From algal cells to autofluorescent ghost plasma membrane vesicles

Plasma membrane vesicles can be effective, non- toxic carriers for microscale material transport, provide a convenient model for probing membrane- related processes, since intracellular biochemical processes are eliminated. We describe here a fine- tuned protocol for isolating ghost plasma membrane vesicles from the unicellular alga Dunaliella tertiolecta, and preliminary characterization of their structural features and permeability properties, with comparisons to giant unilamellar phospholipid vesicles. The complexity of the algal ghost membrane vesicles reconstructed from the native membrane material released after hypoosmotic stress lies between that of phospholipid vesicles and of cells. AFM structural characterization of reconstructed vesicles shows a thick envelope and a nearly empty vesicle interior. The surface of the envelope contains a heterogeneous distribution of densely packed, nanometer-scale globules and pore-like structures which may be derived from surface coat proteins. Confocal fluorescence imaging reveals the highly pigmented photosynthetic apparatus located within the thylakoid membrane and retained in the vesicle membrane. Transport of the fluorescent dye calcein into ghost and giant unilamellar vesicles reveals significant differences in permeability. Expanded knowledge of this unique membrane system will contribute to the design of marine bio-inspired carriers for advanced biotechnological applications.