Bridging the biology-electronics communication gap with redox signaling

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Electronic and biological systems both have the ability to sense, respond to, and communicate relevant data. This dissertation aims to facilitate communication between the two and create bio-hybrid devices that can process the breadths of both electronic and biological information. We describe the development of novel methods that bridge this bi-directional communication gap through the use of electronically and biologically relevant redox molecules for controlled and quantitative information transfer. Additionally, we demonstrate that the incorporation of biological components onto microelectronic systems can open doors for improved capabilities in a variety of fields.

 First, we describe the original use of redox molecules to electronically control the activity of an enzyme on a chip. Using biofabrication techniques, we assembled HLPT, a fusion protein which generates the quorum sensing molecule autoinducer-2, on an electrodeposited chitosan film on top of an electrode. This allows the electrode to controllably oxidize the enzyme in situ through a redox mediator, acetosyringone. We successfully showed that activity decrease and bacterial quorum sensing response are proportional to the input charge. 

 To engineer bio-electronic communication with cells, we first aimed for better characterizing an electronic method for measuring cell response. We engineered Escherichia coli (E.coli) cells to respond to autoinducer-2 by producing the β-galactosidase enzyme. We then investigated an existing electrochemical method for detecting β-galactosidase activity by measuring a redox-active product of the cleavage of the added substrate molecule PAPG. In our novel findings, the product, PAP, was found to be produced at a rate that correlated with the standard spectrophotometric method for measuring β-galactosidase, the Miller assay, in both whole live and lysed cells. Conversely, to translate electronic signals to something cells can understand, we used pyocyanin, a redox drug which oxidizes the E.coli SoxR protein and allows transcription from the soxS promoter. We utilized electronic control of ferricyanide, an electron acceptor, to amplify the production of a reporter from soxS. With this novel method, we show that production of reporter depends on the frequency and amplitude of electronic signals, and investigate the method’s metabolic effects. Overall, the work in this dissertation makes strides towards the greater goal of creating multi-functional bio-hybrid devices.