In vitro osteogenetic activity of pearl.

In vivo and in vitro studies have shown that shell nacre and hydroxyapatite (HA) are promising bioactive materials for bone repair. In this work, the osteogenetic activity of pearl is evaluated by soaking it in simulated body fluid (SBF) and cell culture, taking shell nacre and HA as control materials at the same time. After soaking in SBF, HA particles were rapidly formed on the surface of pearl, the dissolution of CaCO3 and the binding between organic components and Ca2+ ions in pearl provide favorable conditions for the HA precipitation, and the whole process follows a dissolution-binding-precipitation mechanism. Calcium surplus, not conventional calcium deficiency, is found in HA crystal structure; it implies that type B-HA is formed on pearl surface in this study. HRTEM observation shows that HA is poorly crystallized with so many dislocations and shuttle-like amorphous areas. Cell culture reveals that pearl could stimulate osteoblast proliferation, which proceeded more quickly and smoothly than that on shell nacre and HA, and abundant extracellular matrix occupied the whole pearl surface by 5 days. It is concluded that pearl is a superior osteoinductive material with high osteogenetic activity.