Abstract
As an important branch of biosensors, gene circuit-based biosensors constructed based on synthetic biology concepts can sense specific substances to be measured and converted into specific signal outputs. Such sensors have great potential in the fields of biomanufacturing process monitoring, environmental monitoring, food safety, medical diagnosis, and monitoring. With the development of synthetic biology technology and the abundance of genetic components, more and more cell-free microbial sensors with different response mechanisms, logic gates, and logic loops have been developed. This review integrates the basic concepts of synthetic biology to comprehensively describe the design and engineering of synthetic biology gene circuits, an overview of synthetic biology based on cell-free systems (CFS), and the development of biosensors based on CFS. Emphasis is placed on the design concepts, construction principles, and applications of cell-free-based biosensors in the field of bioassay. We also discuss the new frontiers in the field and the challenges to be addressed.