold sintered at 60°C for 90min compared to the control group. Eventually, the quantitative RT-PCR data provided the evidence that the PCL scaffold containing TiO₂ nanotube constitutes a good substrate for cell differentiation leading to ECM mineralization.