Synthesis of magnetic and fluorescent multifunctional hollow silica nanocomposites for live cell imaging.

In this paper, we report a synthesis of multifunctional core/shell silica nanocomposites in mixed water-ethanol solvents at room temperature. Water-soluble CTAB-stabilized nanoparticles (Fe(3)O(4) and quantum dots) are used as templates and tetraethoxysilane (TEOS) is used as a precursor to fabricate multifunctional hollow silica nanocomposites. Owing to the high abundance of folate receptors in many cancer cells, folic acid is used as the targeting ligand. By coupling with folic acids, the multifunctional silica nanocomposites conjugates are successfully used for tumor cell imaging. In vitro cellular uptakes of such SiO(2) nanocomposites are investigated with fluorescence microscope, which demonstrate much higher internalization of the folate-decorated SiO(2) nanocomposites by Hela cancer cells which are of over-expression of folate receptors than the cellular uptake by NIH 3T3 fibroblast cells which are of low expression of folate receptors. Magnetic manipulation, fluorescence imaging, hollow structure, and cell targeting are simultaneously possible using a multifunctional silica nanocomposite. Our results demonstrate a robust hydrophobic nanoparticles-based approach for preparing multifunctional and biocompatible hollow silica composites, which could be also suitable for silica coating of other kinds of nanoparticles. Copyright 2010 Elsevier Inc. All rights reserved.