Five kinds of simulated body fluids were prepared according to the Ca 2+ ions concentration in body fluids of human, dog, pig, rabbit and monkey so that the different biological environments in different animals were simulated. Results showed that Ca 2+ can induce bone-like apatite formation in a dose-dependent manner; there is a threshold of Ca 2+ local concentration for the formation of bone-like apatite. The threshold of Ca 2+ for bone-like apatite formation in static stimulated body fluid (SBF) is different from dynamic SBF. The threshold of static SBF is lower than that of dynamic SBF. The threshold of Ca 2+ local concentration is 0.2459g/L in static SBF and 0.3392g/L in dynamic SBF.

US and/or MBs could be used safely to enhance the delivery of NPs loading siRNA to rat RPE-J cells. A combination of the chemical (mPEG-PLGA-PLL NPs loading siRNA) and physical (US) approaches could more effectively downregulate the mRNA and protein expression of PDGF-BB.

Bone-like apatite formation on porous calcium phosphate ceramics was investigated in static simulated body fluid (SBF) and dynamic SBF at different flowing rates. The results of a 14-day immersion in static SBF showed that the formation of bone-like apatite occurred both on the surface and in the pores of the samples. When SBF flow at the physiological flow rate in muscle (2 ml/100 ml min1), bone-like apatite could be detected only in internal surface of the pores of samples. The result that bone-like apatite formation could only be found in the pores when SBF flown at physiological flow rate was consistent with that of porous calcium phosphate ceramics implanted in vivo: osteoinduction was only detected inside the pores of the porous calcium phosphate ceramics. This result implicates that the bone-like apatite may play an important role in the osteoinduction of Ca-P materials. The dynamic model used in this study may be better than usually used static immersion model in imitating the physiological condition of bone-like apatite formation. Dynamic SBF method is very useful to understand bone-like apatite formation in vivo and the mechanism of ectopic bone formation in calcium phosphate ceramics.