Synthetic biosensing systems

An essential feature of synthetic biology devices is the conversion of signals from the exterior of the cell into specific cellular events such as the synthesis of a fluorescent protein. In the first synthetic gene circuits, signal transduction was accomplished via inducible or repressible transcription factors. Today, these rather simple transcription networks are the basis for the construction of more sophisticated devices that, for instance, couple artificial gene circuits with cellular pathways to create a biosensing moiety. In the future, completely artificial signaling pathways will give us the possibility to control cellular processes in a direct, precise and reliable way. At present, numerous pathway components such as receptors, adapters, scaffolds and their interactions with ligands and other signaling proteins have been already characterized and, in some cases, reengineered. In addition, important results have been obtained by rewiring pathways and building more complex gene networks-such as “cell phones” and ecosystems-based on synthetically induced cell-cell communication mechanisms. Furthermore, RNA-interference and light-dependent control of transcription factors have become new instruments to integrate different signals and better regulate protein synthesis. Overall, synthetic biology of sensing systems appears to be in continuous evolution. Nevertheless, rapid improvements on the available DNA-recombinant technology are essential to achieve, within few years, a full engineering of cell transduction pathways.