Material Characteristics And Biocompatibility Of A β-tricalcium Phosphate/Polycaprolactone Composite Scaffold For Bone Regeneration

The requirements of an ideal scaffold are sufficient porosity and pore dimensions with better interconnectivity to promote initial cell attachment and tissue ingrowth, biocompatibility, biodegradability, and higher mechanical strength. In addition, the scaffold should exhibit a comparable degradation rate and mechanical properties with the targeted tissue. Beta tricalcium phosphate (β-TCP) has excellent biocompatibility, osteoconductivity, and biodegradability. The β-TCP scaffold has low mechanical strength because of its porous structure. Polycaprolactone (PCL) is a biodegradable polymer with elastic characteristics and excellent biocompatibility. The objectives of this study are: (i) fabrication of α-TCP scaffolds by a polymeric reticulate method and to coat them with PCL to prepare β-TCP/PCL composites; (ii)to investigate their morphology, phase content, mechanical properties and biodegradation; and (iii) to assess adhesion,proliferation,and differentiation of MC3T3-E1 osteoblast cells on these scaffolds under in vitro conditions. β-TCP scaffold was fabricated by replica method using polyurethane (PU) foam as a passing material. Commercial 3 -TCP power (35 g and 40 g) was mixed with poly vinyl butyl (PVB), and triethyl phosphate (TEP) in 100 ml of ethanol to prepare a slurry.The PU foam was fully immersed in the β-TCP slurry for 2 min. The excess β-TCP was removed by blowing with an air gun and the sponge was dried at 80 ℃ for 5 min. The dipping- and drying- steps were repeated for 3 cycles and stored in a desiccator for 24 h. The green body of scaffold was heat-treated at 600 ℃ for 3 h and again at 1300 ℃ for 3 h to burn out the PU foam and to enable sintering. The β-TCP scaffold was coated with PCL to improve its mechanical properties. PCL pellets were dissolved in dichloromethane with the concentration of 2.5 %, 5.0 % and 7.5 %w/v, respectively. Sintered β-TCP scaffolds were immersed into the PCL solution for 30 min and then dried at 25 ℃ for 24 h to prepare the PCL coated β-TCP scaffolds. The β-TCP and PCL coated β-TCP scaffolds were characterized for their morphology by field emission scanning electron microscope, phase content by X-ray diffraction measurement, mechanical properties in terms of bending and compression strength using an Instron machine and biodegradation behaviour by 4 immersion in Tris buffer. The cytotoxity and differentiation of these scaffolds were examined by MTT assay and ALP assays. The surface morphology of the β-TCP scaffold showed the presence of interconnected pores with their pore size ranging from 150 to 950 um. When coated with PCL, more surfaces of β-TCP scaffolds were covered with the PCL coating while some of the pores were partially clogged.The PCL coating improved the compression and bending strength of β-TCP scaffolds by two times. The degradation rate of β-TCP scaffold in Tris buffer was faster than that of the PCL coated β-TCP scaffold. MTT and ALP assays showed that MC3T3-E1 osteoblast cells could proliferate and differentiate well on both PCL coated as well as uncoated β-TCP scaffolds. Based on the comprehensive analysis made in this study, it is concluded that the β-TCP/PCL composite scaffolds fabricated using 40% TCP and 5% PCL exhibits optimum properties suitable for biomedical applications.