Preparation of HAp whiskers with or without Mg ions and their effects on the mechanical properties and osteogenic activity of poly(D,L-lactide)

Hydroxyapatite whiskers (HAp-Ws) and magnesium-substituted hydroxyapatite whiskers (Mg-HAp-Ws) with 1, 3, and 5 mol% magnesium (Mg) ion substitution contents were successfully prepared by the hydrothermal method. The incorporation of Mg ion into the HAp-Ws led to a morphology including a combination of whiskers and particles and a decrease in the crystal interplanar spacing. Then, the HAp-Ws and Mg-HAp-Ws were further introduced into a poly(D,L-lactide) (PDLLA) matrix to prepare HAp-Ws/PDLLA and Mg-HAp-Ws/PDLLA composite films. The existence of HAp-Ws or Mg-HAp-Ws can endow composite films with superior hydrophilicity and tensile properties. Moreover, since the HAp-Ws have a good morphology and a large aspect ratio, the tensile strength and modulus of the HAp-Ws/PDLLA composite film were reasonably higher than those of the Mg-HApWs/PDLLA composite film. The Mg-HAp-Ws/PDLLA composite films were more beneficial for MC3T3-E1 cell adhesion, proliferation and differentiation due to the presence of Mg ions. More importantly, the osteogenic effect of Mg ions on MC3T3-E1 cells is dose-dependent, and the Mg-HAp-Ws/PDLLA composite films with 1-3 mol% Mg ion contents in the Mg-HAp-Ws showed relatively good cytocompatibility and osteogenic activity. In short, the mechanical properties and osteogenic activity of Mg-HAp-Ws/PDLLA composite films can be regulated by adjusting the Mg/Ca content to better meet the needs of bone repair.