Research on the adsorption and release behavior of lysozyme on hollow multilayer hydroxyapatite microspheres

Hollow hydroxyapatite microspheres,consisting of a hollow core and a multilayer porous shell,were prepared by converting Li2O-CaO-B2O3 glass microspheres in dilute phosphate solution.Lysozyme was used as the drug model of proteins,then the adsorption and in vitro drug release behaviors were studied.It was found that the adsorption mechanism was different with various concentration of lysozyme solution.When the concentration was lower than 0.8mg/mL,the adsorption was occurred on the surface of microspheres,the adsorption behavior was in accordance with the Langmuir adsorption model.In vitro release showed lysozyme was released completely in 48h.When the concentration was higher than 0.8mg/mL,more adsorption of lysozyme was occurred on the inner shell of the microsphere,the adsorption behavior was in accordance with the Henry adsorption model.And the release of lysozyme from the hollow HA microspheres could be lasted an extended period(up to 800h).The present delivery system established could be used as the controlled drug release carrier for proteins,such as growth factor.