(354c) Bifunctional Quantum Dot-Iron Oxide Nanoparticle Composites

Deng, S., Chinese Research Academy of Environmental Science

Since their introduction, nanoparticles have made significant contributions to the field of biological imaging. However, nanoparticles also have interesting electromagnetic properties that may be exploited to directly manipulate cells. Nanocomposite materials containing both functionalities will provide enhanced functionality in contrast with their more limited single-component counterparts. We are investigating one class of nanocomposites, fluorescent-magnetic particles, which may allow for direct mechanical manipulation and simultaneous observation of subcellular features. These composites are composed of iron oxide and quantum dot materials. Quantum dots have been extensively studied for their unique optical and electronic prosperities, sharp emission band with broad excitation, and strong resistance to photobleaching. They are of great interest for their dimensional similarities to biomarcromolecules (e. g., DNA and protein), applications in biological imaging, and bioconjugation. Superparamagnetic iron oxide nanoparticles (SPIONs) have also been studied for biomedical applications, including MRI contrast enhancement, magnetic immobilization, and drug targeting. Here, we present synthesis and characterization of a new bifunctional nanocomposite: CdTe-Fe3O4@SiO2. CdTe is an ideal imaging material as the emission can be tuned to the near infrared where optical tissue absorption is at a minimum, whereas the silica shell can prevent the photooxidation and subsequent elution of toxic Cd2+ and biodegradation of iron oxide magnetic nanoparticles. Additionally, silica surfaces provide a mechanism for facile conjugation to targeting biomolecules (e.g., proteins). To create these composites, a two-step synthesis was employed. First, CdTe QDs were conjugated to magnetic Fe3O4 nanoparticles using a one-pot chemical method. Second, CdTe-Fe3O4 conjugates were modified with an outer silica shell. Particles were characterized using TEM, XRD, UV and fluorescence spectroscopy, and superconducting quantum interference device (SQUID). Result indicated that nanocomposites exhibit magnetic properties and fluorescence. These nanocomposites have potential in combined MRI/fluorescence imaging, diagnostics, circulating drug-delivery systems, and investigation of mechanotransduction in biological systems.