Small Extracellular Vesicles (sEVs) have been recently explored as drug/gene delivery nanocarriers due to their ability to penetrate tumours or cross the blood brain barrier. In addition, they may produce longer circulation time compared with traditional nanoparticles. Nevertheless, so far, how to identify most suitable sEVs for drug delivery has not been clearly clarified.
To identify most suitable sEVs from mesenchymal stem cells (MSCs) and cancer cells (U937- human myeloid leukaemia cell line, THP-1- human acute monoblastic leukaemia cell line, and MIA PaCa-2- pancreatic cancer cells) for potential tumour targeted intracellular drug delivery.
Differential ultracentrifugation method was used to isolate sEVs from culture medium. Particle size and concentration were analysed by nanoparticle tracking analysis, while surface charge was measured by dynamic light scattering technique. The morphology was visualized by Transmission Electron Microscopy (TEM). Western blot was used for analysing sEVs markers including CD81 and TSG101 to confirm the sEVs isolation.
The size of sEVs from different cells was different (140-180 nm). They were all spherical, “cup”-shaped and negatively charged with a zeta potential from -21.2 to -28.9 mV. They were stable in PBS up to 8 weeks at 4°C. MSCs and MIA PaCa-2 cells produced more sEVs. Different protein amount was found in 1010 sEVs: MSCs (152.6 ± 12.6 mg), U937 (15.17 ± 1.0 mg), THP-1 (14.4 ± 3.8 mg), and MIA PaCa-2 (57.0 ± 5.7 mg). The presence of TSG101 and CD81 further confirmed the sEVs isolation.
The sEVs from different cells varies in size, and protein expression. MSCs derived sEVs was preferred for drug delivery as MSCs have high production rate and high protein expression in the sEVs. However, the ability to penetrate tumour are yet to be determined.