Dynamics and mechanisms of quantum dot nanoparticle cellular uptake

Abstract

BackgroundThe rapid growth of the nanotechnology industry and the wide application of various nanomaterials have raised concerns over their impact on the environment and human health. Yet little is known about the mechanism of cellular uptake and cytotoxicity of nanoparticles. An array of nanomaterials has recently been introduced into cancer research promising for remarkable improvements in diagnosis and treatment of the disease. Among them, quantum dots (QDs) distinguish themselves in offering many intrinsic photophysical properties that are desirable for targeted imaging and drug delivery.ResultsWe explored the kinetics and mechanism of cellular uptake of QDs with different surface coatings in two human mammary cells. Using fluorescence microscopy and laser scanning cytometry (LSC), we found that both MCF-7 and MCF-10A cells internalized large amount of QD655-COOH, but the percentage of endocytosing cells is slightly higher in MCF-7 cell line than in MCF-10A cell line. Live cell fluorescent imaging showed that QD cellular uptake increases with time over 40 h of incubation. Staining cells with dyes specific to various intracellular organelles indicated that QDs were localized in lysosomes. Transmission electron microscopy (TEM) images suggested a potential pathway for QD cellular uptake mechanism involving three major stages: endocytosis, sequestration in early endosomes, and translocation to later endosomes or lysosomes. No cytotoxicity was observed in cells incubated with 0.8 nM of QDs for a period of 72 h.ConclusionsThe findings presented here provide information on the mechanism of QD endocytosis that could be exploited to reduce non-specific targeting, thereby improving specific targeting of QDs in cancer diagnosis and treatment applications. These findings are also important in understanding the cytotoxicity of nanomaterials and in emphasizing the importance of strict environmental control of nanoparticles.

Intracellular distribution of nontargeted quantum dots after natural uptake and microinjection

“…It should be noted that phases 1 and 2 of quantum dot distribution in the cells were found earlier in the studies reported by Hoshino et al, 16 Clift et al, 20 and Jiang et al, 19 Kelf et al, 14 Williams et al, 15 and Corsi et al, 17 which showed formation of vesicular structures spread in the cytoplasm corresponding to phase 2. Phase 3, ie, localization of vesicular structures in the perinuclear region, was described by Zhang et al 22 and Xiao et al, 23 and reviewed by Parak et al 33 Phase 4 resembles the data on formation of multivesicular body-like structures and their redistribution in cytoplasm presented by Yuan et al 18 and Jiang et al 19 However, there has been no presentation of an overall picture illustrating the time-dependent nature of natural uptake and distribution of nontargeted negatively charged quantum dots in living cells.…”

“…1,11,12 Analysis of results presented in the literature reveals a very wide range of values for quantum dot internalization parameters, in particular, uptake time and intracellular localization. [13][14][15][16][17][18][19][20][21][22][23][24] This could be due to time-dependent changes in accumulation and intracellular distribution of quantum dots taking place even in a single cell line. The interpretation of results is even more complicated in the case of in vivo studies where the quantum dots would be internalized by different types of cells.…”

Short Ligands Affect Modes of QD Uptake and Elimination in Human Cells

“…Neutral or negatively charged QDs are only weakly bound to the lipid bilayer and thus are less readily taken up. 25 Given their size (4À5 nm in radius), QDs cross the plasma membrane primarily through pinocytosis, a distinct set of endocytosis mechanisms, chiefly responsible for the uptake of cell nutrients and other small particles (<100 nm). The contribution of each endocytosis pathway can be assessed using inhibitors that suppress specific internalization processes.…”

Entrapment in phospholipid vesicles quenches photoactivity of quantum dots

“…However, differently from the liposomes that irreversibly leaked ( It must be noted that nonspecific passive delivery of QDs, though noninvasive and supposedly not compromising cell integrity and viability, completely relies on endocytosis. 61,62 However, similar QDs from clathrin-coated pits can be destined for different fates after internalization: sent back to the cell surface, trafficked toward a degradative fate in endosomes and lysosomes, or to the perinuclear recycling endosomal compartment, depending on cell phenotype. 63 This means that internalization and trafficking of QDs, though highly controlled by the cell, can be manipulated by choosing proper targeting ligands.…”