Preparation of pore expanded mesoporous hydroxyapatite via auxiliary solubilizing template method

•CTAB and TMB were used as soft template and pore expanding agent, respectively.•Average length of the as-synthesized HAp nanoparticles is 50–150nm.•Large amount of mesoporous spread around the surface of mesoHAp nanorods.•The shape of mesopores was elongated and opened at both extremities.•Pore diameter of mesoHAp was up to 15nm, indicating the pore enlargement of TMB. Here we present a facile approach to prepare pore-expanding mesoporous hydroxyapatite (mesoHAp) using solubilized micelle template. 1,3,5-rimethy benzene (TMB) was selected as auxiliary solubilizer together with the general soft template cetyltrimethylammonium bromide (CTAB). Enlarged mesoporous can be obtained through the swelling of micelle. Numerous individual nano channels can be observed under TEM images spreading and penetrating within the mesoHAp nanorods. Compared to the mesoHAp without TMB, the channels have enlarged dimensions of about 5–15nm and the space between the nano channels are filled with an ordered crystalline HAp structure with typical hexagonal crystals. A probable mechanism is that TMB can enter into the amphiphilic CTAB micelle to form swelled TMB/CTAB-PO43− complex, and in the presence of Ca2+, Ca9(PO4)6 clusters are preferentially condensed on the micelle surface due to the conformation compatibility between the identical hexagonal shapes of the micelles and Ca9(PO4)6. Interesting, the pore size distribution of mesoHAp was centered at ∼4.7nm and ∼10nm, which might be arisen from the coexistence of both unsolubilized CTAB micelles and solubilized TMB/CTAB micelles. The pore-enlarged mesoHAp nanoparticles presented a platform for protein delivery system and might be applicable in biocomposite scaffold for bone regeneration.