The applications of nanoparticles based on semiconductors, iron oxides or other materials in biology and medicine have been extensively demonstrated. Herein we describe our efforts to synthesize nanomaterials combining two or more types of the above-mentioned materials, and to apply these nanocomposites for biological uses. Hybrid materials of fluorescent quantum dots and superparamagnetic iron oxide nanoparticles have been prepared by procedures of sequential crystal growth and physical encapsulation. An interesting finding is that the fluorescent and magnetic properties of the composite products are dependent upon the preparation procedures used. In addition to these fluorescent-magnetic nanoparticles, we have also explored the incorporation of other functionalities such as controlled release and enhanced cellular delivery.

The biocompatibility of our products has been confirmed in cellular studies. We are currently actively pursuing the use of the nanocomposites in basic biomedical research and clinical diagnosis, imaging and therapy. For example, combining the superparamagnetism of iron oxide nanoparticles and the bright fluorescence of semiconductor nanocrystals makes it possible to mechanically manipulate cells with the manipulation effect monitored in real time. Furthermore, encapsulating drugs along with magnetic and fluorescent nanoparticles into a polymer/lipid matrix could provide a 4-stage nanotechnology cancer treatment: the polymer/lipid nanoparticles find the tumor by active or passive targeting; magnetic nanoparticle-mediated MRI imaging locates the tumor deep in human body; fluorescent nanoparticles guide the physician to surgically remove the majority of tumor tissue; and finally the sustained release of anticancer drugs from the polymer/lipid matrix kills the remaining cancer cells.