Advancements in plant-derived exosome-like vesicles: Versatile bioactive carriers for targeted drug delivery systems

Abstract

Exosomes, small vesicles secreted by a wide range of cells, are found extensively in animals, plants, and microorganisms. Their excellent biocompatibility, efficient delivery capacity, and ease of membrane crossing have drawn significant interest as promising drug delivery carriers. Compared with their animal-derived counterparts, plant-derived exosomes (PDEs), in particular, stand out for their lower toxicity to human tissues, diverse sources, and enhanced targeted delivery capabilities. Advances in both in-depth research and technological development have enabled scholars to isolate exosomes successfully from various plants, exploring their potential in clinical therapies. However, the precise identification of PDEs and their drug delivery mechanisms remains an area of ongoing investigation. This review synthesizes the latest developments in the biogenesis, extraction, separation, and identification of PDEs, along with their engineering modifications and drug-loading strategies. We also delve into the therapeutic applications of exosomes and their future potential in drug delivery, aiming to elucidate the targeted delivery mechanisms of PDEs and pave new paths for clinical drug treatment.

Keywords: Delivery of drugs; Extracellular vesicles; Nanocarriers; Nanoparticles; Plant-derived exosomes.

Graphical abstract

Fig. 1

Exosome biogenesis and secretion pathway. (A) Biogenetic pathway and main composition of the exosomes. The formation of exosomes begins with endocytosis, which starts from invagination of the plasma membrane, leading to the generation of early endosomes. These endosomes progress to late endosomes, where the intraluminal vesicles mature into exosomes. The composition of exosomes is intricate, featuring surface markers such as CD63 and CD9, along with internal components, including nucleic acids, proteins, and lipids. Exosomes are subsequently released into the extracellular environment, where they are prepared for intercellular communication. Prepared using BioRender. (B) A transmission electron microscopy image of exosomes on the plasma membrane of a cell. An Epstein–Barr virus-transformed B-cell displaying newly expelled exosomes at the plasma membrane. Multivesicular bodies (MVBs) can be seen and can deliver their contents to the lysosomes for degradation or can fuse with the cell surface to release intraluminal vesicles as exosomes, as indicated by the arrows at the top of the picture. Reprinted from Ref. [10] with permission.

Fig. 2

Processes for isolating plant-derived exosomes (PDEs). (A) Ginseng and tomato-derived exosomes were obtained by ultracentrifugation and purified by a sucrose gradient [39,40]. (B) Ginger-derived exosomes were obtained by polyethylene glycol precipitation [41]. (C) Grapefruit-derived exosomes were obtained by electrophoretic dialysis [42]. (D) Cucumber-derived exosomes were obtained by high-pressure homogenization [43]. (E) Cabbage-derived exosomes were obtained by size exclusion chromatography [44]. Prepared using Figdraw.

Fig. 3

Comparison of nanovesicles isolated from Chinese cabbage and red cabbage by different methods. (A) Schematic illustration of exosome-like nanovesicle isolation from cabbage and the investigation of molecular functions (inflammation and apoptosis inhibition) and applications (drug delivery) of Cabex and Rabex. (B–D) Comparison of average size (B), EV yield (C), and nanovesicle purity (D) of Cabex between isolation methods. (E–G) Comparison of average size (E), nanovesicle yield (F), and nanovesicle purity (G) of Rabex between isolation methods (Green represents cabbage, and pink represents red cabbage) All values are expressed as mean ± standard deviation (SD) (^∗∗P < 0.01; ^∗∗∗P < 0.001; NS: not significant; n = 3). PEG: polyethylene glycol precipitation; UC: ultra-centrifugation; SEC: size exclusion chromatography. Reprinted from Ref. [44] with permission.

Fig. 4

Biogenesis pathways of plant-derived exosomes (PDEs) and targeting modes. PDEs are secreted by plant cells through three distinct pathways, feature a natural lipid bilayer structure on their surface, and contain various proteins and nucleic acids inside. These exosomes enter target cells to exert physiological effects through direct binding to receptors, membrane fusion, or endocytosis. MVBs: multivesicular bodies; EXPO: exocyst positive organelles; MHC: major histocompatibility complex. Prepared using Figdraw.

Fig. 5

Therapeutic applications of plant-derived exosomes (PDEs). PDEs can exert pharmacological effects on various diseases when injected into mice. For example, they have been used to treat glioma, liver cancer, and breast cancer, inhibit skin aging, treat osteoporosis, stimulate immune cell proliferation, and ameliorate colitis.

Fig. 6

The main methods of drug encapsulation and applications of plant-derived exosomes (PDEs). (A) Passive loading through an incubation has been used to prepare ginger-derived extracellular vesicles (EVs) encapsulating siRNA-CD98 [111] and grapefruit-derived EVs encapsulating the anti-inflammatory drug methotrexate (MTX) for treating colitis [112]. (B) Active loading through ultrasonication has been used to prepare grapefruit-derived EVs carrying cucurbitacin I (JSI-124) to inhibit GL-26 tumor growth [113]. (C) The combination of passive and active loading entails an incubation followed by sonication, where EVs are used to load heat shock protein 70 (HSP 70) for its antioxidant properties [114]. The choice and innovation of loading methods are crucial for improving the encapsulation efficiency, loading rate, and stability of PDEs. Prepared using BioRender.

Fig. 7

Mechanism of plant-derived exosome-mediated drug delivery. Plant-derived exosomes (PDEs) can be engineered to target specific disease sites by modifying the encapsulated drug. Upon reaching the body, they exert therapeutic effects on a range of conditions, including brain tumors, aortic coarctation, gastrointestinal inflammation, colon cancer, breast cancer, ulcerative colitis, ovarian cancer, and other metastatic liver diseases. Prepared using Figdraw.

Fig. 8

Schematic diagram of the process for preparing exosomes (Exo) nanoparticles and their application in Lu encapsulation. (A) The extraction and purification of Exos to encapsulate Lu. (B) Evaluation of the stability and anti-inflammatory activity of Exos@Lu. Molecular docking of Lu with Exos. (C) The 3D binding graph shows the optimal docking posture of the protein–Lu complex by visualization using PyMOL. Red: stick mode. (D, E) From left to right: 2D schematic diagram presenting the binding site and details of the amino acid residues of the protein interacting with Lu; optimal docking conformation and 3D structure of Lu complexed with the protein; and hydrogen bonds on the receptor surface of the optimal docking conformation between Lu and the protein. Reprinted from Ref. [133] with permission.

Fig. 9

Celery-derived exosomes deliver doxorubicin (DOX) to tumor sites to exert therapeutic effects. (A) Schematic diagram of the isolation of exosome-like nanoparticles (ELNs) from lemon, ginger, grape, and celery. (B) Body weight changes in the mice from the four groups (phosphate-buffered saline (PBS), DOX, CELNs-DOX, and liposome-DOX). The term “1 day” indicates the first day after drug injection. (C) Comparison of the body weights of the four groups of mice at the end of the experiments. (D) Comparison of the body sizes of the four groups of mice at the end of the experiment. (E) Photographs of each group of tumors. (F, G) The size (F) and weight (G) of the tumors in each group were evaluated. Reproduced from Ref. [138] with permission.