Graphene Oxide-Templated Synthesis of Hydroxyapatite Nanowhiskers To Improve the Mechanical and Osteoblastic Performance of Poly(lactic acid) for Bone Tissue Regeneration

Central to the design and development of biomedical-adaptive graphene oxide (GO) is functional modification of GO amenable to technologically reliable and economically viable processing. Here we describe a high efficiency and low-temperature approach to in situ synthesis of hydroxyapatite (HA) nanowhiskers at GO surfaces (HA@GO), strategically involving microwave-assisted mineralization in stimulated body fluid at room temperature. Being preferentially nucleated and accommodated at GO surfaces, the highly crystalline HA nanowhiskers with an average diameter of 20 nm and a length of 150 nm were characterized by coherent bonding with the host nanosheets. The strong GO HA interactions, combined with the high density of oxygen functional groups, endowed the HA@GO with good exfoliation and dispersion in a poly(lactic acid) (PLA) matrix even at the highest filler content of 30 wt % (HG30). Inheriting the excellent biocompatibility of HA and the remarkable strength of GO, the PLA/HA@GO nanocomposites exhibited an unusual combination of prominent cytocompatibility with osteoblast cells and high mechanical strength and toughness. In particular, compared to that of the normal PLA/HA counterpart, HG30 exhibited a >85% increase in cell viability, accompanied by 2- and 7.9-fold increases in tensile strength and toughness (105 MPa and 2.9 MJ/m(3)), respectively. This work paves a facile yet effective way to GO functionalization with biologically beneficial HA nanowhiskers, which may prompt the realistic development of GO-based biomaterials, especially in the realm of polymer/GO nanocomposites.