Dynamic Fingering in Adhered Lipid Membranes

Artificial lipid
membranes incorporating proteins have frequently
been used as models for the dynamic organization of biological structures
in living cells as well as in the development of biology-inspired
technologies. We report here on the experimental demonstration and
characterization of a pattern-forming process that occurs in a lipid
bilayer membrane adhered via biotin–avidin binding to a second
lipid membrane that is supported by a solid substrate. Adhesion regions
are roughly circular with a diameter of about 25 μm. Using confocal
fluorescence microscopy, we record time series of dynamic fingering
patterns that grow in the upper lipid membrane and intermembrane biotin–avidin
bonds. The fingers are micrometer-scale elongated pores that grow
from the edge of an already-stabilized hole. Finger growth is saltatory
on the scale of tens of seconds. We find that as the fingers grow
and the density of adhesion proteins increases, the rate of finger
growth decreases exponentially and the width of newly formed fingers
decreases linearly. We show that these findings are consistent with
a thermodynamic description of dynamic pore formation and stabilization.