Synthesis of Silica-Coated Magnetic Hydroxyapatite Composites for Drug Delivery Applications.

We have prepared a core-shell magnetic silica-coated hydroxyapatite, Fe₃O₄@SiO₂@HAp composite materials for pH-responsive drug delivery applications. Captopril (Cap) and ibuprofen (Ibu) were chosen as model hydrophilic and hydrophobic drugs, respectively. The drugs were encapsulated into the Fe₃O₄@SiO₂@HAp composite via electrostatic interactions with existing amine and carboxylic acid groups during calcium phosphate shell formation. The formation of calcium phosphate shell not only protects the encapsulated drugs from leaching but also controls the release rate of drugs from the composite system depending on various pH conditions. We have tested the release behavior of Cap and Ibu drugs under different pH conditions such as neutral pH (pH 7.4) and acidic pH (pH 5.0), respectively. The study result reveals that the synthesized Fe₃O₄@SiO₂@HAp composite is suitable for release of both water soluble and water insoluble drugs based on a pH-responsive controlled manner.