Employing extracellular vesicles for non-invasive renal monitoring: A captivating prospect

Table 1 Methods used for the isolation of urinary extracellular vesicles

Technique	Type	Advantage(s)	Disadvantage (s)	Purity	Ref.
Centrifugation	Differential	Easy to perform	Co-purification of protein aggregates (THP) Inability to separate exosomes from microvesicles Lengthy Impractical for large-scale studies	++	[37,44,50,52,69,92]
	Sucrose gradient	No mechanical stress and hence allows the collection of morphologically intact particles Removes THP	High sucrose concentration may affect the biological functions of exosomes Inability to separate exosomes from particles with similar density and size Difficult and lengthy Impractical for large-scale studies	+++++	[23,50,54,55]
	Sucrose cushion	No mechanical stress and hence allows the collection of morphologically intact particles	Inability to separate exosomes from particles with similar density and size Difficult and lengthy Impractical for large-scale studies	+++++	[33,56,57,78,80]
Filtration	Nanofiltration	Easy to perform	Low purity grade Co-purification of protein aggregates (THP) Low exosome yield due to their lost on the surface of the nano-membrane	+++	[94]
	Microfiltration	Easy to perform Rapid Maintain vesicle structure	Co-purification of protein aggregates (THP) Inability to separate exosomes from microvesicles	+++	[59]
Immunoaffinity separation	Immunobeads	Allow rapid semi quantitative characterization of the surface phenotype can be tissue-specific	Not suited for large sample volumes Captured extracellular vesicles may not retain biological functionality even if successfully eluted from bead surface Co-purification of protein aggregates (THP) Low yield	++	[57,61,62]
Commercial kits	Total Exosome Isolation Reagent-Invitrogen™ Exomir™ Exo-Spin™ Exotest™ Exosome Dynabeads® miRCURY™ ExoQuick-TC™ and DiagExo®	Rapid and requires low sample volume Practical	Impractical for large-scale studies Reproducibility, yield and sample quality should be checked case by case Co-purification of protein aggregates (THP)	++

THP: Tamm-Horsfall protein.