Surface properties of quantum dots define their cellular endocytic routes, mitogenic stimulation and suppression of cell migration.

Abstract

The practical use of quantum dots (QD) as diagnostic, visualizing and therapeutic nano-agents depends on the understanding of fundamental mechanisms of their entrance and trafficking within cells. Here we show that CdSe/ZnS carboxylic-coated QD (COOH-QD) enter fibroblast cells via lipid raft/caveolin-mediated endocytosis, pass early sorting endosomes and accumulate in the multivesicular bodies, but not in the lysosomes. Later phase of their endocytosis leads to the generation of lipid raft/caveolin-dependent endocytosis inhibition that prevents intracellular uptake of new COOH-QD, but not the QD coupled with platelet-derived growth factor BB (PDGF-QD). PDGF-QD enter fibroblasts by the clathrin-mediated endocytosis and undergo similar intracellular trafficking as COOH-QD, yet they accumulate in lysosomes in contrast to COOH-QD. The PDGF-QD activate PDGF receptor-beta and are mitogenic, however, COOH-QD suppress cell migration and chemotaxis. Data show that surface coating of QD with the biologically active proteins redirects their intracellular traffic routes and changes their biological activity.