Abstract
Hydroxyapatite sol (HAm), which is composed of hydroxyapatite microparticles without heating, has recently been developed as a new biomaterial. We have previously observed that HAm inhibited alkaline phosphatase activity of osteoblastic MC3T3-E1 cells in the absence of fetal bovine serum (FBS) in alpha-MEM culture medium, but not in the presence of FBS. In this experiment, we investigated the effects of serum albumin on biocompatibility of HAm using alkaline phosphatase activity of osteoblastic MC3T3-E1 cells. HAm was pretreated with serum albumin in FBS-free medium at 37℃, and then it was washed with HEPES-buffered saline. The level of albumin, which was associated with HAm, increased according to increment of incubation time or albumin dose. The maximum level of albumin associated with HAm was approximately 47.6μg per mg HAm. The released level of albumin associated with HAm in the medium was less than 5% of the total albumin associated with HAm. HAm inhibited alkaline phosphatase activity of the cells, but the HAm-associated with albumin did not inhibit the enzyme activity at all. These results suggest that serum albumin may induce biocompatibility of HAm for osteoblastic cells.
