Preparation and characterization of aliphatic polyurethane and modified hydroxyapatite composites for bone tissue engineering

Surfaces of nano-hydroxyapatite (n-HA) particles were modified by grafting of etidronic acid (ETD, 0.1 M) and were reinforced into polyurethane scaffolds prepared by foaming method to develop porous modified nano-hydroxyapatite/polyurethane (m-HA/PU) nanocomposite scaffolds for bone tissue engineering. Particle size and morphology of nanoparticles were studied using X-ray diffraction, transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. TEM and SEM results revealed that the surface of obtained modified hydroxyapatite (m-HA) particles was completely changed from grain- to plate-type structure with the size of 40 nm. Chemical structure, mechanical properties and biomedical application were studied using Fourier transform infrared spectroscopy (FTIR), universal testing machine and in vitro studies. In FTIR spectra, disappearance of peak around 2270 cm⁻¹ confirmed the formation of polyurethane nanocomposite scaffolds and bands in the spectral range of 1400 and 800–900 correspond to the presence of calcium and phosphate groups due to hydroxyapatite. As the concentration of m-HA increased from 0 to 30 wt%, the compressive strength of the resulting PU/m-HA nanocomposites increased from 0.094 to 22.4 MPa. In vitro study with simulated body fluid (SBF) for 4 weeks indicated that surface was partially hydrolysed. Cell culture study showed that m-HA/PU nanocomposite scaffold is well suited for application in bone tissue engineering.