Preparation, characterization and properties of nano-hydroxyapatite/polypropylene carbonate biocomposite

The combination of nano-hydroxyapatite (n-HA) and polypropylene carbonate (PPC) was used to make a composite materials by a coprecipitation method. The physical and chemical properties of the composite were tested. Scanning electron microscope (SEM) observation indicated that the biomimetic n-HA crystals were uniformly distributed in the polymer matrix. As the n-HA content increased in the composite, the fracture mechanism of the composites changes from gliding fracture to gliding and brittle fracture. Furthermore, the chemical interaction between inorganic n-HA and polypropylene carbonate was also investigated and discussed in detail. The hydrogen bonds might be formed between -OH/CO3(2-) of n-HA crystal and the ester group (-COO-) of PPC. The tensile strength of n-HA/PPC (40/60) was similar to that of the cancellous bone, and reached ca 58 MPa. The osteoblasts were cultured for up to 7 days, and then the adhesion and proliferation of osteoblasts were measured by Methyl thiazolyl tetrazolium (MTT) colorimetry assay and SEM. The cells proliferated, grew normally in fusiform shape and well attached. The in vitro test confirmed that the n-HA/PPC composites were biocompatible and showed undetectable negative effect on osteoblasts. In vivo implantation of the composite in New Zealand white rabbits was performed. It can stimulate the growth of a new bone, and at the same time the material begins to degrade. These results suggested that the composite may be suitable for the reparation or replacement of bone defects and possessed the potential for clinical applications.