Engineering an active extracellular medium with DNA programs

Synthetic biology controls cell behaviour by engineering chemical reaction networks inside the cell. Here, we explore an alternative approach consisting in engineering reaction networks outside the cell that allow to control the chemical composition inside the cell. We do so by devising an active and programmable extracellular medium where human cells can grow and enzyme-based DNA molecular programs are functional. In particular, we demonstrate that a DNA autocatalytic network and a bistable switch remain active at 37 oC in the presence of living cells, illustrating that DNA detection down to 100 pM is possible in this context. Finally, we construct an internalization program that is capable of controlling the delivery of fluorescent DNA inside living cells. The program remains functional for 48 h and responsive for at least 6 h. We foresee that active extracellular media could be advantageously applied to in vitro biomolecular tracking, and further benefit tissue engineering or smart bandages.