Preparation and assessment of revised simulated body fluids

A simulated body fluid (SBF) with ion concentrations approximately equal to those of human blood plasma has been used widely for in vitro assessment of the bioactivity of artificial materials and for the formation of bone-like apatite on various substrates. The ion concentrations of a conventional SBF (c-SBF) are, however, not exactly equal to those of blood plasma. In the present study, a revision of c-SBF was made to prepare new SBFs (r-SBF, i-SBF, and m-SBF) with ion concentrations equal to or closer to those of blood plasma. The ion concentrations of the r-SBF and i-SBF were designed to be equal to those of blood plasma in total and dissociated amounts, respectively. The m-SBF was designed to have a total ion concentration equal to that of blood plasma, except for the concentration of HCO(-) (3), which was set to the saturated level with respect to calcite. The ion concentrations and pH of the as-prepared new SBFs were found to be equal to those of the nominal values. Upon sealed storage, the r-SBF and i-SBF showed no change in ion concentrations for up to 4 weeks at 5 degrees C, and up to 2 weeks at 36.5 degrees C, but thereafter they showed a decrease in HCO(-) (3) concentration and an increase in pH. Under the same storage conditions, the c-SBF and m-SBF showed no change in ion concentrations and pH values over a period of up to 8 weeks. These results indicate that the r-SBF and i-SBF are less stable than the c-SBF and m-SBF in terms of changes in ion concentrations relative to storage period. The m-SBF is optimal for in vitro bioactivity assessment of artificial materials and for biomimetic production of bone-like apatite.