Design of AC and DC biomimetic ion transport systems

Natural cells can convert chemical energy in the transmembrane ion gradient into electricity by membrane-protein-regulated ion transport. The underlying biophysics was studied in detail, and two artificial devices, an "AC biobattery" and a "DC biobattery", were designed to harness this biological electrogenic mechanism.;The design of the AC biobattery is the first effort to numerically design an artificial cell starting with molecular components and a defined objective. As a foundation, a model was created to describe the formation of the action potential (AP) in polarized cells. The model was used to quantify unknown channel parameters for the electrocyte, from Electrophorus electricus, extrapolating from measured APs. Models of optimally designed cells (ODC) are compared to experimental APs from natural electrocytes and a model of an axon. The ODC has similar behavior to the natural electrocyte, but a comparison of the two models shows that the ODC has 28% greater power output density and 31% higher energy conversion efficiency than the natural electrocyte. These findings are the starting point for additional studies of energy conversion for in vivo devices as well as the relationship between ion transporters and system performances of natural and artificial cells.;A biomimetic supported lipid membrane was fabricated on a nanofiber support. This nanofiber support mimics the function of cytoskeleton within a cell. Lipid bilayers were formed on a nanofiber mesh made from Nylon-6 fibers coated with mesoporous silica (SiO2). Lipid diffusivity and bilayer impedance were measured and found to be comparable to measurements from black lipid bilayers. Compared to current available bilayer fabrication techniques, this method offers the unique advantage of prolonging the lifetime while keeping both sides of the bilayer accessible.;The numerical design methodology developed for the AC biobattery was applied to optimize the design of a droplet-based "DC biobattery". The DC biobattery consists of two reservoirs of electrolyte with a common lipid bilayer and natural or engineered alpha-hemolysin inserted in the bilayer. The configuration of the DC biobattery was optimized to obtain the maximal energy output density. The DC biobattery was evaluated assuming it would be based on a droplet-interface-bilayer (DIB) device, which have shown significantly longer lifetimes (∼weeks) than black lipid bilayers (∼ 2 hrs).