Ion-Release from novel Boron and Fluorine-containing bioactive glasses

Ion-release profiles from bioactive glasses provide fundamental information concerning their potential use as biomaterials.

Objective: In view of the known relationship between apatite growth and ion release, we examined the change in concentration of Ca⁺² and PO₄^-3 upon soaking novel sol-gel bioactive glasses that contain boron and fluoride, in simulated body fluid (SBF).

Methods: BAGs were prepared by sol-gel methods with the following compositions: 65%SiO₂-31%CaO-4%P₂O₅ (BAG-1); 75%SiO₂-21%CaO-4%P₂O₅ (BAG-2); and 85%SiO₂-11%CaO-4%P₂O₅ (BAG-3); 84%SiO₂-31%CaO-4%P₂O₅-1%B₂F₃ (BAG-4); 64%SiO₂-31%CaO-4%P₂O₅-1% B₂F₃ (BAG-5); 80%SiO₂-11%CaO-4%P₂O₅-1%B₂O₃ (BAG-6). Samples (10 ± 0.5 mg) were immersed in 3 mL SBF with continuous agitation at 37 °C. Changes in Ca⁺² and PO₄^-3 were measured over time intervals ranging from 15 min to 14 days with the use of ion-selective electrode and visible-spectrophotometric methods, respectively. Data were compared using ANOVA with significance set at 0.05.

Results: In all cases we observed a significant increase in the Ca⁺² concentrations above that of SBF; the rate and magnitude of change correlated closely with the Ca content in the native BAG. The differences were significant for BAGs containing 31% Ca compared to those containing 21% and 11%. Concurrent measurements of the changes in PO₄^-3 concentrations showed that, in all cases, the PO₄^-3 levels rapidly decreased within the first day to an undetectable (< 1 ppm) level. Conclusion: The rate and quantity of Ca⁺² released for these BAGs are directly related to the Ca composition of the starting glass. The addition of boron and fluoride did not affect the ion release profiles. These results may lead to the ability to tailor these qualities of the BAGs for specific applications, either by adjusting the percentages of Si, Ca, and P, or by preparing mixtures of various compositions.