Synthesis and Investigation of the Properties of Water Soluble Quantum Dots for Bioapplications

Abstract

Semiconductor nanocrystals or quantum dots (QDs) have received a great deal of attention over the last decade due to their unique optical and physical properties, classifying them as potential tools for biological and medical applications. However, there are some serious restrictions to the bioapplications of QDs such as water solubility, toxicity and photostability in biological environments for both in-vivo and in- vitro studies. In this thesis, studies have focused on the preparation of highly luminescent, water soluble and photostable QDs of low toxicity that can then be potentially used in a biological context. First, CdSe nanoparticles were synthesized in an aqueous route in order to investigate the parameters affecting formation of nanoparticles. Then, water soluble CdSe(S) and ZnSe(S) QDs were synthesized. These CdSe(S) QDs were also coated with ZnO and Fe2O3 to produce CdSe(S)/ZnO and CdSe(S)/Fe2O3 core/shell QDs. The cytotoxicity of as-prepared CdSe(S), ZnSe (S) and CdSe(S)/ZnO QDs was studied in the presence of two cell lines: HCT-116 cell line as cancer cells and WS1 cell line as normal cells. Finally, CdSe(S) QDs were linked to Donkey-anti mouse (H+L) (IgG) antibody Cy3 fluorophore to prepare a CdSe(S)-antibody conjugated compound and the photostability of CdSe(S) QDs both after linking to antibody and in the presence of HCT-116 cells was investigated. The obtained QDs exhibited high crystallinity, water solubility, low toxicity and photostability, demonstrating that highly crystalline nanoparticles can be formed by sufficient control of the experimental parameters. It was determined that coating the CdSe(S) QDs with ZnO led to a reduced cytotoxicity of the CdSe(S) QDs. It was found that ZnSe(S) QDs have no cytotoxicity toward both HCT-116 and WS1 cell lines across all concentrations studied. Finally, the CdSe(S) QDs were found to be photostable both in a CdSe(S)-antibody conjugated compound and in the presence of HCT-116 cancer cells.