Research
Electrical Stimulation of Neural Cells in Patterned Cellular Network: Neural Interfaces
Repair and restoration of damaged neurological function by electrical stimulation is one of the most important questions in clinical therapy to treat Parkinson's disease, Alzheimer's disease, and injury caused to central nervous system. In this regard, functional stimulation (especially in the central nervous system) often demands small electrodes with high current density, which conflicts with the electrochemical safety requirements. Undesirable electrochemical change not only damages the electrodes but also causes abnormalities in neural function and cell structure. Furthermore, the neural interface requires smooth information exchange between the central nervous system and device. Both tasks require the transduction of electrical charges through an electrode-electrolyte interface, and the interface is characterized by its electrical impedance and the charge injection limit of the interfacial double-layer capacitances. Capacitive charge injection is an ideal mechanism for neural stimulation because no chemical change occurs to either the tissue or the electrode.
The research focuses on single cell electro-transduction experiments using a patterned cell network constructed to mimic the in vivo neural network, where a single cell is electrically stimulated by a novel electrical probe. The design of the new electrical probe for stimulation of a single cell involves electro-codeposition of poly (3, 4 ethylenedioxythiophene) (PEDOT)-carbon nanotubes (CNTs) on ion-milled platinum (and stainless steel) electrode of diameter ~20 µm. The metal electrode coated with PEDOT-CNT is characterized by charge injection limit of ~7 mC/cm2 and low impedance at 1 kHz. The grid pattern allows access to individual cells, while maintaining the environment that mimics a living system. Such an experimental system helps us understand how cells are stimulated and interact, as well as how they sense, generate and respond to the electrical stimuli. We are studying molecular events and pathways that govern transformation of the electrical signal into biochemical response and neuronal cell functions. The unraveling of mechanisms is of pivotal importance in developing strategies for restoring of neurological functions. Interesting possibilities are envisioned in the development of neural prostheses, where micro-patterned surfaces can be applied to define the interaction of neurological implant with the surrounding nervous system.
