Highly fluorescent positively charged ZnSe quantum dots for bioimaging

Quantum Dots (QDs) are fluorescent semiconductor nanocrystals with unique optical properties, which are being highly applied in opto-electronic devices and biological sciences. Aiming at biological applications we developed highly blue fluorescent Cysteamine coated ZnSe QDs. They were prepared in aqueous medium at near physiological pH by a fast precipitation process followed by hydrothermal growth. The characteristic excitonic emission output was enhanced by decreasing their surface defects via an UV photoactivation procedure. We tested their in vitro cytotoxicity towards macrophage cells and probed their functionality by labeling two different cell types: Candida albicans and red blood cells by electrostatic interaction with the negative cell membranes. The overall results show that these positively charged QDs can be applied as new low toxic and promising platforms for biolabeling purposes.