Preliminary in vitro biological evaluation (cytocompatibility and degradation products) of vertebroplasty cement candidates

Dickinson, Victoria (School of Biomedical Engineering, Dalhousie University)
Boyd, Daniel (Dept. of Applied Oral Sciences and School of Biomedical Engineering, Dalhousie University)
Zhang, Xiao Fang (Dept. of Applied Oral Sciences, Dalhousie University)


Aluminum free glass-ionomer cements (GICs) show promise in orthopaedic applications (in particular vertebroplasty), but are limited by an inability to balance the necessary levels of injectability with mechanical properties. Recently we have shown that Ge-modified GICs ameliorate this limitation [1]. Such materials are injectable for up to 10minutes and have improved mechanical properties versus conventional aluminum free GICs. However, the compositional modification (addition of Ge to the glass phase) may compromise biological performance [2]. This study evaluates and correlates the cytocompatibility of Ge-containing GICs with their degradation by-products. In addition, composition-property relationships are modeled using regression analysis to commence biological evaluation of the materials.

Materials and Methods

Twelve multicomponent glasses (Table 1) were melt-quenched and ground to sub-45 micron powder. Glasses were mixed with 50wt% polyacrylic acid at a fixed glass to acid ratio (G:A) of 2:1.5 and set in Teflon® molds. Cement specimens were incubated at 37°C in tissue culture water for 1, 7 and 30 days. Filtered extracts were evaluated in triplicate for cell viability via MTT assay using an NIH 3T3 mouse fibroblast cell line and analyzed against a tissue culture water and commercial cement (SpinePlex®) controls. Ge4+, Zn2+ and Sr2+ levels were determined through inductively coupled plasma atomic emission spectroscopy. StatEase Software was used to build regression models for composition-property relationships [1].


Excepting DG204, all cements showed cell viability exceeding 90%. Cell viability results for all twelve glass extracts at three experimental time points are listed in Table 2. Germanium ion extract levels for three time points are listed in figure 1. Ge4+, Sr2+ and Zn2+ levels were recorded up to 200, 60 and 5 ppm, respectively after 30 days. Regression analysis identified potential composition-property relationships.

Discussion and Conclusion

All vertebroplasty cement candidates, excepting DG204, were found to be cytocompatible. Variations of therapeutic and potentially therapeutic ion levels among cements did not significantly impact their cell viability.

Table 1: Molar Compositions of the Glasses

Table 2: Cell Viability Results

Figure 1: Ge Glass Extract Concentrations


1. Dickey, B.T., Kehoe, S., Boyd, D., paper under review, Journal of Mechanical Behaviour of Biomedical Materials (January 24, 2013). 2. Murphy, S., et al., Journal of Materials Science – Materials in Medicine (2010), 21(10): 2827-2834.

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