Bilayer-Embedded Lipid Droplets Coated with Perilipin-2 Display a Pancake Shape.

Lipid droplets (LD) are organelles localized in the membrane of the endoplasmic reticulum (ER) that play an important role in many biological functions. Free LDs that have been released from the ER membrane and are present in the cytosol resemble an oil-in-water emulsion. The surface of an LD is coated with a phospholipid monolayer, and the core of an LD is composed of neutral lipids. Adipose differentiation-related protein (ADRP), also known as perilipin-2, is a protein that surrounds the LD, together with the phospholipid monolayer. ADRP molecules are involved in assisting in the storage of neutral lipids within LDs. In this article, we focus our interest on the influence of ADRP molecules on the 3D shape of bilayer-embedded LDs and the diffusion of phospholipids in the monolayer covering LDs. For this study, we employed two different microfluidic setups: one to produce and explore bilayer-embedded LDs and a second one to mimic the surface of a single LD. Using the first setup, we demonstrate that ADRP molecules stay preferentially localized on the surfaces of bilayer-embedded LDs, and we study their 3D-shape in the presence of ADRP. Using the second setup, we performed FRAP experiments to measure the phospholipid diffusion on a model LD surface as a function of the ADRP concentration. Although the presence of proteins on the LD surface minimally affects the phospholipid and protein motility, ADRP appears to have a significant effect on the 3D structure of LDs embedded in the bilayer.

Phospholipids diffusion on the surface of model lipid droplets.

Lipid droplets (LD) are organelles localized in the membrane of the Endoplasmic Reticulum (ER) that play an important role in metabolic functions. They consist of a core of neutral lipids surrounded by a monolayer of phosphoplipids and proteins resembling an oil-in-water emulsion droplet. Many studies have focused on the biophysical properties of these LDs. However, despite numerous efforts, we are lacking information on the mobility of phospholipids on the LDs surface, although they may play a key role in the protein distribution. In this article, we developed a microfluidic setup that allows the formation of a triolein-buffer interface decorated with a phospholipid monolayer. Using this setup, we measured the motility of phospholipid molecules by performing Fluorescent Recovery After Photobleaching (FRAP) experiments for different lipidic compositions. The results of the FRAP measurements reveal that the motility of phospholipids is controlled by the monolayer packing decorating the interface.

Antibody-modified magnetic nanoparticles as specific high-efficient cell-separation agents.

Separation of tumor cells is a promising approach that helps not only in early detection of cancer but also as an efficient tool that holds great importance in prohibiting cancer cell mutation, drug resistance to treatments, and in granting successful adjuvant therapies. As one of the highly efficient processes for the separation of single cells, tumor cells, and specific proteins from fresh whole blood, a magnetic iron oxide nanoparticle (IONP)-based immunomagnetic separation technique has been developed in this article. The synthesized IONPs were modified with antibodies (Abs) against human epithelial growth factor receptor 2 (HER2), which is overexpressed and/or amplified in about 15% of breast cancer patients with several types of human cancer cells. The prepared Ab-conjugated IONPs (Ab-IONPs) attach HER2-positive cancer cells exclusively and can serve as specific high-efficient single-cell separation agents. The results showed that the magnetic IONPs have been successfully attached to the Abs via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide linkers. Maximum targeting efficiency of the Ab-IONP complex, which was 94.5 ± 0.8% for BT474 and 70.6 ± 0.4% for mixture of cells (BT474 and MCF7), was achieved with a minimum amount of Abs, to provide an economically efficient single-cell detection device.