Self-oriented hydroxyapatite nanorods in gelatin matrix via single- directional evaporation for bone defect repair

Bone, as a typical anisotropic material, with hydroxyapatite nanocrystals oriented in the direction of collagen fibrils. Drawing inspiration from nature, constructing bone defect repair scaffolds by mimicking the natural components and structures of bones to recreate the microenvironment at the bone defect site is an effective strategy. However, it is quite challenging to precisely control the orientation behavior of nanoscale hydroxyapatite nanorods. Here, for the first time, by adjusting the aspect ratio of HAP and the size of the hydrogel grid, the preferential orientation of HAP can be achieved through the directional evaporation of water in the hydrogel. And we introduced Fe ²⁺ into the hydroxyapatite lattice, while maintaining the original rod-like morphology of HAP without introducing the magnetic mineral impurity phase. Animal experiments indicated that the anisotropic gelatin/hydroxyapatite scaffolds can effectively accelerate the repair process of large-sized bone defects.