Bioactive calcium phosphate foam ceramics modified by biomimetic apatite

Abstract

By combining the method of replication of polyurethane foam matrices at 1200 °C and modification in model SBF (Simulated Body Fluid) solutions of various compositions, open-pore calcium phosphate foam ceramics with a porosity of 53-60 % was obtained. The architecture and morphology of the calcium phosphate foam ceramics surface was formed by using polyurethane foam matrices («Granufoam», «STR») with different porosity and quantity of open pores. Modification of the calcium phosphate foam ceramics in SBF solutions of various compositions leads to a slight decrease in porosity to 3 %, which indicates the formation of an ultrathin apatite layer. The calcium phosphate-modified foam ceramics consisted of β-tricalcium phosphate, β-calcium pyrophosphate, α-tricalcium phosphate, and biomimetic apatite. In the standard SBF solution, the formation of apatite on calcium phosphate foam ceramics occurs slowly (14-56 days) and the strength increases by a factor of 2 as compared to the initial one. Soaking of calcium phosphate foam ceramics in SBF without HCO3- leads to the formation of biomimetic apatite with inclusions of calcium chloride dihydrophosphate in spherulites. Modification in a 5-fold concentrated SBF solution for 3-5 days at 37 °C makes it possible to form 6-10 times more biomimetic apatite compared to standard SBF with a 2.5-fold increase in static strength to 0.05 MPa. It has been established that at 800 °C biomimetic apatite crystallizes into β- tricalcium phosphate.