A Voltage Controlled Ion Gate for Inclusion in a Biomimetic Excitable Cell

Pamela M. Norris
Mechanical and Aerospace Engineering, School of Engineering and Applied Science, UVa

Joseph R. Moorman
Cardiovascular Medicine, School of Medicine, UVa

The purpose of this project is to construct and demonstrate the functionality of a voltage controlled ion gate fabricated from electro-active polymers. Such an ion gate is a critical component in the conceptual design of a biomimetic excitable cell (gel-cell), through which ion species flow to produce distinct activated and resting phases, as found in the biological cardiac myocyte (CM). The grand vision of this research initiative to is connect the gel-cells into a large array to produce the first engineered excitable medium, an electro-active polymer analogy to heart tissue. Engineered excitable media have numerous potential applications including: 1) a new research approach to help elucidate the relationship between cardiac geometry and arrhythmias, 2) a bio-inspired peristaltic tube pump, and 3) a new class of artificial muscle. The gel-cell is composed of a thin ionic gating membrane made of polypyrrole (PPy) sandwiched between two areas of ionic liquid polymer gel (ILPG) embedded with potassium tracer ions. ILPG is a soft gelatinous material in which ions are suspended in a polymer matrix and free to move about. The PPy membrane, proposed to act as the voltage controlled ion gate, confines these ions to the upper chamber of the gel-cell and releases them when activated, just as excitable cardiac cells maintain ion gradients across their membrane until receiving a threshold signal for activation. PPy therefore functions in a manner similar to voltage-gated ion channels (VGICs) found in biology. Because a voltage controlled ion gate is the key enabling technology for producing a biomimetic excitable cell, the goal of the proposed work is to demonstrate the functionality of a voltage controlled potassium ion gate composed of a PPy membrane sandwiched between two regions of ionic liquid polymer gel. The proposed research will address the fabrication of the gel-based sandwich structure, demonstrate its functionality as a voltage controlled ion gate, determine how closely it matches physiologically relevant ion fluxes and time scales, and establish the key variables that can be used to optimize the ion gate for a given application.