Rupture of lipid vesicles near solid surfaces

The behavior of lipid vesicles near solid surfaces, despite its scientific and technological significance, is poorly understood. By simultaneously taking into account (i) the dynamics of spontaneous pore opening and closing in surface bound vesicles; (ii) their volume loss via leakage through the pores; (iii) and the propagation of their contact line, we have developed a simple model that can fully describe the detailed mechanism of and provide the necessary conditions for the rupture of vesicles and the subsequent formation of supported lipid bilayers. The predictions of the model are in qualitative agreement with many of the experimental observations.

Figure 1

Schematic picture of a surface-bound cap-shaped vesicle in the limit of strong adhesion, with a pore at the top.

Figure 2

Two examples of the time evolution of the three main geometrical variables ($V$, $r$, and $R$) for an initially spherical vesicle of size $R_0=280$ nm. System parameters are $\lambda =10$ pN, $W={10}^{-3}$ N/m, $c_{\mathrm{s}}=6\times {10}^3$ (top), $c_{\mathrm{s}}=3\times {10}^5$ (bottom).

Figure 3

The average time (based on 30 runs) needed for complete vesicle rupture (i.e., SLB formation) $\langle {\tau }_{\mathrm{rup}}\rangle$ as a function of $W$ and $c_{\mathrm{s}}$, for two vesicle sizes: $R_0=280$ nm (top row), $R_0=2.8$ $\mu \mathrm{m}$ (bottom row); and three line tensions: $\lambda =20$ pN (left column), $\lambda =10$ pN (middle column), $\lambda =5$ pN (right column). The data values are indicated by both color codes and contour lines (see the scales at the top right corner). $W_{\mathrm{crit}}^{\mathrm{therm}}$, $W_{\mathrm{crit}}^{\mathrm{pore}}$, and $W_{\min }\left(1\mathrm{ms}\right)$ are also plotted as gray dashed line, black dashed-dotted line, and black dotted line, respectively.

Figure 4

The average number of pores opened $\langle N_{\mathrm{pore}}\rangle$ (until either rupture or time ${10}^5$ s) for the same parameters as described in the legend of Fig. 3.

Figure 5

The average rupture time for three initial geometries: $R^{\mathrm{init}}=0.33R_0$ (left), $R^{\mathrm{init}}=R_0$ (middle), $R^{\mathrm{init}}=\sqrt{2}{R}_0$ (corresponding to zero initial volume, right), for $R_0=2.8$ $\mu \mathrm{m}$ and $\lambda =10$ pN. Colors and lines are as described in the legend of Fig. 3. $W_{\mathrm{crit}}^{\mathrm{init}}$ is also drawn as a gray dashed-dotted line.