COMPOSITION–PROPERTY RELATIONSHIPS IN MULTICOMPONENT GERMANIUM–BASED POLYALKENOATE CEMENTS
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Vertebral compression fractures are increasingly treated through minimally invasive, rather than surgical, procedures due to the draw of improved outcomes and reduced risk of infection. Conventional clinical materials fail to balance excellent biocompati- bility with appropriate mechanical properties. Glass polyalkenoate cements (GPCs) show significant potential to overcome this restraint, however they have been avoided in non–dental applications because Al3+ has been implicated in localized poor bone mineralisation and neurotoxicity. Aluminum–free glass polyalkenoate cements fall short of ideal clinical injectability (6 to 10 minutes) and basic mechanical property needs (compressive strength >30 MPa). The synthesis of germanium (Ge) containing glasses has ameliorated this limitation and has provided new GPCs with clinically useful characteristics. However, it is unknown whether the Ge modifications may compromise biocompatibility. This study examines 12 multicomponent glasses with varying silicon:germanium molar ratios and their contiguous polalkenoate cements. Glasses were melt-quenched (1520C, 1hr, ground to <45 μm) and subjected to thermogravimetric analysis (TGA) and x–ray diffraction (XRD), then blended with 50 wt % H2O polyacrylic acid (2:1.5) and set in Teflon molds. Design of Mixtures (DoM) regression analyses were used to examine composition–property relationships with respect to temporal ion release and NIH 3T3 mouse fibroblast cytocompatibility of extracts derived from these glasses and cements, paying particular attention to germanium given its potential toxic characteristics. The results of this investigation have shown that cell viability remained between 92 to 124 % for the glasses, and between 94 to 105 % for all setting cements. [Ge4+], [Si4+], [Na+] and [Sr2+] ion release were detected up to 370 ppm, 12 ppm, 110 ppm and 20 ppm, respectively, for glasses and up to 200 ppm, 45 ppm, 32 ppm and 5 ppm, respectively, for cements. An optimization validation was performed based on the acquired data; this study has shown that the composition produced (0.36ZnO2 − 0.04SrO2 − 0.021SiO2 − 0.459GeO2 − 0.0095ZrO2 − 0.0095Na2O − 0.101CaO) gives equivalent characteristics to a previously developed germanium–containing composition (DG 209) with respect to ion release but possesses inferior mechanical characteristics. DG 209 is a promising GPC material for further investigation.