PLGA/TiO₂ Nanotube Bioactive Composite as a Novel Scaffold for Craniofacial Tissue Engineering: in vitro and in vivo Studies

Objectives: The aim of this study was to synthesize and characterize novel 3D porous scaffolds made of PLGA/TiO₂ nanotube bioactive composite microspheres for craniofacial tissue engineering.
Methods: The 3D mixed scaffolds were fabricated through a sintered microsphere technique. The PLGA/TiO₂ nanotube microspheres were packed densely in a stainless mold (cylindrical shape with a length to diameter ratio of 2:1; 10 mm in length and 5 mm in diameter) and sintered above the glass transition temperature of PLGA for a predetermined time. The mechanical properties of the scaffolds that were produced in the different sintering temperatures (80, 100 and 120°C) and times (2, 3 and 4 hours) were evaluated. In order to examine the effect that TiO₂ nanotubes have on the biodegradation behavior of the scaffolds, they were immersed in SBF for a period of 1, 2, 3, 4 and 5 weeks. Also, the in vitro (MTT assay and ALP activity) and in vivo assessments of the prepared scaffolds were studied.
Results: The incorporation of TiO₂ nanotubes greatly increased the mechanical properties of PLGA/TiO₂ nanotube microsphere-sintered scaffolds. The obtained results revealed that the PLGA/0.5 wt% TiO₂ nanotube scaffold sintered at 100°C for 3 h had the best mechanical properties as well as a proper pore structure for bone tissue engineering. Biodegradation test demonstrated that weight loss percentage of PLGA scaffolds was greater than that of PLGA/0.5 wt% TiO₂ nanotube composites. During in vitro testing, TiO₂ nanotubes improved the bioactivity of PLGA while also preventing a pH drop in the surroundings by limiting PLGA degradation. The presence of TiO₂ nanotubes also promoted cell attachment and improved the spreading of osteoblasts. Moreover, MTT assay results showed higher cell viability for PLGA/0.5% TiO₂ nanotube composite scaffolds in comparison to the control group. In vivo studies showed the amount of bone formation for PLGA/TiO₂ nanotube was approximately twice that of pure PLGA.
Conclusions: Our research suggests that PLGA/TiO₂ nanotube composites utilize the appealing bioactivity of TiO₂ nanotubes as well as the outstanding mechanical properties of PLGA, and therefore could be a promising scaffold for craniofacial tissue engineering.