The term bioelectricity might conjure up images of Victor Frankenstein, or perhaps unscrupulous quack doctors in traveling medicine shows. Despite the warped public perception, electrochemical potentials are indeed a fact of life, influencing processes in transport, metabolism, computation, and development across all the biological kingdoms. By developing devices that interface with these bioelectric systems, engineers may be able to observe or even control these processes for sensing, manufacturing, or medical applications that were not possible before.
There’s a complication: the wet, salty electrochemistry that comprises most bioelectric systems is not immediately compatible with the integrated circuits that drive our digital world. Care must be taken at the interface between electronics and living organisms to keep both the electronics and organisms happy. This interface has been at the core of my research work, whether it involves the electroactive bacterium Shewanella oneidensis or skin cells sheepherded in a petri dish. I am engineering devices that use this bioelectrical connection to augment these biological systems for biosensing and medical applications.
SCHEEPDOG: Steering cell motion with electrical stimulation
I developed SCHEEPDOG, a device that exploits electrotaxis, the ability of cells to sense electric fields and follow them, to shepherd cell migration. SCHEEPDOG uses two orthogonal electrode pairs, one vertical and one horizontal, to create a composite field direction. By adjusting field directions over time, cells can be herded along arbitrary trajectories, akin to how an ‘Etch A Sketch’ traces out a picture via two control knobs. With SCHEEPDOG, we have induced a potpourri of novel dynamic maneuvers in skin and kidney cells: 90-degree turns, diagonals, sinusoids, and circles (pictured above). The level of control demonstrated suggests that cells effectively time-average electric field cues on the order of ~5 minutes, which helps to clarify the time scales involved in the biological response. Because electrotaxis has been documented across diverse systems including at least 20 mammalian cell types, slime molds, fish, and frogs, our platform represents a control approach with potentially broad utility in many arenas.