A combined experimental and molecular dynamics simulation study on doxorubicin adsorption on strontium-substituted hydroxyapatite hollow microspheres

Hydroxyapatite (HAp) materials with the functions of bone reconstruction as well as drug release have important applications in treatment of bone diseases. However, it still remains a challenge to synthesize ion-doped HAp with low crystallinity and high surface area to improve its biological responses and drug loading capacity. Herein, strontium-substituted hydroxyapatite (Sr-HAp) hollow microspheres that exhibit high drug loading efficiency and excellent biocompatibility are reported via a simple one-step hydrothermal method. The specific surface area of the as-prepared Sr-HAp microspheres can be as high as 214.69 m(2)/g. The simulation results show that there is no significant difference in the total binding energy between doxorubicin (DOX) and HAp as well as Sr-HAp. Both HAp and Sr-HAp show high DOX loading efficiency and sustained DOX release behavior. The binding between DOX and Sr-HAp is mainly through the electrostatic interaction between Ca or Sr ions on Sr-HAp surfaces and carbonyl-O or hydroxyl-O in DOX molecule. The findings provide insights into the design and development of drugs used in drug delivery system of HAp or ion-doped HAp materials.