A Direct Gene Circuit - Electronic Interface for Cell-Free Synthetic Biology

Cell-free systems are emerging as key platforms for application-driven synthetic biology. Unlike their cell-based counterparts, cell-free systems can be assembled without the laborious task of moving engineered elements into cells or the balancing of their function within the context of complex endogenous molecular programs. While potential applications for cell-free systems are wide-ranging, their biosafe format makes them especially well-suited for de-centralizing sensing and diagnostics. To date, gene circuit-based sensors have primarily used optical proteins (e.g. fluorescent, colorimetric) as reporter outputs. This has limited the potential to measure multiple distinct signals. Here we present an electrochemical interface that allows measurement of multiple distinct reporter outputs within the same volume. To achieve this, we have developed a scalable system of reporter enzymes that convert sensor activation into sequence-specific cleavage of DNA. Upon liberation of the resulting ssDNA strands, an electrochemical signal is generated through base pairing at the surface of nanostructured microelectrodes coated in complementary DNA. We will discuss the development of this electrochemical interface and share proof-of-concept work that showcases a small molecule-regulated genetic switch and toehold switch-based sensors for the detection of resistance genes against the last line antibiotic colistin. We see this technology as an exciting new medium for the field of synthetic biology and one with the potential to drive further interdisciplinary interactions with materials, hardware and software.