Iron oxide nanoparticles significantly enhances the injectability of apatitic bone cement for vertebroplasty.
METHODS
Experimental study to characterize the setting and the cytocompatibility properties of apatitic bone cement.


OBJECTIVE
To investigate the setting, flowing, and biocompatibility properties of new iron-modified calcium phosphate bone cements.


BACKGROUND
Vertebroplasty and kyphoplasty are efficient procedures for the treatment of painful vertebral compression fractures. Nowadays, calcium phosphate cements are used to treat these fractures mainly due to the similar bone apatitic phase formed after setting. However, clinicians have reported great difficulties in filling the vertebral bodies due to the high pressures needed to inject these materials. Thus, new approaches are needed to improve the initial flowing properties of these cements without affecting or even improving their short-term mechanical stability and their long-term in vivo cement transformation into bone tissue.


METHODS
Cement setting times were measured by the Gillmore needles method. The evolution of the compressive strength accounted for the cement hardening process. Scanning Electron Microscopy followed the evolution of the cement microstructure with hardening. Radiograph diffraction analysis confirmed the evolution of the crystalline phases underlying the setting and the hardening processes. Injectability tests were performed by using syringes filled with bone cement and recording the evolution of the injection force needed to empty the syringe. Finally, the cytocompatibility was analyzed by culturing human epithelial cells onto the cements and evaluating both the relative cell viability and the adhesion cell density.


RESULTS
The modification of the powder phase of an alpha-tricalcium phosphate cement with iron oxide nanopar-ticles significantly enhanced, at constant liquid to powder cement mixing ratio, the resulting cement injectability by lowering the extrusion force required for cement delivery. For example, 24 wt% iron oxide addition resulted in 83% of cement injected with an extrusion force lower than 25 N. In fact, the setting and the working times of the cement pastes increased with iron oxide addition. Moreover, the new cement pastes showed improved compressive strength in agreement with the crystalline microstructure evolved during hardening. However, iron modification did not produced cytotoxic cements as compare to nonmodified cements.


CONCLUSIONS
It has been shown that the addition of iron oxide nanoparticles into the powder phase of an alpha-tricalcium phosphate based cement improved both, the initial injectability and maximum compressive strength of the cement without affecting their physico-chemical setting reactions and their cytocompatibility. These results could be further exploited by designing improved injectable apatitic cements with suitable mechanical properties and in vivo cement transformation ratios into bone tissue by incorporating phases creating porosity.
Vlad
María Daniela
MD
Interdepartment Research Group for the Applied Scientific Collaboration, Division of Biomaterials and Bioengineering, Technical University of Catalonia, UPC, Barcelona, Spain.
del Valle
Luis J
LJ
Barracó
Marc
M
Torres
Ricardo
R
López
José
J
Fernández
Enrique
E
D001031:Apatites / Q000008:administration & dosage* / Q000737:chemistry; D001843:Bone Cements / Q000737:chemistry; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D019245:Compressive Strength; D005290:Ferric Compounds / Q000008:administration & dosage* / Q000737:chemistry; D006801:Humans; D008422:Materials Testing / Q000379:methods; D053758:Nanoparticles / Q000008:administration & dosage* / Q000737:chemistry; D014407:Tumor Cells, Cultured; D054854:Vertebroplasty / Q000379:methods
D001031:Apatites; D001843:Bone Cements; D005290:Ferric Compounds; C000499:ferric oxide