Endo- and Exocytosis of Zwitterionic Quantum Dot Nanoparticles by Live HeLa Cells

• Published in: ACS nano 2010-11, Vol.4 (11), p.6787-6797
• Main Authors: Jiang, Xiue, Röcker, Carlheinz, Hafner, Margit, Brandholt, Stefan, Dörlich, René M, Nienhaus, G. Ulrich
• Format: Article
• Language: English
• Subjects: Buffers; Cell Membrane - metabolism; Cell Survival; Endocytosis; Exocytosis; HeLa Cells; Humans; Kinetics; Microscopy, Confocal; Penicillamine - chemistry; Penicillamine - metabolism; Quantum Dots
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/nn101277w

Uptake and intracellular transport of D-penicillamine coated quantum dots (DPA-QDs) of 4 nm radius by live HeLa cells have been investigated systematically by spinning disk and 4Pi confocal microscopies. Unlike larger nanoparticles, these small DPA-QDs were observed to accumulate at the plasma membrane prior to internalization, and the uptake efficiency scaled nonlinearly with the nanoparticle concentration. Both observations indicate that a critical threshold density has to be exceeded for triggering the internalization process. By using specific inhibitors, we showed that DPA-QDs were predominantly internalized by clathrin-mediated endocytosis and to a smaller extent by macropinocytosis. Clusters of DPA-QDs were found in endosomes, which were actively transported along microtubules toward the perinuclear region. Later on, a significant fraction of endocytosed DPA-QDs were found in lysosomes, while others were actively transported to the cell periphery and exocytosed with a half-life of 21 min.