Fig. 4: Membrane fusion between cubosome and exosome.

a Scheme of describing the Fluorescence Resonance Energy Transfer (FRET) experiment for understanding fusion kinetics at different exosome: cubosome ratio and buffer. As fusion progresses, the energy transfer between FRET pair is decreased. The fluorescence intensity decrease of acceptor, Liss Rhod dye, was used as a lipid mixing indicator. Cubosomes were used as a control for comparison before fusion occurred. b Changes in fluorescent intensity of Liss Rhod intensity in Deionized water (D.W.) and PBS when the exosome: cubosome number ratio is 1:1. c Changes in Liss Rhod intensity in D.W. and PBS when the exosome: cubosome number ratio is 10:1. d SAXS scan results for solution of cubosome and exosome mixture. Under D.W. conditions, measurements were taken every 10 s for 10 min when the exosome: cubosome concentration ratio was 10:1. As fusion progresses, the intensity of the first Bragg peak indicating cubic phase is decreased. e Changes in the first peak of the cubic phase in D.W. and PBS when the exosome: cubosome concentration number ratio is 1:1. f Changes in the first peak of the cubic phase in D.W. and PBS when the exosome: cubosome concentration number ratio is 10:1. g Scheme showing the difference in the membrane fusion kinetics in D.W. and PBS due to charge screening. h DLS results in D.W. and PBS when the exosome: cubosome concentration ratio is 1:1 and 10:1. Data are presented as mean ± SE, n = 3. i Fluorescence image of hybrid exosome showing only the exosome labeled by DiI. j Fluorescence image of hybrid exosome showing only the cubosome labeled by NBD-PE. k Fluorescence image of hybrid exosome. Exosome and cubosome overlap and yellow signal observed, supporting a completion of membrane fusion. l Cryo-TEM image of the fusion process between exosome and cubosome. m Loading efficiency of doxorubicin, immunoglobulin G, and mRNA into exosomes. Data are presented as mean ± SE, n = 3.