Drug-loaded, magnetic, hollow silica nanocomposites for nanomedicine

Magnetic, hollow silica nanocomposites (MHSNC), including nanospheres and nanotubes, have been successfully synthesized using a coating of Fe3O4 magnetic nanoparticles (NPs) (similar to 10 nm) and silica on nanosized spherical and nanoneedle-like calcium carbonate (CaCO3) surfaces under alkaline conditions. The nanosized CaCO3 surfaces were used as nanotemplates, and tetraethoxysilane and magnetic NPs were used as precursors. The as-synthesized MHSNC were immersed in an acidic solution to remove the CaCO3, forming magnetic, hollow silica nanospheres and nanotubes. The MHSNC were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray powder diffraction, and superconducting quantum interference device (SQUID) magnetometer. SEM and TEM results showed that a smooth surface of MHSNC and a thin layer of silica (similar to 10 nm) embedded with the magnetic NPs were successfully formed, and that the CaCO3 nanotemplates appeared to be dissolved. SQUID measurement demonstrated that magnetization of MHSNC was dependent on temperature, exhibiting superparamagnetism. The MHSNC were immersed in ibuprofen solution. The amount of the loaded drug was determined to be 12 wt% for nanospheres, and 8 wt% for nanotubes by UV measurement, respectively. Drug-loaded MHSNC have potential applications in nanomedicine. (C) 2005 Elsevier Inc. All rights reserved.