Table 1.

The principles, advantages, and limitations of the exosome loading methods

Loading strategy	Principle	Advantage	Disadvantage	References
Coincubation	By incubating the exosome or donor cell directly with the drug (typically a lipid-soluble small molecule), the drug can enter the exosome or donor cell by diffusion along a concentration gradient	Simple operation No additional active substance is required	Only fat-soluble drugs can be loaded Low loading efficiency	[109]
Extrusion	The exosomes were mixed with the drug, and the mixture was then loaded into a syringe-based lipid extruder with a 100-to 400-nm porous membrane at a controlled temperature. During extrusion, the exosome membrane is ruptured and violently mixed with the drug	High yield Suitable for mass production	The properties of the membrane (e.g., zeta potential) and membrane protein structure may be altered Potentially cytotoxic	[110]
Sonication	The exosomes were incubated with drug molecules, etc., and then the membrane of the exosomes was deformed by sonication and the mechanical shear force of the sonication probe to make the drug enter the exosomes	High drug loading efficiency	The drug may attach to the membrane surface Not effective against hydrophobic drugs	[111]
Electroporation	An electric field is applied to the exosome suspended in a conductive solution, and the current interferes with the phospholipid bilayer of the exosome, creating temporary holes in the membrane through which drugs, etc., can diffuse into the interior of the exosome	No chemical reagents are introduced High efficiency in loading hydrophilic drugs (e.g., DNA and RNA)	May result in the introduction of drugs that fuse with the cell's own components	[112]