FIGURE 6.

Comparing different theoretical approximations for surface charge of small EVs. (a) A contour plot of the parameter κa as a function of particle size and ionic strength of the electrolyte, obtained using MATLAB. The parameter κa values are colored according to their acceptable range for (i) very large particles (a ≫ λ) fitted with Smoluchowski's approximation (κa ≫1, ideally for κa > 1000), (ii) very small particles (a ≪ λ) fitted with Hückel approximation (κa ≪1), and (iii) small EVs, representing a considerable Debye length even under high ionic strength of normal physiological conditions (λ > 0.7 nm). (b) ζ‐potential determined using Smoluchowski's, Hückel's, and Ohshima's approximations under different pH conditions for two experimental groups of HSA protein and small EVs. *p‐value < 0.05, **p‐value < 0.01, ***p‐value < 0.001, ****p‐value < 0.0001.