Effects of drying methods on the preparation of dexamethasone-loaded chitosan microspheres

The purpose of this study was to investigate the effects of drying methods on the preparation of dexamethasone- (Dex-) loaded chitosan microspheres. Two drying methods, namely, air drying and freeze drying, were adopted. The physical properties of the beads were first investigated and then the loading and release of Dex were characterized. Finally, the bioactivity of released Dex was evaluated. The data showed that, compared with freeze-dried beads, air-dried beads were denser and smaller, and had lower swelling ratios, slower degradation rate and greater Rockwell hardness. In terms of drug delivery, air-dried beads had lower encapsulation efficiency and a slower release rate of Dex. Regarding bioactivity, both groups prompted cell differentiation without significant differences. However, Dex released from freeze-dried beads inhibited cell proliferation, while Dex released from air-dried beads did not. Based on these results, we conclude that incorporation of Dex enhanced the osteogenic potential of chitosan microspheres and drying methods did affect the physical properties of the chitosan microspheres, which further influenced the drug loading and release. At the moment, the air-drying method is more appropriate to prepare Dex-loaded chitosan microspheres.