(104f) Directed Aggregation and Fusion of Vesicles Induced By a DNA-Surfactant

Conventional synthetic strategies have provided a number of attractive molecular devices, but the sizes of the devices produced using these strategies are limited to a few hundred nanometers at most. Molecular self-assembly is an alternative approach for constructing systems that are larger (submicrometers to micrometers) and more complex. In particular, lipid vesicles, which are spherical bilayer shells encapsulating an aqueous interior, have been widely studied as a biomimetic example of molecular self-assemblies. Such lipid vesicles can range in size from 50nm to ∼1mm, and contain various compounds, including metal ions, macromolecules and biomolecules. Furthermore, modification of the lipid bilayer can confer diverse functions onto lipid vesicles. Higher order or secondary levels of self-assembly of lipid vesicles have been achieved through vesicle aggregation using electrostatic and ligand–receptor interactions. These higher ordered assemblies of lipid vesicles were also studied as a simple model for biological tissues.

Over the last decade, oligonucleotides have attracted much attention as intelligent materials due to their highly specific and designable binding properties toward their complementary sequences. Many researchers have employed oligonucleotides as building blocks to construct nanostructured systems with well-designed geometric shapes and sizes. Besides, oligonucleotides have been used as molecular glues for cross-linking, immobilizing and aggregating proteins, nanoparticles, colloids and cells. Oligonucleotides were also introduced to the vesicles and utilized for the immobilization of vesicles on an electrode or a plate. Patolsky et al. utilized the DNA-tethered vesicles for amplification of hybridization signal. Yoshina-Ishii and Boxer first reported the sequence-specific immobilization of lipid vesicles. These studies suggested the utility of DNA-tethered vesicles. Most of them mainly focused on surface modification and nanofabricated structures, rather than on the construction of macroscopic structured systems. Wu et al. reported that an extremely high concentration (10mg/ml) of long linear DNA-induced non-selective aggregation of a small portion of zwitter ionic vesicles, where the aggregation was supposed to be induced not by the DNA hybridization but simply by the electrostatic interaction. Graneli et al. first reported the interaction among DNA-tethered vesicles on a DNA-modified gold substrate and succeeded in the formation of three-dimensional vesicle matrices based on DNA hybridization. There are, however, considerable uncertainties on the DNA-directed aggregation of vesicles in solution. For example, are the DNA-tethered vesicles responsive to external stimuli such as temperature, ionic strength, etc.? Here, we investigate DNA directed aggregation of vesicles in solution using DNA-surfactants and clarify if the DNA-tethered vesicle possesses the DNA-derived characteristics to be responsive to external stimuli. Furthermore, we successfully accomplished DNA-directed fusion of vesicles based on this assembly procedure, leading to the production of a micro-reactor involving an enzyme-catalyzed reaction in the giant vesicle produced.