GUV growth in response to LCNP addition was also observed to correlate with an increase in membrane permeability. A membrane-impermeable dextran (10 kDa) labelled with Alexa Fluor 488 (AF488) or Cascade Blue was added to the extra-vesicular medium. These passive membrane permeability probes were observed to leak into the lumen of the GUVs over time. GUV leakage to these probes was observed to be stochastic and hence variable between different GUVs in a sample, evident by the different degrees of dextran leakage shown in Fig. with unleaked, partially leaked and fully leaked GUVs. Further evidence for the stochastic enhanced permeability of the GUVs induced by MO lipids can be seen in the correlation between vesicle growth (or swelling) and the onset of vesicle leakage (Fig, ).