Strontium substitution of gelatin modified calcium hydrogen phosphates as porous hard tissue substitutes

Abstract Aiming at the generation of a high strontium‐containing degradable bone substitute, the exchange of calcium with strontium in gelatin‐modified brushite was investigated. The ion substitution showed two mineral groups, the high‐calcium containing minerals with a maximum measured molar Ca/Sr ratio of 80%/20% (mass ratio 63%/37%) and the high‐strontium containing ones with a maximum measured molar Ca/Sr ratio of 21%/79% (mass ratio 10%/90%). In contrast to the high‐strontium mineral phases, a high mass loss was observed for the calcium‐based minerals during incubation in cell culture medium (alpha‐MEM), but also an increase in strength owing to dissolution and re‐precipitation. This resulted for the former in a decrease of cation concentration (Ca + Sr) in the medium, while the pH value decreased and the phosphate ion concentration rose significantly. The latter group of materials, the high‐strontium containing ones, showed only a moderate change in mass and a decrease in strength, but the Ca + Sr concentration remained permanently above the initial calcium concentration in the medium. This might be advantageous for a future planned application by supporting bone regeneration on the cellular level.