Reaction and Diffusion Phenomena in Biomimetic Nanoscale Reactors and Networks

Doktorsavhandling, 2005

Methods for construction of geometrically complex, fully connected surface-immobilized microscopic networks of phospholipid bilayer vesicles (1-50 µm in diameter) interconnected by lipid nanotubes (100-300 nm in diameter), have been developed. The networks have controlled connectivity and are well-defined with regard to the container size, content, angle between nanotube extensions, and nanotube length. Within networks, the nanotubes spontaneously arrange themselves into three-way junctions with an angle of 120° between each nanotube, by minimizing the tube length. Using a combination of microelectrofusion, spontaneous nanotube pattern formation, and satellite-vesicle injection, complex networks of containers and nanotubes can be produced for a range of applications in, for example, nanofluidics and artificial cell design. In addition, this electrofusion method allows integration of biological cells into lipid nanotube-vesicle networks. A micropipette-assisted writing technique for formation of two-dimensional networks of phospholipid vesicles and nanotubes on functionalized and patterned substrates was also developed. The method allows for formation of networks with a large number of nodes and vertexes with well-defined geometry and surface adhesion, and represents a first step toward very large scale integration of nanotube-vesicle networks in, for example, nanofluidic applications. The networks are used in order to initiate chemical reactions involving few reactants inside the micrometer-scale biomimetic vesicles (10-12 to 10-15 L). The shape of these networks is under dynamic control, allowing for transfer and mixing of two or several reactants at will. Reactions could be followed for systems having as few as approximately 15 enzyme molecules confined to a reactor vesicle. Also, changes in the geometrical properties of a small-scale reaction container are found to alter the dynamics of a reaction-diffusion system with a diffusing catalyst (enzyme). A transition from a compact geometry (sphere) to a structured geometry (several spheres connected by nanoconduits) in nanotube-vesicle networks induces an ordinary enzyme-catalyzed reaction to display wave-like properties. The key to this behavior is the small diameter of the conduits placed between ideally mixed containers which act as diffusion-barriers of catalyst.