Morphological manipulation of bolaamphiphilic polydiacetylene assemblies by controlled lipid doping.

Morphological transformations of bolaamphiphilic polydiacetylene (L-Glu-Bis-3) lipid assemblies from helical ribbons to vesicles and flat sheets through controlled doping are described, and the role of specific lipid dopants in these processes is discussed. Upon doping with cell surface receptor G(M1) ganglioside, fluid vesicular structures start to emerge, coexisting with the micro-crystalline helical ribbons. The vesicle formation is further facilitated and stabilized by the introduction of cholesterol into the system, presumably through surface curvature variation induced by inhomogeneous distribution and dynamic clustering of G(M1) and cholesterol within the doped assemblies. Extended helical ribbons are "truncated" into patches of flat sheets when a sufficient amount of Bis-1, a structurally compatible symmetric bolaamphiphilic diacetylene lipid, is doped. The results reaffirm the important roles of packing geometry and headgroup chirality in the formation of extended helical ribbon structures. The doped assemblies of bolaamphiphiles allow for capture of intermediate structures of morphological transformation using transmission electron microscopy (TEM). A vesicle-to-ribbon transformation mechanism via lateral reorganization within relatively fluid vesicular microstructures has been suggested. Understanding of the doping-induced transformation process provides useful information for the design of advanced materials where the microscopic morphology of material is crucial to its function.