Strontium offers a new approach to bone replacements, thanks to recent work by French scientists.

The interdisciplinary team used sol-gel techniques to make calcium phosphate ceramics containing strontium. Jean-Marie Nedelec of Blaise Pascal University in Aubière, the leader of the research team, says that 'the anti-inflammatory properties discovered for this material and the known anti-osteoporotic effect of strontium are very interesting and promising'. He suggests that potential uses could include biomedical applications such as bone replacements, scaffolds for tissue engineering, and coating prostheses like hip replacements to enhance integration into the bone.

Calcium phosphate forms a number of different crystalline phases; the most common in bone are known as whitlockite -Ca₃(PO₄)₂ and hydroxyapatite Ca₅(PO₄)₃OH. Hydroxyapatite-based materials are already used in medical applications. It is already known that strontium ions can replace calcium in bone, and taking strontium orally can enhance bone formation and density, and provide an effective treatment for osteoporosis.

The strontium-doped materials developed by the research team have a higher proportion of whitlockite and an amorphous form than undoped calcium phosphate. These  are more soluble than hydroxyapatite and, when placed in a medium mimicking human blood plasma, releases strontium at a level that is known to have in vivo anti-osteoporotic effects. The doped material also decreases the inflammatory response of a cell culture compared to an undoped sample.

Nedelec became interested in this area from his previous work in sol-gel chemistry. The sol-gel method involves the precipitation a gel, followed by drying and processing to form a ceramic. It has many advantages such as low-temperature processing, high purity and homogeneity, control over the porosity, and ease of varying the shape of the material.

Nedelec says that future work will also study the substitution of other biologically active cations in calcium phosphates, and eventually in vivo studies of the potential applications.

Michael Townsend