Synthetic biology is the field of engineering biology inspired by engineering in computation, standardization, and construction to develop new devices composed of biological parts. Cell-free systems are emerging as abiotic platforms for high-throughput characterization and prototyping of natural and synthetic biological circuitries. The most common cell-free systems nowadays are transcription-translation (TXTL) cell-free systems which are made by combining cell lysate/extract plus reaction buffers. Although cell-free systems have multiple advantages over living cells, there are still obstacles to applying cell-free systems such as weak repression behavior.
Composition and functioning of biosensors in transcription-translation cell-free systems. (a) A Cell-free biosensor is composed of the cell-free reaction mix (cell lysate and reaction buffers) plus the DNA. (b) The addition of the chemical (inducer) produces GFP in this case by derepressing the promoter.
In a recent study, published in ACS synthetic biology, we explored different optimization ways to improve the weak repression in the cell-free system. We designed a simple biosensor responding to D-psicose through