TABLE 2.

Synthesis classification and characteristics of engineered exosomes.

Classification	Producing method	Cargos	Advantages	Disadvantages	Application	References
Parent cell modification	Transfection	MicroRNA	Wide application	Transfection efficiency variable; Low loading efficiency	Engineered exosomes promote diabetic wound healing by enhancing angiogenesis, fibrogenesis, and re-epithelialization	Huang et al. (2021b)
		LncRNA			HOTAIR overexpressed stem cell exosomes promote the angiogenesis and wound healing of chronic diabetic wounds	Born et al. (2022)
	Co-incubation	Protein	Convenient	Potentially cytotoxic; inefficient loading; Suitable for hydrophilic substances	After IFN-γ stimulation, the overexpression of PD-L1 on exosomes inhibits overactive immune cells and promotes wound healing	Su et al. (2019)
		MicroRNA			Overexpression of miR-1260a in exosomes enhanced osteogenesis and angiogenesis in bone mesenchymal stem cells treated with magnetic nanoparticles combined with static magnetic field	Wu et al. (2021)
Exosome loading	Co-incubation	Curcumin	Enhance the solubility of drugs	Low drug loading rate; Limited application; Suitable for hydrophobic molecules	Curcumin-exosomes possess anti-inflammatory activity and have good therapeutic effect on mice with septic shock induced by lipopolysaccharide (LPS)	Sun et al. (2010)
	Electroporation	MicroRNA	High loading rate; Able to incorporate large compounds	Size-dependent; Exosome aggregation; siRNA loading efficiency variable	Adipose stem cell exosomes overexpressing miR-21-5p promote diabetic wound healing	Kooijmans et al. (2013)
	Ultrasonic	Silver nanoparticles	Stable; high loading rate	Not suitable for thermosensitive compounds	Exosomes carrying AgNP, with antibacterial properties, can accelerate collagen deposition, angiogenesis, and nerve repair to enhance wound healing	Qian et al. (2020)
Exosome surface modification	Genetic engineering	Targeting peptide	Targeting	Need to be characterized	Targeted peptides could be introduced onto the exosome surface by genetically engineered, providing tissue specificity and improving efficacy	Curley et al. (2020)
	Click chemistry	Targeting peptide	Fast reaction time; high specificity	Need to be characterized; A two-step procedure with subsequent purification steps to remove unbound molecules and activate agents	Targeting peptides - Cardiac homing peptides are coupled to cardiac stem cell exosomes to improve their targeting and enhance the uptake of exosomes by cardiac myocytes	Vandergriff et al. (2018)
Artificial synthesis	Top-down	Like parent cells	High purity; large yield	Cargo loading lacks specificity	After passing embryonic stem cells (ES) through micropores, exosome-like microvesicles are obtained, which promote the proliferation of fibroblasts and contribute to tissue recovery or wound-healing processes	Jeong et al. (2014)
	Bottom-up	Protein	Controllable production process; high purity; large yield	Complex operating procedures	By combining bioactive protein with liposome, artificial exosomes with specific co-function were obtained, which reduced synovial hyperplasia and inflammation of rabbit knee joint and had therapeutic effect on rheumatoid arthritis	Martinez-Lostao et al. (2010)