Current Strategies for Exosome Cargo Loading and Targeting Delivery

Abstract

Extracellular vesicles (EVs) such as ectosomes and exosomes have gained attention as promising natural carriers for drug delivery. Exosomes, which range from 30 to 100 nm in diameter, possess a lipid bilayer and are secreted by various cells. Due to their high biocompatibility, stability, and low immunogenicity, exosomes are favored as cargo carriers. The lipid bilayer membrane of exosomes also offers protection against cargo degradation, making them a desirable candidate for drug delivery. However, loading cargo into exosomes remains to be a challenge. Despite various strategies such as incubation, electroporation, sonication, extrusion, freeze–thaw cycling, and transfection that have been developed to facilitate cargo loading, inadequate efficiency still persists. This review offers an overview of current cargo delivery strategies using exosomes and summarizes recent approaches for loading small-molecule, nucleic acid, and protein drugs into exosomes. With insights from these studies, we provide ideas for more efficient and effective delivery of drug molecules by using exosomes.

Tonicity-induced cargo loading into extracellular vesicles

“…27,30 Here, we conducted a comparative analysis between the TC method and traditional loading methods, including sonication and extrusion, employing experimental conditions commonly used in previous reports. 55,56…”

“…In the extrusion method, the EVs were extruded through a 0.2 μm pore syringe filter (Pall Corporation, USA) 20 times. 55 In the case of the sonication method, the EVs were sonicated for six cycles, with the “on mode” lasting 30 s and the “off mode” lasting 150 s according to a previous report. 56 After loading, extrusion, or sonication, the free drugs were washed using Exodisc under the same conditions.…”

Engineered Exosomes as Theranostic Platforms for Cancer Treatment

“…Chemical transfection is a method of incubating drugs or genes with donor cells to make cells secrete drug-carrying exosomes using a commercial transfection agent. The transfection method is an effective and stable approach for encapsulating therapeutic agents, especially for loading RNA, peptides and proteins . For example, Warren et al reported an engineered bovine milk exosome (mExo)-based system that was capable of oral delivering small interfering RNA (siRNA) orally.…”

“…The transfection method is an effective and stable approach for encapsulating therapeutic agents, especially for loading RNA, peptides and proteins. 110 For example, Warren et al reported an engineered bovine milk exosome (mExo)-based system that was capable of oral delivering small interfering RNA (siRNA) orally. The mExo coated by polyethylene glycol (PEG) showed increased stability in acidic gastric environment and enhanced mucin penetration capability.…”

Nucleic Acid Delivery Nanotechnologies for In Vivo Cell Programming

“…Packaging nucleic acids of interest into extracellular vesicles can be challenging because they are inherently “full” of endogenous RNA and proteins . Some common methods to increase nucleic acid loading efficiency include overexpression of the cargo in source cells prior to EV isolation or postisolation loading using electroporation or sonication methods. , Similarly, surface engineering of EVs using genetic manipulation or metabolic engineering of the source cell can provide additional targeting capabilities and improve pharmacokinetics. , There are also ongoing efforts to improve large scale EV manufacturing, including the development of cellular nanoporation techniques that simultaneously increase exosome secretion and RNA encapsulation . Currently, there are no FDA-approved EV-based treatments .…”