# Plant Exosomal Vesicles: Perspective Information Nanocarriers in Biomedicine
## 1 Introduction  
The discovery and development of new effective pharmaceuticals are considered as priority outcomes of biomedical science, aimed to improve the quality of human life. In recent years, significant advances have been made in this field, which have led to the development of many new drugs, including low-molecular-weight compounds of natural and synthetic origin, therapeutic proteins, and nucleic acids [1, 2, 3, 4]. However, an important issue of therapy is the delivery effectiveness of these molecules to target cells or tissues. The targeted delivery makes it possible to create the required dose of an effector in the right location, protects it from degradation, reduces the toxic impact, and makes the therapy process more economical [5, 6].  
Many materials and approaches for delivery have been developed to date by the means of inorganic and organic platforms. Inorganic carriers include various nanoparticles, mainly based on metals and silica, as well as various combinations thereof [7, 8]. The particles are functionalized with active groups, such as amine, carboxyl, and thiol, that allow them to chemically bind bioactive substances [9]. In particular, the mesoporous silica nanoparticles attract a lot of attention as promising carriers due to their high surface area and pore volume [10]. The carbon-based nanomaterials, especially graphene and multi-walled carbon nanotubes, also have a great potential for encapsulation and controlledrelease of bioactive compounds [11]. Still, limitations, such as particle aggregation in biological fluids and high cost of production, may restrict their use in practical applications.  
Organic nanocarriers based on proteins (e.g., zein, gladin, albumin) and polysaccharides (e.g., chitosan, alginate, cellulose) are promising candidates for targeted drug delivery [12]. The natural biopolymers used for their fabrication ensure the improved biological compatibility of such platforms, along with other advantages of nanosized materials. However, the low stability may limit their medical application in particular cases. Liposomes are simple vesicular structures and have been widely used as transporters for about 40 years [13]. Due to the use of physiological lipids as building blocks, liposomes have many advantages in transdermal, topical, and pulmonary applications [5]. However, the short half-life and production cost of such systems limit their therapeutic use [14]. The lipid nanoparticles represent a new delivery method, with improved properties compared to liposomes, including the ease of fabrication processes and stability [15]. They became particularly well known worldwide due to their use as the mRNA-containing vaccines for coronavirus (COVID-19) developed by Moderna and BioNTech/Pfizer. Such problems as the low drug-loading efficiency and lack of sufficient clinical observation should be solved to promote further the benefits of these carriers [16]. In addition to the above-mentioned delivery methods, the biological vectors derived from bacteriophages, mammalian, and plant viruses are also clinically used [17].  
Exosomal nanoparticles from various biological objects, including mammals, plants, fungi, and bacteria have emerged as a new category of membrane vectors [17]. The practical application of plant exosomes requires a solid scientific basis and understanding of their biogenesis, molecular composition, physical characteristics, and biological properties as well as safety and effectiveness in disease treatment. Actually, thorough research in this field has only recently begun and thus many questions remain unsolved. In this review, we aimed to review critically the current achievements and challenges in terms of the possible use of plant exosomes as potential therapeutic agents and regulators of cellular networks.