CDTE quantum dots – preparation, physico-chemical properties and application as fluorescent markers

A set of water-soluble CdTe quantum dots (QDs) was prepared by the chemical reaction between cadmium chloride and sodium hydrogen telluride in the presence of 3-mercaptopropionic acid (MPA). QDs were characterized using fluorescence spectroscopy, lifetime measurements, slab-gel and capillary electrophoresis. The particle sizes, determining the wavelength of the fluorescence emission, were evaluated to be from 2.5 nm (500 nm) to 5.2 nm (750 nm). The fluorescence lifetimes determined by the time-resolved fluorescence spectrometry, increases from 3.05 to 20.5 ns with the increasing size of particles. The uptake of non-conjugated QDs into the living cells, which has a potential for single cell analyses, was apparent for human lymphocytes and yeast cells (Saccharomyces cerevisiae) after 30 minutes and 3 hours, respectively. The cell manipulation, lysis and monitoring was performed in microfluidic devices with laser-induced fluorescence detection. The conjugation of QDs with functional biomolecules allows the selective labeling and localization of specific molecules. Several coupling agents such as N-hydroxysulfosuccinimide (NHS) and 1-ethyl-3-(3- dimethylaminopropyl)carbodiimide hydrochloride (EDC) or carbonyldiimidazole (CDI) were used. The concentrations of reaction products were checked by capillary electrophoresis with laser-induced fluorescence detection