Single Giant Vesicle Rupture Events Reveal Multiple Mechanisms of Glass-Supported Bilayer Formation

¹ Texas A&M Health Science Center
² Texas A&M University

^* To whom correspondence should be addressed. E-mail: smusser{at}tamu.edu.

Submitted on July 21, 2006
Revised on September 26, 2006
Accepted on 30 November 2006

	Abstract

The formation of supported lipid bilayers (SLBs) on glass from giant unilamellar vesicles (GUVs) was studied using fluorescence microscopy. We show that GUV rupture occurs by at least four mechanisms including: (1) spontaneous rupture of isolated GUVs yielding almost heart-shaped bilayer patches (asymmetric rupture); (2) spontaneous rupture of isolated GUVs yielding circular bilayer patches (symmetric rupture); (3) induced rupture of an incoming vesicle when it contacts a planar bilayer edge; and (4) induced rupture of an adsorbed GUV when a nearby GUV spontaneously ruptures. In pathway (1), the dominant rupture pathway for isolated GUVs, GUVs deformed upon adsorption to the glass surface, and planar bilayer patch formation was initiated by rupture pore formation near the rim of the glass-bilayer interface. Expanding rupture pores led to planar bilayer formation in 10-20 ms. Rupture probability per unit time depended on the average intrinsic curvature of the component lipids. The membrane leaflet adsorbed to the glass surface in planar bilayer patches originated from the outer leaflet of GUVs. Pathway (2) was rarely observed. We surmise that SLB formation is predominately initiated by pathway (1) rupture events, and that pathway (3) and (4) rupture events dominate during later stages of SLB formation.

Key Words: bilayer pores, fluorescence microscopy, giant unilamellar vesicles, lipid curvature, vesicle fusion