Incorporation of multi-walled carbon nanotubes to PMMA bone cement improves cytocompatibility and osseointegration

Acrylic bone cement (ABC) has been used as a grouting agent in joint replacement surgery for over 50 years. In particular, ABC is irreplaceable for high-load joint replacement such as total hip joint replacements (THJRs) and total knee joint replacements because of its excellent mechanical properties. However, the bioactivity of ABC needs to be improved. In this study, we attempted to enhance cytocompatibility and osseointegration of polymethyl methacrylate (PMMA) bone cement via the incorporation of multi-walled carbon nanotube (MWCNT) powders. The results of in vitro rat bone marrow mesenchymal stem cells (rBMSCs) culture on the specimens of PMMA containing different levels of MWCNT loading demonstrated that MWCNT addition improved cell adhesion and proliferation. Furthermore, it was shown from both gene and protein expression levels that MWCNT addition promoted the osteogenic differentiation. For the animal model study, PMMA specimens at different levels of MWCNT loading were implanted into a New Zealand rabbit bone defect model. The results showed that new bone formation occurred inside the bone cement and the integration between the bone cement and bone tissue were significantly enhanced with an increase in MWCNT loading level at 12 weeks post-surgery. Moreover, when the loading of MWCNT was only 1 wt%, the bone ingrowth ratio was up to 42.2% at 12 weeks, and a large number of osteoblasts congregated and new bone formed within the bone cement. In conclusion, cytocompatibility and osseointegration of the bone cements can be controlled by adjusting the MWCNT loading. The whole collection of the present results suggests that MWCNT-incorporated PMMA bone cement may have promise for use in certain orthopedic applications.