pH Feedback Lifecycles Programmed by Enzymatic Logic Gates Using Common Foods as Fuels.

Artificial temporal signaling systems, which mimic living out-of-equilibrium conditions, have made large progress. However, systems programmed by enzymatic reaction networks in multicomponent and unknown environments, and using biocompatible components remain a challenge. Herein, we demonstrate an approach to program temporal pH signals by enzymatic logic gates. They are realized by an enzymatic disaccharide-to-monosaccharide-to-sugar acid reaction cascade catalyzed by two metabolic chains: invertase-glucose oxidase and β-galactosidase-glucose oxidase, respectively. Lifetimes of the transient pH signal can be programmed from less than 15 min to more than 1 day. We study enzymatic kinetics of the reaction cascades and reveal the underlying regulatory mechanisms. Operating with all-food grade chemicals and coupling to self-regulating hydrogel, our system is quite robust to work in a complicated medium with unknown components and in a biocompatible fashion.