Aqueous phase synthesis and functionalization of semiconductor quantum dots for biomedical applications

In this thesis, efforts have been made to investigate and optimize the aqueous synthesis route in order to prepare high quality QDs. Reaction for high quality CdTe QD preparation was firstly investigated. It was found that, species and concentration of surfactants are important factors which greatly influence the growth dynamics, optical properties and stability of the QDs. A mix-ligands system composed of mercaptopropionic acid (MPA) and Cysteine (Cys) was then optimized to generate high quality CdTe QDs. To avoid the heavy metal related toxicity issues, high quality Mn-doped ZnSe QDs (d-dots) were synthesized as an alternative to Cd-based QDs. The d-dots are characterized with large Stokes shift and long PL lifetime, and found to be biocompatible for biological applications. A sandwiched core/shell QD (SQD, Mn:ZnSe/ZnS/ZnMnS) was also formulated as high quality contrast agent for both optical fluorescence imaging and magnetic resonance imaging (MRI). After proper surface modification and bio-functionalziation, the d-dots were developed as theranostic agents for in vitro cancer diagnosis and therapy. Two types of nanocarriers, namely d-dot/polymer nanoplex and d-dot/liposome hybrid, were developed as optically traceable nanocarrier for cancer cell targeted gene delivery. The therapeutic effect was confirmed by the significantly suppressed expression of the targeted gene sequence (mutant K-Ras) at mRNA level. The SQD/liposome hybrid was also developed as a multifunctional platform for MR/optical dual mode imaging and gene/drug co-delivery.DOCTOR OF PHILOSOPHY (EEE