Synthesis of Magnetic Nanoparticle Cluster-Quantum Dot Composites and Application for Fluorescent Barcoding Nanomaterials

Abstract

Magnetic nanoparticle have been intensively investigated for in vitro and in vivo applications such as a contrast agent for magnetic resonance imaging and magnetically guided drug delivery vehicles due to their magnetic properties, biocompatibility. Magnetic nanoparticle clusters (MNCs) have strong paramagnetic properties and they can be easily separated by using hand-held magnet. To achieve bio-separation of multiple compounds simultaneously, selective detection ability of MNCs is necessary. Quantum dots (QDs) are one of the promising materials for spectroscopic barcoding materials. By changing their size, emission wavelength of QDs could be controlled. In addition, QDs have narrow emission spectrum. For these reasons, QDs are favored for displaying signal of optical barcodes. Here, MNCs and QDs were combined to synthesize fluorescent barcoding nanomaterials with magnetic properties. Firstly, the surface of MNCs and QDs were encapsulated by amphiphilic polyethylene imine (amPEI) for dispersion in water and then, QD-amPEI was mixed with MNC-amPEI to form MNC-QD-amPEI. To improve the structural and optical stability, MNC-QD-amPEI was coated with silica to form MNC-QD-amPEI-SiO2 composite. The composites showed stable fluorescence intensity for more than two weeks and most of the composites moved along external magnetic force. For barcoding nanomaterials, different ratio of red and green emitting QDs were used in the synthesizing process. By controlling the ratio of the QDs, four different colored fluorescent barcoding composites were synthesized and their optical and magnetic properties were confirmed by fluorescence microscope. Stable and optically distinguishable MNC-QD-amPEI-SiO2 composites have a potential candidate for bio-separation of multiple chemical compounds.