A hybrid PHB-hydroxyapatite composite for biomedical application: production, in vitro and in vivo investigation

Samples of a hybrid composite of polyhydroxybutyrate (PHB), a biodegradable polyester, and hydroxyapatite (HA), with different PHB/HA ratios, have been prepared using mechanical-physical method. Electron microscopy, X-ray structure analysis and differential thermal analysis have been used to investigate the structure and physicochemical properties of the composite, depending on the PHB/HA ratio. The properties of the surface of the HA-loaded composite are significantly different from those of the pure polymer. As the HA percentage in the composite increases, free interface energy, the cohesive force, i.e., the strength of the adhesive bond between the composite surface and the water phase, and surface wettability increase. The HA percentage of the composite does not influence its melting temperature, but affects the temperature for the onset of decomposition: as the HA content increases from 0 to 10% (w/w), Td decreases from 260 degrees C to 225 degrees C. The degree of crystallinity of PHB/HA increases from 77% to 89% with an increase in the HA fraction from 10% to 50%. Functional properties of the composites have been investigated in vitro and in vivo. The best parameters of growth and differentiation of murine marrow osteoblasts are registered on PHB/HA samples containing 10% and 20% HA. In ectopic bone formation assay it has been proven that the hybrid PHB/HA composites can function as scaffolds and that bone tissue develops on their surface and in pores.