Fig. 1: Interfacing cell-free biosensors with DNA strand displacement circuits expands and enhances their function.

(Upper) A cell-free biosensor typically activates when a target compound (input) binds to a protein transcription factor (sensor layer) that is configured to activate expression of a reporter construct (output layer). This results in the production of a detectable signal such as fluorescence. (Lower) Adding a downstream information processing layer before signal generation can enhance the performance and expand the function of cell-free biosensors by adding computational features such as logic processing and signal comparison. Here, this is implemented by wiring the biosensing output layer to produce a single-stranded RNA capable of activating toehold-mediated strand displacement circuits that generate signal.