Size-Selective active Compartmentalisation of Quantum Dots in Living Human Phagocytic Cells

Abstract: The advent of nanotechnology progressively increases human cell and tissue exposure to ultra-fine objects encountered in environmental, industrial and biomedical settings. A unique opportunity to investigate and directly monitor intricate consequences of such encounters in living cells is offered by semiconductor quantum dots (QDs) rapidly surpassing traditional organic dyes as superior fluorescent probes. We demonstrate specific rapid intracellular localisation of extremely small highly luminescent water-soluble CdTe QDs6 in human monocyte-derived macrophages that is size specific on the nanometer scale. CdTe QDs of 2 nm mean size emitting green at 515nm display a nuclear location while those QDs with a 3.3nm mean size and emitting red at 617nm exhibit a cytoplasmic compartmentalisation. The smaller green CdTe QDs undergo active transport to the nucleus where they accumulate at the nucleolus. Taken together, our data demonstrate that biocompatible CdTe QDs display hallmarks of material with outstanding potential for use in biomedical research, therapeutics and imaging of intracellular dynamics at the subcellular level. These findings are also important in the context that environmental nanoparticles would be expected to present to the human body at epithelial surfaces in skin and bronchial epithelium, which emphasizes the importance of strict enviromental control of nanoparticles.