In-vivo measurement of strontium incorporation and retention in human bone using an x-ray fluorescence system

Stronthium (Sr), found in nature and human skeleton [sic], exerts beneficial or detrimental effects, depending on levels. Previous strontium studies in humans and animals showed bone mineral density and bone strength increases. However, its exact mechanism of therapeutic action is not fully understood. The purpose of this study was to investigate strontium incorporation and retention over time, in healthy and osteoporotic/osteopenic individuals, using the non-invasive, in-vivo X-Ray Fluorescence (IVXRF) system developed and optimized by Pejovic-Milic 2004 and Zamburlini 2008. Nine individuals, self-supplementing with strontium, were recruited and measured at their finger and ankle, representing cortical and trabecular bone. Using ¹²⁵I brachytherapy seeds as the radiation photon source, each measurement lasted thirty minutes. All individuals showed an initial rapid uptake of strontium within 2-5 months followed by slower increases, suggesting that strontium incorporation and retention is a result of two different mechanisms and is dependent on the bone remodeling cycle.

In-vivo measurement of strontium incorporation and retention in human bone using an x-ray fluorescence system

Stronthium (Sr), found in nature and human skeleton [sic], exerts beneficial or detrimental effects, depending on levels. Previous strontium studies in humans and animals showed bone mineral density and bone strength increases. However, its exact mechanism of therapeutic action is not fully understood. The purpose of this study was to investigate strontium incorporation and retention over time, in healthy and osteoporotic/osteopenic individuals, using the non-invasive, in-vivo X-Ray Fluorescence (IVXRF) system developed and optimized by Pejovic-Milic 2004 and Zamburlini 2008. Nine individuals, self-supplementing with strontium, were recruited and measured at their finger and ankle, representing cortical and trabecular bone. Using ¹²⁵I brachytherapy seeds as the radiation photon source, each measurement lasted thirty minutes. All individuals showed an initial rapid uptake of strontium within 2-5 months followed by slower increases, suggesting that strontium incorporation and retention is a result of two different mechanisms and is dependent on the bone remodeling cycle.

Compositional variability of Mg/Ca, Sr/Ca, and Na/Ca in the deep-sea bivalve Acesta excavata (Fabricius, 1779)

Acesta excavata (Fabricius, 1779) is a slow growing bivalve from the Limidae family and is often found associated with cold-water coral reefs along the European continental margin. Here we present the compositional variability of frequently used proxy elemental ratios (Mg/Ca, Sr/Ca, Na/Ca) measured by laser-ablation mass spectrometry (LA-ICP-MS) and compare it to in-situ recorded instrumental seawater parameters such as temperature and salinity. Shell Mg/Ca measured in the fibrous calcitic shell section was overall not correlated with seawater temperature or salinity; however, some samples show significant correlations with temperature with a sensitivity that was found to be unusually high in comparison to other marine organisms. Mg/Ca and Sr/Ca measured in the fibrous calcitic shell section display significant negative correlations with the linear extension rate of the shell, which indicates strong vital effects in these bivalves. Multiple linear regression analysis indicates that up to 79% of elemental variability is explicable with temperature and salinity as independent predictor values. Yet, the overall results clearly show that the application of Element/Ca (E/Ca) ratios in these bivalves to reconstruct past changes in temperature and salinity is likely to be complicated due to strong vital effects and the effects of organic material embedded in the shell. Therefore, we suggest to apply additional techniques, such as clumped isotopes, in order to exactly determine and quantify the underlying vital effects and possibly account for these. We found differences in the chemical composition between the two calcitic shell layers that are possibly explainable through differences of the crystal morphology. Sr/Ca ratios also appear to be partly controlled by the amount of magnesium, because the small magnesium ions bend the crystal lattice which increases the space for strontium incorporation. Oxidative cleaning with H2O2 did not significantly change the Mg/Ca and Sr/Ca composition of the shell. Na/Ca ratios decreased after the oxidative cleaning, which is most likely a leaching effect and not caused by the removal of organic matter.

Influence of Strontium on the Physical, Mechanical and In-Vitro Bioactivity of Glass Ionomer Cements

In this work, we investigated the effects of strontium incorporation in the glass phase of glass ionomer cements (GIC). Three different glass compositions were synthesized with 0, 5, and 10 mol% of SrO addition. GICs were prepared by the addition of 50 wt% polyacrylic acid (PAA) at powder to liquid ratio of 1:1.5. Initial characterization on the cement series was to study their rheological behavior. Cements represented working times between 50-64 seconds and setting times of 356-452 seconds. Rheological results indicated that the addition of strontium decreases the working and setting times of the cements. To analyze the mechanical properties, compressive and flexural strength studies were performed after 1, 10, and 30 days incubation in simulated body fluid (SBF). The compressive strength of the cements increased as a function of incubation time, with the strontium containing compositions showing the highest strength at 34 megapascal (MPa) and after 30 days of incubation. Biaxial flexural strength of the cements was not significantly affected by the composition and maturation time and ranged between 13.4 to 16.3 MPa. In-vitro bioactivity of the cements was analyzed using SBF trials and after 1, 10, and 30 days incubation periods. Strontium containing cements, showed higher solubility with higher amounts of calcium phosphate surface depositions only after 10 days incubation. The elemental identifications of the surface depositions indicated high amounts of Ca, P and Zn are present on the surface of SBF incubated samples.

Influence of Strontium on the Physical, Mechanical and In-Vitro Bioactivity of Glass Ionomer Cements

In this work, we investigated the effects of strontium incorporation in the glass phase of glass ionomer cements (GIC). Three different glass compositions were synthesized with 0, 5, and 10 mol% of SrO addition. GICs were prepared by the addition of 50 wt% polyacrylic acid (PAA) at powder to liquid ratio of 1:1.5. Initial characterization on the cement series was to study their rheological behavior. Cements represented working times between 50-64 seconds and setting times of 356-452 seconds. Rheological results indicated that the addition of strontium decreases the working and setting times of the cements. To analyze the mechanical properties, compressive and flexural strength studies were performed after 1, 10, and 30 days incubation in simulated body fluid. The compressive strength of the cements increased as a function of incubation time, with the strontium containing compositions showing the highest strength at 34 MPa and after 30 days of incubation. Biaxial flexural strength of the cements was not significantly affected by the composition and maturation time and ranged between 13.4 to 16.3 MPa. In-vitro bioactivity of the cements was analyzed using SBF trials and after 1, 10, and 30 days incubation periods. Strontium containing cements, showed higher solubility with higher amounts of calcium phosphate surface depositions only after 10 days incubation. The elemental identifications of the surface depositions indicated high amounts of Ca, P and Zn are present on the surface of SBF incubated samples.