Table 3 Examples of direct surface modification of EVs

Lipid insertion

DSPE-PEG

RGD

Tetraacetylated N-azidoacetyl-d-mannosamine (Ac4ManNAz)

Increased targeting to blood vessels and synergistic therapeutic angiogenesis effect and angiogenesis imaging

[136]

AA

PTX

Profound ability to accumulate in cancer cells upon systemic administration and improved therapeutic effects

[78]

Angiopep-2

Docetaxel

Targeted GBM delivery and therapy

[137]

Angiopep-2

Signal transducers and activators of transcription 3 (STAT3) siRNA

Xenograft growth inhibition due to BBB penetration, and enhanced median survival rate of the tumor-bearing nude mice

[138]

DOPE-PEG

RVG peptide

N.A

Improved targeting towards the cortex and hippocampus, greatly reduced plaque deposition and Aβ levels, decreased activity of astrocytes, and improved cognitive function of APP/PS1 mice, as determined by the Morris water maze test

[139]

Cholesterol

AS1411 aptamer

let-7 miRNA

Targeted breast cancer delivery and tumor growth inhibition

[140]

PSMA aptamer, EGFR aptamer and folate

Survivin siRNA

Tumor growth inhibition in prostate cancer xenograft, orthotopic breast cancer models, and patient derived colorectal cancer xenograft

[141]

Diacyllipid-PEG

Aptamer sgc8

Doxorubicin

Selective cancer cell targeting and high therapeutic efficacy in vitro

[142]

C18-PEG, DSPE-PEG, Cholesterol-PEG

AS1411 aptamer

PTX

Increased chemotherapeutic effects and decreased side effects in vivo

[143]

Chemical ligation

Amino group based EDC/NHS coupling chemistry and azide-alkyne cycloaddition chemistry

c(RGDyK) peptide

Curcumin (MSC-derived EVs)

Ischemic brain tissue targeting in the transient middle cerebral artery occlusion mice model, and strong suppression of the inflammatory response and cellular apoptosis in the lesion

[82]

c(RGDyK) peptide

miR-210

Ischemic brain tissue targeting in the transient middle cerebral artery occlusion mice model and enhanced animal survival rate

[145]

Neuropilin-1-targeted peptide (RGE)

Superparamagnetic iron oxide nanoparticles and curcumin

BBB penetration, good results for targeted imaging and therapy of glioma in the orthotopic glioma model

[144]

Thiol group based thiol-maleimide conjugation

Alexa488 (for imaging)

N.A

Quantitative analysis of the cellular delivery and intracellular traffic of EVs

[146]

Metabolic labeling

Azide group originating from L-azidohomoalanine supplement or tetra-acetylated N-azidoacetyl-D-mannosamine in culture medium

Biotin/FITC

N.A

Imaging analysis of EVs in cells and excellent potential for targeted delivery

[147]

Azide group originating from tetra-acetylated N-azidoacetyl-D-mannosamine in culture medium

Azadibenzylcyclooctyne-fluorescent dyes

N.A

Analysis of the uptake and distribution of EVs in vitro and in vivo

[148]

Affinity binding

CP05

M12 peptide

Phosphorodiamidate morpholino oligomer

enhanced dystrophin-positive myofibers in muscles and functional rescue

[149]

Thioketal-mPEG (assisted by Chlorin e6 and ultrasound irradiation)

Bmp7 mRNA

Phagocytosis escape from non-target organs, targeted delivery of Bmp7 mRNA into omental adipose tissue (OAT) and induced OAT browning

[151]

N.A

KV11 peptide

Greatly enhanced anti-angiogenic effects over KV11 peptide

[152]

Transferrin

Superparamagnetic nanoparticles

Doxorubicin

Excellent in vivo targeting ability and cancer inhibition effect

[153]

C1C2 domain of lactadherin

EGFR nanobody

N. A

Specific uptake by EGFR-overexpressing tumor cells

[157]

(RGD)-4C peptide

Neural progenitor cell derived-EVs

Lesion region targeting and suppressed inflammatory response in the MCAO mouse model

[158]

GPI anchor signal peptide derived from DAF

Anti-EGFR nanobodies

N.A

Improved EV binding to EGFR-expressing tumor cells

[135]

HepG2 cells derived EVs

Aptamer LZH8

FITC conjugated by DNA hybridization chain reaction

Fluorescence modification of specific EVs

[154]

Enzymatic conjugation

Vesicle membrane protein containing N-terminal glycine and leucine residues

EGFR-targeting peptides or anti-EGFR nanobodies

PTX

Increased accumulation in EGFR-positive cancer cells and significantly increased drug efficiency in a xenografted mouse model of EGFR-positive lung cancer

[156]