posted on 2016-02-21, 16:17authored byDaniel
O. Costa, S. Jeffrey Dixon, Amin S. Rizkalla
Nanoscale hydroxyapatite (HA) is an optimal candidate
biomaterial
for bone tissue engineering because of its bioactive and osteoconductive
properties. In this study, micro- and nanoscale HA particles with rod-
and wirelike morphology were synthesized by a novel sol–gel–hydrothermal
process. Sol–gel chemistry was used to produce a dry gel containing
amorphous calcium phosphate (ACP), which was used as a precursor material
in a hydrothermal process. The sol–gel–hydrothermal
products were characterized by scanning electron microscopy (SEM),
X-ray diffraction (XRD), and Fourier transform infrared spectroscopy
(FTIR) to determine particle morphology, crystal structure, and the
presence of chemical functional groups. A pure HA crystal was synthesized,
which underwent both one- and three-dimensional growth, resulting
in tunable microrod and nanorod, and wire morphologies. The effects
of solution pH and reaction time on particle diameter and length were
assessed. Particle diameter ranged from 25 to 800 nm and decreased
with an increase in solution pH, whereas both particle length and diameter
increased as the hydrothermal process was prolonged. Nanowire HA powders
(10–50 wt %) were mixed with poly(ε-caprolactone) (PCL)
to produce PCL/HA composites. Fracture surfaces of PCL/HA composites
showed a well-dispersed and homogeneous distribution of HA nanowires
within the PCL matrix. Mechanical testing revealed a significant (p < 0.05) increase in the Young’s and compressive
moduli of PCL/HA composites compared to PCL alone, with 50 wt % HA
producing a 3-fold increase in Young’s modulus from 193 to
665 MPa and 2-fold increase in compressive modulus from 230 to 487
MPa. These HA nanowires can be used to reinforce polymer composites
and are excellent biomaterials for tissue engineering of bone.