Extracellular Vesicles: Nature’s Own Nanoparticles

Abstract

Biological systems often feature natural, functional nanomaterials, including hemoglobin’s (6.5 nm), antibodies (12 nm), viruses (such as parvoviruses (18–26 nm), rhinovirus (30 nm)), hepatitis (45 nm) and bacteria (such as Pelagibacter Ubique (0.37–0.89 µm)). These natural nanoscale materials and organisms have not only inspired the design of some nanomaterials but also promoted the research on the world of nanotechnology. During this article we will introduce interesting biological sphered nano-sized liposomes called extracellular vesicles. About 40 years ago, it was discovered that all cells release diverse types of membrane vesicles into the extracellular environment. Initially, it was thought that extracellular vesicles were simply artefacts or trash compartments discarded by cells. It is now known that they play a vital role in cell function and cell-to-cell or cell-to-host communication, immune signaling, differentiation, and have applications in the detection of many human diseases such as cancer, AIDS, neurodegenerative disorders and in the synthesis of some vaccines. Since their discovery, extracellular vesicles are attracting considerable interest in the scientific community. Hence, many diverse names have been used to refer to these vesicles including ectosomes, microparticles, microvesicles but the more general term used is extracellular vesicles. Mammalian extracellular vesicles can be classified into exosomes, microvesicles and apoptotic bodies depending on their size and biogenesis. On the other hand, bacterial extracellular vesicles are less studied compared to the mammalian extracellular vesicles. In Gram-negative bacteria, they are referred to as outer-membrane vesicles since they are produced by the pinching off the outer membrane. However, in Gram-positive bacteria, despite the fact that they lack an outer membrane, it was proven that they also produce vesicles which are referred to as membrane vesicles. During this article we will focus on the biogenesis, role and applications of mammalian and bacterial derived extracellular vesicles. Also, particular focus on the methods of isolation and subsequent characterization methods will be reviewed.