FIGURE 4.
Exosomes and parental cells membrane fluidity and lipid phase state at different pH conditions. A, shown are Laurdan GP values (340-nm excitation wavelength; 37 °C) of buffered and acidic Mel1 cells (open bars) and exoMel1 and exoMel1ac (filled bars). The higher GP values of exosomes indicate a higher rigidity of such membranes with respect to bulk of the cellular membranes. ExoMel1ac are significantly more rigid than exoMel1. Data are the means ± S.E. of at least three independent experiments. *, p < 0.05 versus the corresponding bulk cellular membranes. B, Laurdan excitation GP spectra of Mel1 (a, filled triangles), Mel1ac cells (b, filled circles), exoMel1 (c, open triangles), and exoMel1ac (d, open circles) at 37 °C. Laurdan GP values decrease by increasing excitation wavelength, indicating that both cell and exosome membranes are in a liquid-crystalline lipid phase in the absence of coexisting gel-phase lipid domains. The curves are representatives of three consistent experiments.