Fig. 4
Mechanical characterization of RBC EVs. a Indentation behavior of 55 RBC EVs from donor 2 in a density plot. Colors indicate density of data points (blue and red indicate low and high density, respectively). Curves are shown until their first discontinuity. b Histogram of inflection points in the FDCs. Individual curves (gray dots show an example vesicle indentation in the inset) were smoothed (black curve, inset) and their derivative was taken (blue curve, inset). Main panel shows the location of the first peak of the derivative: 0.39 ± 0.02 Rc (s.e.m., N = 64 vesicles, in 8 cases no flattening was observed), 0.41 ± 0.02 Rc (s.e.m., N = 53, in 2 cases no flattening was observed) and 0.30 ± 0.04 Rc (s.e.m., N = 24, in 2 cases no flattening was observed) for the three donors, respectively. Black lines (solid, dashed and dotted for donor 1–3, respectively) show Gaussian fits. Red arrow indicates theoretically predicted value for a fluid vesicle. c Histogram of stiffness obtained by linearly fitting FDCs between 0.02–0.1 Rc. Lines represent Gaussian fits and line styles are equivalent to b. d Dimensionless pressure versus dimensionless stiffness. Theoretical prediction (solid red line) is based on an adaptation of Canham-Helfrich26,27 theory to describe mechanics of small vesicles28. Data for donors were individually fitted to the theoretical prediction with the bending modulus κ as parameter. For visualization of the data for the three donors (different style markers) in this plot, the average κ (15) of the donors was used
