Spark plasma sintered hydroxyapatite/graphite nanosheet and hydroxyapatite/multiwalled carbon nanotube composites: Mechanical and in vitro cellular properties

Hyroxyapatite (HA) and its nanocomposites reinforced with 0.5, 1, 1.5, and 2wt% graphite nanosheets (GNs) and multi-walled carbon nanotubes (MWNTs) are fabricated by means of spark plasma sintering (SPS) process. The effects of MWNT and GN additions on the morphology, mechanical behavior, cell adhesion, and biocompatibility of HA were studied. Three-point-bending test shows that the bending strength of MWNT/HA nanocomposites increases with increasing MWNT content. However, the bending strength of GN/HA nanocomposites initially increases by adding 0.5wt% GN, and then decreases markedly as the filler content increases. Cell culture and viability test results demonstrate that the GNs with diameters of several micrometers retard osteoblast cell adhesion and proliferation on the GN/HA nanocomposite. In contrast, the addition of 2wt% MWNT to HA is beneficial to promote osteoblast adhesion and proliferation, thereby enhancing the biocompatibility of MWNT/HA nanocomposite. Bending test is used to evaluate the bending strength of spark plasma sintered hydroxyapatite (HA)-based composites reinforced with low loading levels of multi-walled carbon nanotubes (MWNTs) and graphite nanosheets (GNs). The bending stress of MWNT/HA nanocomposites increases markedly with increasing filler content. In contrast, the bending stress of GN/HA nanocomposites reaches an apparent maximum at 0.5wt% GN, thereafter decreases continuously with increasing filler content. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA.