Incorporating nanoplate-like hydroxyapatite into polylactide for biomimetic nanocomposites via direct melt intercalation

Abstract Natural apatite in human bones is nanoplate shaped. However, nanocomposites with nanoplate-like hydroxyapatite (np-HAp) have been poorly exploited. Herein, polylactide (PLA) nanocomposites reinforced with biomimetic np-HAp were fabricated by exfoliating laminated hydroxyapatite via direct melt intercalation method which was realized using scalable extrusion and injection molding processes. The physicochemical properties of the resulting np-HAp/PLA nanocomposites were characterized with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and mechanical testing. In addition, the biocompatibility and in vitro bioactivity were systematically investigated. The influence of np-HAp content on mechanical properties, thermal stability, hydrophilicity, and particularly biocompatibility and in vitro bioactivity were evaluated. It is found that the np-HAp/PLA nanocomposites not only show improved mechanical properties and thermal stability, but also exhibit improved cell spreading and proliferation. More importantly, the np-HAp/PLA nanocomposites exhibit excellent in vitro bioactivity due to the biomimetic nanoplate shape that has large surface area and abundant exposed active sites than other HAp shapes. It has been demonstrated that such unique nanocomposites show promising as a new biomaterial for load-bearing orthopedic implants.