Multifunctional and Biocompatible Nanomaterials Based on Multiple Quantum Dots/Iron Oxide Nanoparticles-Embedded Silica Nanosphere

Abstract

Quantum dots (QDs) and superparamagnetic Fe3O4 nanoparticles (NPs) have garnered considerable attention in biomedical applications. Novel surface modification strategy could enhance the performance of those NPs. In chapter 1, silica-coated, QD–embedded silica NPs (QD-SiO2 NPs) containing QDs composed of CdSe@CdS@ZnS were prepared and the structure based advantages were compared with single QD having similar QY. These QD-SiO2 NPs exhibited ca. 200 times stronger photoluminescence (PL) than single QDs. Cytotoxicity studies revealed that QD-SiO2 NPs were less toxic than equivalent numbers of silica-free single QDs. The excellence of QD-SiO2 NPs with regard to in vitro applications was illustrated by significantly enhanced fluorescence signals from QD-SiO2 NPs internalized cancer cells and stem cells. In chapter 2, QD-assembled silica NPs bearing a polydiacetylene (PDA) supramolecules on their surface (PDA-QD-SiO2 NPs) were described. The resulting PDA-QD-SiO2 NPs showed discrete QD photoluminescence for encoding as well as PDA fluorescence for sensing a target without interference or overlap. Under heating stress of the PDA-QD-SiO2 NPs, the color of the PDA changed from blue to red, which also allowed us to observe the fluorescence emitted from red PDA. The mixture of two different PDA-QD-SiO2 NPs, bluePDA-QD-SiO2 NPs not emitting the fluorescence of PDA and redPDA-QD-SiO2 NPs on which stress was brought on to turn on the PDA fluorescence, was effectively imaged and readily distinguished via fluorescence microscopy, showing their potential for label-free and multiplexed detection of target molecules. In chapter 3, QDs-embedded silica NPs with an Fe3O4 NP core (M-QD-SiO2 NPs) that has dual functionalities were described. The M-QD-SiO2 NPs were mono-dispersed in size and exhibited super-paramagnetic and highly fluorescent properties. Most of the M-QD-SiO2 NPs were naturally internalized into MDA-MB-231 human breast cancer cells, and the NPs containing cells were successfully sorted by utilizing both fluorescence flow cytometry and a magnetic field. The results indicate that the M-QD-SiO2 NPs have great potential for multimodal cell separation. In chapter 4, double-layered Fe3O4 NPs containing silica nanoparticles (DL M-SiO2 NPs) were fabricated with a silica core and highly packed Fe3O4 NPs layers. The DL M-SiO2 NPs had a superparamagnetic property and efficient accumulation kinetics under an external magnetic field. Moreover, the magnetic field-exposed DL M-SiO2 NPs show quantitative accumulation, whereas single-layered Fe3O4 NPs containing silica nanoparticles (SL M-SiO2 NPs) and silica-coated Fe3O4 NPs produced a saturated plateau before full recovery of the NPs. DL M-SiO2 NPs are promising nanomaterials with a great potential to separate and analyze biomolecules.