Counting and Sizing of Single Vesicles/Liposomes by Electrochemical Events

Abstract

The analysis of single entities in a liquid phase by electrochemical events has received much attention in recent years due to innovations and advances in exciting electrochemical methods as well as precise manufacturing techniques. Vesicles, as a special type of entity, play an important role in biological systems. However, the soft character and complex surface chemistry of vesicles present inherent challenges for single‐vesicle analysis. This minireview mainly focuses on the theory and recent progress of single‐vesicle/liposome analysis based on electrochemical events. Three different analytical principles, namely, pore/channel translocation, microelectrode impact and nanopipette collision, are reviewed and expatiated. Not only the capabilities for size determination, vesicle/liposome counting and the electroactive quantification of the contents within vesicles/liposomes but also the specificities of vesicle/liposome or entity‐pore/electrode interactions reflected in translocation or collision events are discussed in detail. Moreover, the advantages and disadvantages of each method of single‐vesicle analysis are discussed in this minireview.

Lipid Membrane Permeability of Synthetic Redox DMPC Liposomes Investigated by Single Electrochemical Collisions

“…[35][36][37][38][39][40][41] Especially, the electrochemical detection of single liposome collisions at UMEs is becoming an efficient and complementary tool for analyzing fundamental biological processes related to intracellular and extracellular electron transfers to discrete biological or artificial entities. [42][43][44] To explore the factors influencing the vesicles membrane permeability, we investigated the electrochemical and electrocatalytic reaction of different aqueous redox species (potassium ferrocyanide and cobalt(II) nitrate) encapsulated inside synthetic DMPC (1,2dimyristoyl-sn-glycero-3-phosphocholine) liposomes subjected to different experimental conditions (addition of surfactant, increase of temperature or presence of a redox probe in solution), by single collision detection on 10 μm diameter UMEs (Pt and carbon) as illustrated in Figure 1. We discuss the effect of the solution temperature on the liposome collision, its membrane rupture, and subsequent electrolysis of its redox content.…”

Detection of Bacterial Rhamnolipid Toxin by Redox Liposome Single Impact Electrochemistry

“…The UME is polarized at the oxidation or reduction potential of the encapsulated redox probe and a concentration of several pico-molar of redox liposomes added to the aqueous buffer electrolyte is enough to detect "current spikes" in the chronoamperometry (i-t) curve corresponding to discrete collision events. [23,[28][29][30][31][32][33][34][35][36] The electron transfer does not readily occur across a lipid bilayer, thus the electrolysis of the liposome redox active content after collision and membrane rupture or opening at the UME surface led to many studies dealing with the membrane permeation mechanism. [23,28,[30][31][32][33][34][35][36][37][38][39][40] Here, our work is based on the previous results where no current spike was observed in the chronoamperometry curve because the redox DMPC liposomes did not break during impact (or collision) onto the UME surface.…”

Mobile Microrobots for In Vitro Biomedical Applications: A Survey

“…For instance, extracellular vesicles (e.g., exosomes), which are membranous structures with a size ranging from tens of nanometers up to few micrometers, play an important role during the communication from one cell to another. Therefore, the sensing and investigation of a single extracellular vesicle is of high interest for medical applications such as cancer monitoring and treatment [140], [141], although a better understanding of their functions and behaviors is still needed. Devices such as AFM and optical tweezers are capable of handling targets in this size range [142], although they fall short in dexterity and maneuverability compared to mobile microrobots due to their tethered nature.…”