Wet chemical synthesis of strontium-substituted hydroxyapatite and its influence on the mechanical and biological properties

Strontium is used orally in the medical treatment of osteoporosis because of its stimulative effect on bone formation and, simultaneously, its inhibiting effect on bone resorbing cells. Due to these effects, it might also be used for calcium phosphate-based bone substitutes. We hypothesise that strontium-substituted hydroxyapatite can be synthesised using a wet chemical reaction and a subsequent thermal treatment. Up to 15 wt% of strontium was successfully incorporated into the lattice of hydroxyapatite without affecting the apatite structure. Higher concentrations led to a destabilisation of the structure and the formation of β-tricalcium phosphate as a secondary phase. The bending strength of the composite materials was up to 30 MPa, independent of the strontium content. Initial cell culture experiments proved the cytocompatible behaviour of the material. We therefore conclude that strontium-substituted hydroxyapatite can be synthesised with suitable biological and mechanical properties as potential bone substitute material for osteoporotic patients.