With growing interest in nanotechnology, various nano-based products and applications have been developed. The use of these nanotech-based materials for medical purposes termed as nanomedicine. Basically, nanomedicine refers to the use of nanoparticles (either of biological or non-biological origin) for the diagnosis, monitoring, prevention and treatment of diseases. Nanoparticles (NPs) have unique characteristics such as size, surface properties, shape, stability, and composition that make them relevant to physiological interactions. The unique physicochemical properties of NPs allow for a wide range of applications in modern medicine and other fields. A few examples of NP applications in biology and modern medicine are fluorescent biological labels, drugs and gene delivery, protein detections and cancer therapy. NPs are useful and have potential applications, but their entry into a physiological environment can present adverse effects, especially in terms of toxicity. For instance, liposomebased drugs showed inherent health problems such as rapid dissolution in the biological environment, poor storage, and inability to maintain stability. This and other unmentioned undesired effects of NPs on biomedical or nanomedicine applications, particularly to human health, lead us to seek alternative solutions for utilizing NPs in a safe manner. Extracellular vesicles (EVs), which are membrane-bound NPs secreted by most cells under physiological and pathological conditions, could offer a potential path to NP safety in the body and will potentially offer us the opportunity to exploit their unlimited potential, for example, for drug delivery system (DDS). EVs are highly heterogeneous evolutionary conserved entities that play a significant role in transferring functional cargo to nearby or distant cells, thus facilitating intercellular communication. They are known to influence both physiological as well as pathological processes. Novel methods for EV characterization have been developed to measure the size, particle size distribution, surface charge, morphology and concentration of vesicles resuspended in a certain medium.

Naturally, EVs exist as colloidal suspensions when resuspended in media carry a net negative charge due to the presence of glycosylated proteins, lipids, among others on their surfaces. This surface charge of EVs can be estimated by measuring their electrophoretic mobility, which is the basis for calculating their (zeta potential) ZP value. ZP is one parameter used to characterize EVs. ZP can be used as a tool to predict the colloidal stability of NPs or EVs in suspension. ZP allows to assess the initial contact between the NP and the cell membrane. Following this interaction, the uptake rate is determined by the particle size. As a result, ZP and particle size may influence physiological effects. To put it another way, controlling the size and ZP is crucial to the efficient use of NPs for DDS purposes. The colloidal stability of EVs is one of the crucial parameters for understanding their fates under different conditions while maintaining physicochemical properties and cargoes. Several methods can be used to