QUANTUM DOT SINGLE MOLECULE TRACKING REVEALS A WIDE RANGE OF DIFFUSIVE MOTIONS OF MEMBRANE TRANSPORT PROTEINS

Visualizing Subcellular Localization of a Protein in the Heart using Quantum Dots-Mediated Immuno-Labeling followed by Transmission Electron Microscopy

The subcellular localization is critical to delineating proper function and determining the molecular mechanisms of a particular protein. Several qualitative and quantitative techniques are used to determine the subcellular localization of proteins. One of the emerging techniques in determining the subcellular localization of a protein is quantum dots (QD)-mediated immunolabeling of a protein followed by imaging them with transmission electron microscopy (TEM). QD is a semiconductor nanocrystal with a dual property of crystalline structure and high electron density, which makes them applicable to electron microscopy. This current method visualized the subcellular localization of Sigma 1 receptor (Sigmar1) protein using QD-TEM in the heart tissue at ultrastructural level. Small cubes of the heart tissue sections from a wild-type mouse were fixed in 3% glutaraldehyde, subsequently osmicated, stained with uranyl acetate, followed by sequential dehydration with ethanol and acetone. These dehydrated heart tissue sections were embedded in low-viscosity epoxy resins, cut into thin sections of 500 nm thickness, put on the grid, and subsequently subjected to antigen unmasking with 5% sodium metaperiodate, followed by quenching of the residual aldehydes with glycine. The tissues were blocked, followed by sequential incubation in primary antibody, biotinylated secondary antibody, and streptavidin-conjugated QD. These stained sections were blot dried and imaged at high magnification using TEM. The QD-TEM technique allowed the visualization of Sigmar1 protein's subcellular localization at the ultrastructural level in the heart. These techniques can be used to visualize the presence of any protein and subcellular localization in any organ system.

Characteristics of quantum dots phagocytosis by neutrophil granulocytes

This article describes the main morphological and biochemical features of neutrophil granulocytes in the process of phagocytosis of two types of quantum dots (CdSe/ZnS-MPA and CdSe/CdSeZnS/ZnS-PTVP). This study is the first to observe the transfer of large aggregates of quantum dots through neutrophils. During this process the cells demonstrate high chemotactic activity. Furthermore, neutrophil pseudopodia underwent alterations during the early stages of phagocytosis. The findings demonstrated that the biochemical profile of neutrophils is practically identical after phagocytosis of both types of quantum dots, but differs significantly from neutrophil metabolism after bacterial phagocytosis.

Using of Quantum Dots in Biology and Medicine

Quantum dots are nanoparticles, which due to their unique physical and chemical (first of all optical) properties, are promising in biology and medicine. There are many ways for quantum dots synthesis, both in the form of nanoislands self-forming on the surfaces, which can be used as single-photon emitters in electronics for storing information, and in the form of colloidal quantum dots for diagnostic and therapeutic purposes in living systems. The paper describes the main methods of quantum dots synthesis and summarizes medical and biological ways of their use. The main emphasis is laid on the ways of quantum dots surface modification. Influence of the size and form of nanoparticles, charge on the surfaces of quantum dots, and cover type on the efficiency of internalization by cells and cell compartments is shown. The main mechanisms of penetration are considered.